1
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Sun X, Bai JK, Yang YD, Zhu KL, Liang JQ, Wang XY, Xiang JF, Hao X, Liang TL, Guan AJ, Wu NN, Gong HY. Controlled interconversion of macrocyclic atropisomers via defined intermediates. Nat Commun 2024; 15:6559. [PMID: 39095340 PMCID: PMC11297318 DOI: 10.1038/s41467-024-50739-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 07/18/2024] [Indexed: 08/04/2024] Open
Abstract
Macrocyclic conformations play a crucial role in regulating their properties. Our understanding of the determinants to control macrocyclic conformation interconversion is still in its infancy. Here we present a macrocycle, octamethyl cyclo[4](1,3-(4,6)-dimethylbenzene)[4]((4,6-benzene)(1,3-dicarboxylate) (OC-4), that can exist at 298 K as two stable atropisomers with C2v and C4v symmetry denoted as C2v-OC-4 and C4v-OC-4, respectively. Heating induces the efficient stepwise conversion of C2v- to C4v-OC-4 via a Cs-symmetric intermediate (Cs-OC-4). It differs from the typical transition state-mediated processes of simple C-C single bond rotations. Hydrolysis and further esterification with a countercation dependence promote the generation of C2v- and Cs-OC-4 from C4v-OC-4. In contrast to C2v-OC-4, C4v-OC-4 can bind linear guests to form pseudo-rotaxans, or bind C60 or C70 efficiently. The present study highlights the differences in recognition behavior that can result from conformational interconversion, as well as providing insights into the basic parameters that govern coupled molecular rotations.
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Affiliation(s)
- Xin Sun
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China
| | - Jin-Ku Bai
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China
| | - Yu-Dong Yang
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China
| | - Ke-Lin Zhu
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China
| | - Jia-Qi Liang
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China
| | - Xin-Yue Wang
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China
| | - Jun-Feng Xiang
- Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China
- University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Xiang Hao
- Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China
- University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Tong-Ling Liang
- Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China
- University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Ai-Jiao Guan
- Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China
- University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Ning-Ning Wu
- Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China
- University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Han-Yuan Gong
- College of Chemistry, Beijing Normal University, Beijing, 100875, PR China.
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2
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Nagami S, Kaguchi R, Akahane T, Harabuchi Y, Taniguchi T, Monde K, Maeda S, Ichikawa S, Katsuyama A. Photoinduced dual bond rotation of a nitrogen-containing system realized by chalcogen substitution. Nat Chem 2024; 16:959-969. [PMID: 38418536 DOI: 10.1038/s41557-024-01461-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 01/26/2024] [Indexed: 03/01/2024]
Abstract
Photoinduced concerted multiple-bond rotation has been proposed in some biological systems. However, the observation of such phenomena in synthetic systems, in other words, the synthesis of molecules that undergo photoinduced multiple-bond rotation upon photoirradiation, has been a challenge in the photochemistry field. Here we describe a chalcogen-substituted benzamide system that exhibits photoinduced dual bond rotation in heteroatom-containing bonds. Introduction of the chalcogen substituent into a sterically hindered benzamide system provides sufficient kinetic stability and photosensitivity to enable the photoinduced concerted rotation. The presence of two different substituents on the phenyl ring in the thioamide derivative enables the generation of a pair of enantiomers and E/Z isomers. Using these four stereoisomers as indicators of which bonds are rotated, we monitor the photoinduced C-N/C-C concerted bond rotation in the thioamide derivative depending on external stimuli such as temperature and photoirradiation. Theoretical calculations provide insight on the mechanism of this selective photoinduced C-N/C-C concerted rotation.
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Affiliation(s)
- Shotaro Nagami
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Rintaro Kaguchi
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Taichi Akahane
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Yu Harabuchi
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan
- JST, ERATO, Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Sapporo, Japan
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Tohru Taniguchi
- Frontier Research Center of Advanced Material and Life Science, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan
| | - Kenji Monde
- Frontier Research Center of Advanced Material and Life Science, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan
| | - Satoshi Maeda
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan
- JST, ERATO, Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Sapporo, Japan
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Satoshi Ichikawa
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
- Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan.
- Center for Research and Education on Drug Discovery, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
| | - Akira Katsuyama
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
- Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan.
- Center for Research and Education on Drug Discovery, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
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3
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Ruyet L, Roblick C, Häfliger J, Wang ZX, Stoffels TJ, Daniliuc CG, Gilmour R. Catalytic Ring Expanding Difluorination: An Enantioselective Platform to Access β,β-Difluorinated Carbocycles. Angew Chem Int Ed Engl 2024; 63:e202403957. [PMID: 38482736 DOI: 10.1002/anie.202403957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Indexed: 04/11/2024]
Abstract
Cyclic β,β-difluoro-carbonyl compounds have a venerable history as drug discovery leads, but limitations in the synthesis arsenal continue to impede chemical space exploration. This challenge is particularly acute in the arena of fluorinated medium rings where installing the difluoromethylene unit subtly alters the ring conformation by expanding the internal angle (∠C-CF2-C>∠C-CH2-C): this provides a handle to modulate physicochemistry (e.g. pKa). To reconcile this disparity, a highly modular ring expansion has been devised that leverages simple α,β-unsaturated esters and amides, and processes them to one-carbon homologated rings with concomitant geminal difluorination (6 to 10 membered rings, up to 95 % yield). This process is a rare example of the formal difluorination of an internal alkene and is enabled by sequential I(III)-enabled O-activation. Validation of enantioselective catalysis in the generation of unprecedented medium ring scaffolds is reported (up to 93 : 7 e.r.) together with X-ray structural analyses and product derivatization.
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Affiliation(s)
- Louise Ruyet
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
| | - Christoph Roblick
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
| | - Joel Häfliger
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
| | - Zi-Xuan Wang
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
| | - Tobias Jürgen Stoffels
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
| | - Constantin G Daniliuc
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
| | - Ryan Gilmour
- University of Münster, Institute for Organic Chemistry, Corrensstraße 36, 48149, Münster, Germany
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4
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Yang P, Liu HZ, Wang YS, Qi H, Wang LL, Wang BB, Xie XB. Synthesis and structure-activity relationship of novel thiazole aminoguanidines against MRSA and Escherichia coli. RSC Med Chem 2024; 15:1003-1014. [PMID: 38516595 PMCID: PMC10953494 DOI: 10.1039/d4md00017j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 02/22/2024] [Indexed: 03/23/2024] Open
Abstract
Novel lead thiazole aminoguanidines exhibited strong activity against Gram-positive bacteria. The potential targets of these substances are undecaprenyl diphosphate synthase (UPPS) and undecaprenyl diphosphate phosphatase (UPPP). Here, we report the synthesis and antibacterial evaluation of a library of thiazole aminoguanidines analogues, wherein the rotatable bond is inserted between the C2 position of thiazole and hydrophobic group. The molecular flexibility is increased, and new analogues with strong activity against MRSA and E. coli are produced. The best compound 4i showed rapid sterilization and low tendency to induce bacterial resistance. The IC50 of compound 4i to EcUPPS enzyme is 145 μmol L-1 (58 μg mL-1). Compound 4i can also inhibit and destroy bacterial biofilms. These thiazole aminoguanidines can be developed as potential therapeutic candidates in the future.
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Affiliation(s)
- Ping Yang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
| | - Hui-Zhong Liu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
| | - Ying-Si Wang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
| | - Hong Qi
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
| | - Ling-Ling Wang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
| | - Bei-Bei Wang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
| | - Xiao-Bao Xie
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangdong Detection Centre of Microbiology Guangzhou 510070 China
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5
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Fujita R, Ooka K, Wasada H, Ichikawa Y, Hosokawa S. First synthesis of (±)-halichonadins A-D. Org Biomol Chem 2024; 22:1901-1906. [PMID: 38352996 DOI: 10.1039/d4ob00088a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Described herein is the first total synthesis of a marine isocyanide terpene, (±)-halichonadin C. Our synthetic strategy features nitrile-to-isocyanide interconversion utilizing hypervalent iodine-promoted Hofmann rearrangement. This approach led to successful construction of an isocyanide group at the stereochemically encumbered C-6 position in (±)-halichonadin C. Furthermore, in accord with a scenario we propose for the biosynthesis of halichonadins A-D, (±)-halichonadin C was transformed to halichonadins A and B via the missing link intermediate, halichonadin isocyanate.
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Affiliation(s)
- Ryohei Fujita
- Department of Applied Chemistry, Faculty of Advanced Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Kaito Ooka
- Department of Applied Chemistry, Faculty of Advanced Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Hiroaki Wasada
- Faculty of Regional Studies, Regional Environmental Science, Gifu University, Japan
| | - Yoshiyasu Ichikawa
- Faculty of Science, Kochi University, Akebono-cho, Kochi 780-8520, Japan
| | - Seijiro Hosokawa
- Department of Applied Chemistry, Faculty of Advanced Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
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6
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Fontana C, de Meirelles JL, Verli H. Theoretical models of staurosporine and analogs uncover detailed structural information in biological solution. J Mol Graph Model 2024; 126:108653. [PMID: 37922640 DOI: 10.1016/j.jmgm.2023.108653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/12/2023] [Accepted: 10/12/2023] [Indexed: 11/07/2023]
Abstract
Staurosporine and its analogs (STA-analogs) are indolocarbazoles (ICZs) compounds able to inhibit kinase proteins in a non-specific way, while present antimicrobial and cytostatic properties. The knowledge of molecular features associated to the complexation, including the ligand shape in solution and thermodynamics of complexation, is substantial to the development of new bioactive ICZs with improved therapeutic properties. In this context, the empirical approach of GROMOS force field is able to accurately reproduce condensed phase physicochemical properties of molecular systems after parameterization. Hence, through parameterization under GROMOS force field and molecular simulations, we assessed STA-analogs dynamics in aqueous solution, as well as its interaction with water to probe conformational and structural features involved in complexation to therapeutic targets. The coexistence of multiple conformers observed in simulations, and confirmed by metadynamics calculations, expanding the conformational space knowledge of these ligands with potential implications in understanding the ligand conformational selection during complexation. Also, changes in availability to H-bonding concerning the different substituents and water can reflect on effects at complexation free energy due to variation at the desolvation energetic costs. Based on these results, we expect the obtained structural data provide systemic framework for rational chemical modification of STA-analogs.
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Affiliation(s)
- Crisciele Fontana
- Universidade Federal do Rio Grande do Sul, Centro de Biotecnologia, Av. Bento Gonçalves, 9500 (Caixa Postal 15005), Porto Alegre, CEP 91501-970, RS, Brazil
| | - João Luiz de Meirelles
- Universidade Federal do Rio Grande do Sul, Centro de Biotecnologia, Av. Bento Gonçalves, 9500 (Caixa Postal 15005), Porto Alegre, CEP 91501-970, RS, Brazil
| | - Hugo Verli
- Universidade Federal do Rio Grande do Sul, Centro de Biotecnologia, Av. Bento Gonçalves, 9500 (Caixa Postal 15005), Porto Alegre, CEP 91501-970, RS, Brazil.
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7
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Madinah R, Rusydi F, Fadilla RN, Khoirunisa V, Boli LSP, Saputro AG, Hassan NH, Ahmad A. First-Principles Study of the Dispersion Effects in the Structures and Keto-Enol Tautomerization of Curcumin. ACS OMEGA 2023; 8:34022-34033. [PMID: 37744805 PMCID: PMC10515353 DOI: 10.1021/acsomega.3c04907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Accepted: 08/18/2023] [Indexed: 09/26/2023]
Abstract
Noncovalent interactions, such as dispersion, play a significant role in the stability of flexible molecules, such as curcumin. This study revealed the importance of dispersion correction in the structure and keto-enol tautomerization of curcumin, which has rarely been addressed in computational studies. We rigorously constructed all possible unique curcumin conformers in the enol and keto forms within the first-principles framework. Regardless of the different environments, we carefully explained the agreement between the computational geometry (in the gas phase) and the experimental measurement (in the polymorph) by using dispersion correction. The calculation results for the aqueous solution of conformational abundance, thermochemistry, and reaction kinetics support the experimental observations after considering the dispersion correction. The study also suggests a water-catalyzed mechanism for keto-enol tautomerization, where dispersion correction plays a role in decreasing the energy barrier and making the keto form thermochemically and kinetically favorable. Our results could be helpful in future computational studies to find a method for increasing the aqueous solubility of curcumin; hence, the potential of curcumin as a multifunctional medicine can be fully achieved.
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Affiliation(s)
- Roichatul Madinah
- Department
of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
| | - Febdian Rusydi
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Department
of Physics, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
| | - Rizka N. Fadilla
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Department
of Precision Engineering, Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan
| | - Vera Khoirunisa
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Department
of Engineering Physics, Institut Teknologi
Sumatera, Jl. Terusan Ryacudu, Lampung Selatan 35365, Indonesia
| | - Lusia S. P. Boli
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Advanced
Functional Materials Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung, Bandung 40132, Indonesia
- Physics Study
Program, Faculty of Mathematics and Natural Sciences, Universitas Jendral Soedirman, Purwokerto 53122, Indonesia
| | - Adhitya G. Saputro
- Advanced
Functional Materials Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung, Bandung 40132, Indonesia
| | - Nur H. Hassan
- Department
of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
| | - Azizan Ahmad
- Department
of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
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8
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Zhao H, Brånalt J, Perry M, Tyrchan C. The Role of Allylic Strain for Conformational Control in Medicinal Chemistry. J Med Chem 2023. [PMID: 37285219 DOI: 10.1021/acs.jmedchem.3c00446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
It is axiomatic in medicinal chemistry that optimization of the potency of a small molecule at a macromolecular target requires complementarity between the ligand and target. In order to minimize the conformational penalty on binding, both enthalpically and entropically, it is therefore preferred to have the ligand preorganized in the bound conformation. In this Perspective, we highlight the role of allylic strain in controlling conformational preferences. Allylic strain was originally described for carbon-based allylic systems, but the same principles apply to other types of structure with sp2 or pseudo-sp2 arrangements. These systems include benzylic (including heteroaryl methyl) positions, amides, N-aryl groups, aryl ethers, and nucleotides. We have derived torsion profiles from small molecule X-ray structures for these systems. Through multiple examples, we show how these effects have been applied in drug discovery and how they can be used prospectively to influence conformation in the design process.
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Affiliation(s)
- Hongtao Zhao
- Medicinal Chemistry, Research and Early Development, Respiratory and Immunology (R&I), BioPharmaceuticals R&D, AstraZeneca, Gothenburg 43183, Sweden
| | - Jonas Brånalt
- Medicinal Chemistry, Research and Early Development, Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg 43183, Sweden
| | - Matthew Perry
- Medicinal Chemistry, Research and Early Development, Respiratory and Immunology (R&I), BioPharmaceuticals R&D, AstraZeneca, Gothenburg 43183, Sweden
| | - Christian Tyrchan
- Medicinal Chemistry, Research and Early Development, Respiratory and Immunology (R&I), BioPharmaceuticals R&D, AstraZeneca, Gothenburg 43183, Sweden
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9
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Dewis LI, Rudrakshula M, Williams C, Chiarparin E, Myers EL, Butts CP, Aggarwal VK. Conformationally Controlled sp 3 -Hydrocarbon-Based α-Helix Mimetics. Angew Chem Int Ed Engl 2023; 62:e202301209. [PMID: 37017133 PMCID: PMC10953326 DOI: 10.1002/anie.202301209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 04/06/2023]
Abstract
With over 60 % of protein-protein interfaces featuring an α-helix, the use of α-helix mimetics as inhibitors of these interactions is a prevalent therapeutic strategy. However, methods to control the conformation of mimetics, thus enabling maximum efficacy, can be restrictive. Alternatively, conformation can be controlled through the introduction of destabilizing syn-pentane interactions. This tactic, which is often adopted by Nature, is not a common feature of lead optimization owing to the significant synthetic effort required. Through assembly-line synthesis with NMR and computational analysis, we have shown that alternating syn-anti configured contiguously substituted hydrocarbons, by avoiding syn-pentane interactions, adopt well-defined conformations that present functional groups in an arrangement that mimics the α-helix. The design of a p53 mimetic that binds to Mdm2 with moderate to good affinity, demonstrates the therapeutic promise of these scaffolds.
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Affiliation(s)
- Lydia I. Dewis
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | | | | | | | - Eddie L. Myers
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
- School of Biological and Chemical SciencesUniversity of GalwayUniversity RoadGalwayIreland
| | - Craig P. Butts
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
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10
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Naseem M, Asghar S, Farooq U, Lakhani A, Altaf Y, Hashmi MA. Determination of the Absolute Configuration of Ballonigrin Lactone A Using Density Functional Theory Calculations. ACS OMEGA 2023; 8:1923-1928. [PMID: 36687041 PMCID: PMC9850775 DOI: 10.1021/acsomega.2c03858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 12/21/2022] [Indexed: 06/17/2023]
Abstract
We report the determination of the absolute configuration of a diterpenoid, namely, ballonigrin lactone A (BLA), by comparison of the computed optical rotations, [α]D, of its two diastereomers using density functional theory (DFT) calculations to the experimental [α]D value of +22.4. One of the diastereomers having configurations 4S, 5R, 6S, 10S, 15S was named "α-BLA," and the other one with configuration 4S, 5R, 6S, 10S, 15R was called "β-BLA". Six conformers for each diastereomer (α-BLA and β-BLA) of BLA were identified through their conformational analysis. [α]D values of these six conformations for each diastereomer were calculated using DFT at the mPW1PW91/6-311G(d,p)/SMDChloroform level of theory, leading to the conformationally averaged [α]D values of -96.8 for α-BLA and +65.1 for β-BLA. Thus, it was found that the experimental [α]D value of +22.4 was of 4S, 5R, 6S, 10S, 15R, i.e., β-BLA. Experimental and computed nuclear magnetic resonance (NMR) data were also compared, and this comparison was in accordance with the conclusion drawn from the comparison of [α]D values. Finally, the results were augmented with the calculation of the DP4 analysis, and the probability obtained also endorsed our earlier calculations.
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Affiliation(s)
- Misbah Naseem
- Department
of Chemistry, Division of Science & Technology, University of Education, 54770 Lahore, Pakistan
| | - Saleha Asghar
- Department
of Chemistry, Division of Science & Technology, University of Education, 54770 Lahore, Pakistan
| | - Umar Farooq
- Department
of Chemistry, COMSATS University Islamabad,
Abbottabad Campus, 22060 Abbottabad, Pakistan
| | - Ahmed Lakhani
- Department
of Biomedical and Health Sciences, Calumet
College of St. Joseph, 2400, New York Avenue, Whiting, Indiana 46394, United States
| | - Yasir Altaf
- Department
of Chemistry, Division of Science & Technology, University of Education, 54770 Lahore, Pakistan
| | - Muhammad Ali Hashmi
- Department
of Chemistry, Division of Science & Technology, University of Education, 54770 Lahore, Pakistan
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11
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Towards the engineering of a photon-only two-stroke rotary molecular motor. Nat Commun 2022; 13:6433. [PMID: 36307476 PMCID: PMC9616945 DOI: 10.1038/s41467-022-33695-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 09/27/2022] [Indexed: 12/25/2022] Open
Abstract
The rational engineering of photoresponsive materials, e.g., light-driven molecular motors, is a challenging task. Here, we use structure-related design rules to prepare a prototype molecular rotary motor capable of completing an entire revolution using, exclusively, the sequential absorption of two photons; i.e., a photon-only two-stroke motor. The mechanism of rotation is then characterised using a combination of non-adiabatic dynamics simulations and transient absorption spectroscopy measurements. The results show that the rotor moiety rotates axially relative to the stator and produces, within a few picoseconds at ambient T, an intermediate with the same helicity as the starting structure. We discuss how such properties, that include a 0.25 quantum efficiency, can help overcome the operational limitations of the classical overcrowded alkene designs.
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12
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McTiernan TJ, Diaz DB, Saunders GJ, Sprang F, Yudin AK. Navigating complex peptide structures using macrocycle conformational maps. RSC Chem Biol 2022; 3:739-747. [PMID: 35755184 PMCID: PMC9175111 DOI: 10.1039/d2cb00016d] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 04/14/2022] [Indexed: 11/21/2022] Open
Abstract
Identification of turn motifs that are stabilized by intramolecular hydrogen bonds can be useful in describing the conformation of peptide systems. However, this approach is somewhat insufficient for cyclic peptides because peptide regions that are not positioned within a hydrogen bond can be left with no description. Furthermore, non-regular secondary structures and other rarely-observed conformations can be left without detailed evaluation. Herein, we describe “higher-order” ϕ/ψ plots termed macrocycle conformational maps (MCMs) as a tool for evaluating and comparing the conformations of a series of structurally related macrocyclic peptides. Identification of turn motifs that are stabilized by hydrogen bonds can be useful in describing the conformation of peptides. Herein, we describe “higher-order” ϕ/ψ plots termed macrocycle conformational maps (MCMs) as a tool to evaluate and compare the conformations of related macrocycles.![]()
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Affiliation(s)
- Timothy J McTiernan
- Davenport Research Laboratories, Department of Chemistry, University of Toronto Toronto ON M5S 3H6 Canada
| | - Diego B Diaz
- Davenport Research Laboratories, Department of Chemistry, University of Toronto Toronto ON M5S 3H6 Canada
| | - George J Saunders
- Davenport Research Laboratories, Department of Chemistry, University of Toronto Toronto ON M5S 3H6 Canada
| | - Fiona Sprang
- Davenport Research Laboratories, Department of Chemistry, University of Toronto Toronto ON M5S 3H6 Canada
| | - Andrei K Yudin
- Davenport Research Laboratories, Department of Chemistry, University of Toronto Toronto ON M5S 3H6 Canada
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13
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Guo L, Dutton OJ, Kucukdisli M, Davy M, Wagnières O, Butts CP, Myers EL, Aggarwal VK. Conformationally Controlled Linear and Helical Hydrocarbons Bearing Extended Side Chains. J Am Chem Soc 2021; 143:16682-16692. [PMID: 34590479 PMCID: PMC7612001 DOI: 10.1021/jacs.1c07778] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Conformationally controlled flexible molecules are ideal for applications in medicine and materials, where shape matters but an ability to adapt to multiple and changing environments is often required. The conformation of flexible hydrocarbon chains bearing contiguous methyl substituents is controlled through the avoidance of syn-pentane interactions: alternating syn-anti isomers adopt a linear conformation while all-syn isomers adopt a helical conformation. From a simple diamond lattice analysis, larger substituents, which would be required for most potential applications, result in significant and unavoidable syn-pentane interactions, suggesting substantially reduced conformational control. Through a combination of computation, synthesis, and NMR analysis, we have identified a selection of substitution patterns that allow large groups to be incorporated on conformationally controlled linear and helical hydrocarbon chains. Surprisingly, when the methyl substituents of alternating syn-anti hydrocarbons are replaced with acetoxyethyl groups, the main chain of almost 95% of the population of molecules adopt a linear conformation. Here, the side chains adopt nonideal eclipsed conformations with the main chain, thus minimizing syn-pentane interactions. In the case of all-syn hydrocarbons, concurrent removal of some methyl groups on the main chain adjacent to the large substituents is required to maintain a high population of molecules adopting a helical conformation. This information can now be used to design flexible hydrocarbon chains displaying functional groups in a defined relative orientation for multivalent binding or cooperative reactivity, for example, in targeting the interfaces defined by disease-relevant protein-protein interactions.
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Affiliation(s)
- Lin Guo
- School of Chemistry, University of Bristol, BS8 1TS, Bristol, UK
| | - Oliver J. Dutton
- School of Chemistry, University of Bristol, BS8 1TS, Bristol, UK
| | - Murat Kucukdisli
- School of Chemistry, University of Bristol, BS8 1TS, Bristol, UK
| | - Matthew Davy
- School of Chemistry, University of Bristol, BS8 1TS, Bristol, UK
| | | | - Craig P. Butts
- School of Chemistry, University of Bristol, BS8 1TS, Bristol, UK
| | - Eddie L. Myers
- School of Chemistry, NUI Galway, Galway H91 TK33, Ireland
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14
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Cohen Y, Augustin AU, Levy L, Jones PG, Werz DB, Marek I. Regio- and Diastereoselective Copper-Catalyzed Carbomagnesiation for the Synthesis of Penta- and Hexa-Substituted Cyclopropanes. Angew Chem Int Ed Engl 2021; 60:11804-11808. [PMID: 33742749 DOI: 10.1002/anie.202102509] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Indexed: 11/07/2022]
Abstract
Despite the highly strained nature of cyclopropanes possessing three vicinal quaternary carbon stereocenters, the regio- and diastereoselective copper-catalyzed carbomagnesiation reaction of cyclopropenes provides an easy and efficient access to these novel persubstituted cyclopropyl cores with a complete regio- and diastereoselectivity.
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Affiliation(s)
- Yair Cohen
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa, 3200009, Israel
| | - André U Augustin
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa, 3200009, Israel
| | - Laura Levy
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa, 3200009, Israel
| | - Peter G Jones
- Technische Universität Braunschweig, Institute of Inorganic and Analytical Chemistry, Hagenring 30, 38106, Braunschweig, Germany
| | - Daniel B Werz
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106, Braunschweig, Germany
| | - Ilan Marek
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa, 3200009, Israel
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15
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Cohen Y, Augustin AU, Levy L, Jones PG, Werz DB, Marek I. Regio‐ and Diastereoselective Copper‐Catalyzed Carbomagnesiation for the Synthesis of Penta‐ and Hexa‐Substituted Cyclopropanes. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102509] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Yair Cohen
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Technion City Haifa 3200009 Israel
| | - André U. Augustin
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Technion City Haifa 3200009 Israel
| | - Laura Levy
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Technion City Haifa 3200009 Israel
| | - Peter G. Jones
- Technische Universität Braunschweig Institute of Inorganic and Analytical Chemistry Hagenring 30 38106 Braunschweig Germany
| | - Daniel B. Werz
- Technische Universität Braunschweig Institute of Organic Chemistry Hagenring 30 38106 Braunschweig Germany
| | - Ilan Marek
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Technion City Haifa 3200009 Israel
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16
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Diaz DB, Appavoo SD, Bogdanchikova AF, Lebedev Y, McTiernan TJ, Dos Passos Gomes G, Yudin AK. Illuminating the dark conformational space of macrocycles using dominant rotors. Nat Chem 2021; 13:218-225. [PMID: 33589789 DOI: 10.1038/s41557-020-00620-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 12/07/2020] [Indexed: 02/06/2023]
Abstract
Three-dimensional conformation is the primary determinant of molecular properties. The thermal energy available at room temperature typically equilibrates the accessible conformational states. Here, we introduce a method for isolating unique and previously understudied conformations of macrocycles. The observation of unusual conformations of 16- to 22-membered rings has been made possible by controlling their interconversion using dominant rotors, which represent tunable atropisomeric constituents with relatively high rotational barriers. Density functional theory and in situ NMR measurements suggest that dominant rotor candidates for the amino-acid-based structures considered here should possess a rotational energy barrier of at least 25 kcal mol-1. Notable differences in the geometries of the macrocycle conformations were identified by NMR spectroscopy and X-ray crystallography. There is evidence that amino acid residues can be forced into rare turn motifs not observed in the corresponding linear counterparts and homodetic rings. These findings should unlock new avenues for studying the conformation-activity relationships of bioactive molecules.
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Affiliation(s)
- Diego B Diaz
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Solomon D Appavoo
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | | | - Yury Lebedev
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | | | - Gabriel Dos Passos Gomes
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.,Department of Computer Science, University of Toronto, Toronto, Ontario, Canada
| | - Andrei K Yudin
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.
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17
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Sales ES, Dos Santos GM, Mandle RJ, Costa WC, Bechtold IH, Gonçalves IL, Eifler-Lima VL, Merlo AA. Insight into Out-of-Layer Fluctuations in the Smectic A Stability of 3,5-Diarylisoxazole Liquid Crystals. Chemphyschem 2020; 21:1408-1419. [PMID: 32463550 DOI: 10.1002/cphc.202000276] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/12/2020] [Indexed: 11/11/2022]
Abstract
Polar-terminated 3,5-diarylisoxazole liquid crystals (ILCs) were synthetized and characterized. ILCs are composed by rigid core 3,5-diarylisoxazol, alkyl chain and polar-terminated flexible spacer. Hydroxyl-, ketal- and 1,2-diol-terminated ILCs rendered smectic C and A mesophase, while bromine-terminated ILCs showed smectic A and B mesophase, for monosubstituted and linear ILCs. For branched alkyl chain monotropic SmA was detected and for disubstituted ILCs no mesophase was detected. Out-of-layer fluctuations (OLFs) are discussed based on X-ray diffraction date and textures. The OLFs are dependent on the bromine atom hardness, hydrogen bonding through collective actions and conformational effects at the interface between layers. Smectic translational order parameter (TOP) Σ was also obtained for orientated bromine- and hydroxyl-terminated ILCs and related it with OLFs. For 1,2-diol-terminated ILCs two SmC sublayers were founded, probably related to the intramolecular hydrogen bond favoring the 5-membered and 6-membered formation.
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Affiliation(s)
- Eric S Sales
- Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501970, RS, Brazil
| | - Gabriel M Dos Santos
- Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501970, RS, Brazil
| | - Richard J Mandle
- Department of Chemistry, University of York, York, United Kingdom.,School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - Wallison C Costa
- Department of Physics, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Ivan H Bechtold
- Department of Physics, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Itamar L Gonçalves
- Faculty of Pharmacy, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Vera L Eifler-Lima
- Faculty of Pharmacy, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Aloir A Merlo
- Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501970, RS, Brazil
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18
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Lee S, Ghosh S, Jana S, Robertson N, Tate CG, Vaidehi N. How Do Branched Detergents Stabilize GPCRs in Micelles? Biochemistry 2020; 59:2125-2134. [PMID: 32437610 PMCID: PMC7302508 DOI: 10.1021/acs.biochem.0c00183] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
The
structural and functional properties of G protein-coupled receptors
(GPCRs) are often studied in a detergent micellar environment, but
many GPCRs tend to denature or aggregate in short alkyl chain detergents.
In our previous work [Lee, S., et al. (2016) J. Am. Chem.
Soc.138, 15425–15433], we showed
that GPCRs in alkyl glucosides were highly dynamic, resulting in the
penetration of detergent molecules between transmembrane α-helices,
which is the initial step in receptor denaturation. Although this
was not observed for GPCRs in dodecyl maltoside (DDM, also known as
lauryl maltoside), even this detergent is not mild enough to preserve
the integrity of many GPCRs during purification. Lauryl maltose neopentylglycol
(LMNG) detergents have been found to have significant advantages for
purifying GPCRs in a native state as they impart more stability to
the receptor than DDM. To gain insights into how they stabilize GPCRs,
we used atomistic molecular dynamics simulations of wild type adenosine
A2A receptor (WT-A2AR), thermostabilized A2AR (tA2AR), and wild type β2-adrenoceptor
(β2AR) in a variety of detergents (LMNG, DMNG, OGNG,
and DDM). Analysis of molecular dynamics simulations of tA2AR in LMNG, DMNG, and OGNG showed that this series of detergents exhibited
behavior very similar to that of an analogous series of detergents
DDM, DM, and OG in our previous study. However, there was a striking
difference upon comparison of the behavior of LMNG to that of DDM.
LMNG showed considerably less motion than DDM, which resulted in the
enhanced density of the aliphatic chains around the hydrophobic regions
of the receptor and considerably more hydrogen bond formation between
the head groups. This contributed to enhanced interaction energies
between both detergent molecules and between the receptor and detergent,
explaining the enhanced stability of GPCRs purified in this detergent.
Branched detergents occlude between transmembrane helices and reduce
their flexibility. Our results provide a rational foundation to develop
detergent variants for stabilizing membrane proteins.
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Affiliation(s)
- Sangbae Lee
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
| | - Soumadwip Ghosh
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
| | - Suvamay Jana
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
| | - Nathan Robertson
- Heptares Therapeutics Ltd., BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, U.K
| | - Christopher G Tate
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, U.K
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
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19
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Pradeilles JA, Zhong S, Baglyas M, Tarczay G, Butts CP, Myers EL, Aggarwal VK. Odd-even alternations in helical propensity of a homologous series of hydrocarbons. Nat Chem 2020; 12:475-480. [PMID: 32123339 DOI: 10.1038/s41557-020-0429-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 01/24/2020] [Indexed: 11/09/2022]
Abstract
Odd and even homologues of some n-alkane-based systems are known to exhibit notably different trends in solid-state properties; a well-known illustration is the zigzag plot of their melting point versus chain length. Odd-even effects in the solid state often arise from intermolecular interactions that involve fully extended molecules. These effects have also been observed in less condensed phases, such as self-assembled monolayers; however, the origins of these effects in such systems can be difficult to determine. Here we combined NMR and computational analysis to show that all-syn contiguously methyl-substituted hydrocarbons, with chain lengths from C6 to C11, exhibit a dramatic odd-even effect in helical propensity. The even- and odd-numbered hydrocarbons populate regular and less-controlled helical conformations, respectively. This knowledge will guide the design of helical hydrocarbons as rigid scaffolds or as hydrophobic components in soft materials.
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Affiliation(s)
| | - Siying Zhong
- School of Chemistry, University of Bristol, Bristol, UK
| | - Márton Baglyas
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.,MTA-ELTE, Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, Eötvös University, Budapest, Hungary
| | - György Tarczay
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.,MTA-ELTE, Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, Eötvös University, Budapest, Hungary
| | - Craig P Butts
- School of Chemistry, University of Bristol, Bristol, UK.
| | - Eddie L Myers
- School of Chemistry, National University of Ireland Galway, Galway, Ireland.
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20
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Sanford AB, Tollefson EJ, Jarvo ER. Stereospecific Cross-Coupling Reactions Provide Conformationally-Biased Arylalkanes with Anti-Leukemia Activity. Isr J Chem 2020; 60:402-405. [PMID: 33442068 PMCID: PMC7799436 DOI: 10.1002/ijch.201900071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 08/15/2019] [Indexed: 11/07/2022]
Abstract
A focused small library of carbamates and alcohols was prepared employing stereospecific Kumada-ring opening reactions of tetrahydropyrans. The core framework of the library members is acyclic and incorporates 1,3-substituents, to provide a conformational bias in avoiding syn-pentane interactions. A new compound with micromolar activity against MOLT-4, CCRF-CEM, and HL-60(TB) leukemia cell lines was identified from this series.
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Affiliation(s)
- Amberly B Sanford
- Department of Chemistry, University of California, Irvine, Natural Sciences II, Irvine, CA, 92697
| | - Emily J Tollefson
- Department of Chemistry, University of California, Irvine, Natural Sciences II, Irvine, CA, 92697
| | - Elizabeth R Jarvo
- Department of Chemistry, University of California, Irvine, Natural Sciences II, Irvine, CA, 92697
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21
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Jo M, Lee D, Kwak YS. Rapid Access to the Structural Core of Aflavinines via Stereoselective Tandem Intramolecular Diels-Alder Cycloaddition Controlled by the Allylic 1,3-Strain. Org Lett 2019; 21:6529-6533. [PMID: 31368715 DOI: 10.1021/acs.orglett.9b02457] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An expedient route to access the functionalized structural core of aflavinines has been developed starting from three readily available fragments over 12 steps in 29.1% overall yield without using any transition metal catalysis. The key feature of this approach is a tandem intramolecular Diels-Alder cycloaddition to complete the hexacyclic framework with the correct stereochemistry and all the requisite structural elements in place to achieve the total synthesis of aflavinine and its congeners.
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Affiliation(s)
- Minmi Jo
- College of Pharmacy , Korea University , Sejong 30019 , Republic of Korea
| | - Dongjoo Lee
- College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST) , Ajou University , Suwon 16499 , Republic of Korea
| | - Young-Shin Kwak
- College of Pharmacy , Korea University , Sejong 30019 , Republic of Korea
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22
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Appavoo SD, Huh S, Diaz DB, Yudin AK. Conformational Control of Macrocycles by Remote Structural Modification. Chem Rev 2019; 119:9724-9752. [DOI: 10.1021/acs.chemrev.8b00742] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Solomon D. Appavoo
- Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada M5S 3H6
| | - Sungjoon Huh
- Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada M5S 3H6
| | - Diego B. Diaz
- Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada M5S 3H6
| | - Andrei K. Yudin
- Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada M5S 3H6
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23
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Morimoto J, Fukuda Y, Kuroda D, Watanabe T, Yoshida F, Asada M, Nakamura T, Senoo A, Nagatoishi S, Tsumoto K, Sando S. A Peptoid with Extended Shape in Water. J Am Chem Soc 2019; 141:14612-14623. [DOI: 10.1021/jacs.9b04371] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jumpei Morimoto
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Yasuhiro Fukuda
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Daisuke Kuroda
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Takumu Watanabe
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Fumihiko Yoshida
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Mizue Asada
- Department of Materials Molecular Science, Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki 444-8585, Japan
| | - Toshikazu Nakamura
- Department of Materials Molecular Science, Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki 444-8585, Japan
| | - Akinobu Senoo
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Satoru Nagatoishi
- Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Kouhei Tsumoto
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Shinsuke Sando
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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24
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Bentler P, Bergander K, Daniliuc CG, Mück‐Lichtenfeld C, Jumde RP, Hirsch AKH, Gilmour R. Inverting Small Molecule-Protein Recognition by the Fluorine Gauche Effect: Selectivity Regulated by Multiple H→F Bioisosterism. Angew Chem Int Ed Engl 2019; 58:10990-10994. [PMID: 31157945 PMCID: PMC6771710 DOI: 10.1002/anie.201905452] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 05/31/2019] [Indexed: 12/31/2022]
Abstract
Fluorinated motifs have a venerable history in drug discovery, but as C(sp3 )-F-rich 3D scaffolds appear with increasing frequency, the effect of multiple bioisosteric changes on molecular recognition requires elucidation. Herein we demonstrate that installation of a 1,3,5-stereotriad, in the substrate for a commonly used lipase from Pseudomonas fluorescens does not inhibit recognition, but inverts stereoselectivity. This provides facile access to optically active, stereochemically well-defined organofluorine compounds (up to 98 % ee). Whilst orthogonal recognition is observed with fluorine, the trend does not hold for the corresponding chlorinated substrates or mixed halogens. This phenomenon can be placed on a structural basis by considering the stereoelectronic gauche effect inherent to F-C-C-X systems (σ→σ*). Docking reveals that this change in selectivity (H versus F) with a common lipase results from inversion in the orientation of the bound substrate being processed as a consequence of conformation. This contrasts with the stereochemical interpretation of the biogenetic isoprene rule, whereby product divergence from a common starting material is also a consequence of conformation, albeit enforced by two discrete enzymes.
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Affiliation(s)
- Patrick Bentler
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität MünsterCorrensstraße 4048149MünsterGermany
| | - Klaus Bergander
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität MünsterCorrensstraße 4048149MünsterGermany
| | - Constantin G. Daniliuc
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität MünsterCorrensstraße 4048149MünsterGermany
| | - Christian Mück‐Lichtenfeld
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität MünsterCorrensstraße 4048149MünsterGermany
| | - Ravindra P. Jumde
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI)Department of Drug Design and OptimizationUniversity Campus E8.166123SaarbrückenGermany
| | - Anna K. H. Hirsch
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI)Department of Drug Design and OptimizationUniversity Campus E8.166123SaarbrückenGermany
- Department of PharmacySaarland University66123SaarbrückenGermany
| | - Ryan Gilmour
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität MünsterCorrensstraße 4048149MünsterGermany
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25
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Bentler P, Bergander K, Daniliuc CG, Mück‐Lichtenfeld C, Jumde RP, Hirsch AKH, Gilmour R. Inverting Small Molecule–Protein Recognition by the Fluorine
Gauche
Effect: Selectivity Regulated by Multiple H→F Bioisosterism. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905452] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Patrick Bentler
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - Klaus Bergander
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - Constantin G. Daniliuc
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - Christian Mück‐Lichtenfeld
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - Ravindra P. Jumde
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI)Department of Drug Design and Optimization University Campus E8.1 66123 Saarbrücken Germany
| | - Anna K. H. Hirsch
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI)Department of Drug Design and Optimization University Campus E8.1 66123 Saarbrücken Germany
- Department of PharmacySaarland University 66123 Saarbrücken Germany
| | - Ryan Gilmour
- Organisch Chemisches InstitutWestfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
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26
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Qi Y, Volmer DA. Rapid mass spectral fingerprinting of complex mixtures of decomposed lignin: Data-processing methods for high-resolution full-scan mass spectra. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33 Suppl 1:2-10. [PMID: 30076644 DOI: 10.1002/rcm.8254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 07/19/2018] [Accepted: 07/26/2018] [Indexed: 06/08/2023]
Abstract
Lignin is the second most abundant natural biopolymer and its wastes are significant sources for renewable chemicals as an alternative to conventional fossil fuels. Consequently, chemical characterization methods are required to assess the content of valuable chemicals contained in these complex lignin wastes. This short overview summarizes rapid data-processing methods developed in our laboratory for application to full-scan raw data from high-resolution mass spectrometry experiments of decomposed lignin samples. The discussed graphical and statistical methods support the initial classification and elucidation of the main structural features of the lignin components without the need for time-consuming tandem mass spectrometry analyses.
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Affiliation(s)
- Yulin Qi
- Department of Chemistry, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Dietrich A Volmer
- Department of Chemistry, Humboldt-Universität zu Berlin, Berlin, Germany
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27
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Yu H, Lee R, Kim H, Lee D. Lewis Acid-Promoted Regio- and Diastereoselective Cross-Coupling of Aryl-Substituted 1,2-Diols and Boronic Acids. J Org Chem 2019; 84:3566-3578. [PMID: 30786205 DOI: 10.1021/acs.joc.9b00209] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A Lewis acid-promoted highly regio- and diastereoselective C(sp3)-C(sp2) cross-coupling reaction between unprotected aryl-substituted 1,2-diols and styryl-, aryl-, heteroaryl-, and polyarylboronic acids has been developed in a one-pot procedure. The regioselective opening of aryl-substituted cyclic boronic esters promoted by a Lewis acid followed by subsequent intramolecular 1,4-transfer of the carbon ligand from boron to a resonance-stabilized benzylic carbenium ion minimizing the allylic 1,3-strain in a stereoselective fashion led to the corresponding α-substituted syn-phenylethyl alcohols. The synthetic utility of the method was illustrated by a short and efficient enantioselective synthesis of cherylline diethyl ether (-)-16.
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Affiliation(s)
- Heesun Yu
- College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST) , Ajou University , 206 Worldcup-ro , Yeongtong-gu, Suwon 16499 , Republic of Korea
| | - Ryangha Lee
- College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST) , Ajou University , 206 Worldcup-ro , Yeongtong-gu, Suwon 16499 , Republic of Korea
| | - Hyoungsu Kim
- College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST) , Ajou University , 206 Worldcup-ro , Yeongtong-gu, Suwon 16499 , Republic of Korea
| | - Dongjoo Lee
- College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST) , Ajou University , 206 Worldcup-ro , Yeongtong-gu, Suwon 16499 , Republic of Korea
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28
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Lenci E, Menchi G, Saldívar-Gonzalez FI, Medina-Franco JL, Trabocchi A. Bicyclic acetals: biological relevance, scaffold analysis, and applications in diversity-oriented synthesis. Org Biomol Chem 2019; 17:1037-1052. [DOI: 10.1039/c8ob02808g] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The chemoinformatics analysis of fused, spiro, and bridged bicyclic acetals is instrumental for the DOS of natural product-inspired molecular collections.
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Affiliation(s)
- Elena Lenci
- Department of Chemistry “Ugo Schiff”
- University of Florence
- 50019 Sesto Fiorentino
- Italy
| | - Gloria Menchi
- Department of Chemistry “Ugo Schiff”
- University of Florence
- 50019 Sesto Fiorentino
- Italy
- Interdepartmental Center for Preclinical Development of Molecular Imaging (CISPIM)
| | - Fernanda I. Saldívar-Gonzalez
- School of Chemistry
- Department of Pharmacy
- Universidad Nacional Autónoma de México
- Avenida Universidad 3000
- Mexico City 04510
| | - José L. Medina-Franco
- School of Chemistry
- Department of Pharmacy
- Universidad Nacional Autónoma de México
- Avenida Universidad 3000
- Mexico City 04510
| | - Andrea Trabocchi
- Department of Chemistry “Ugo Schiff”
- University of Florence
- 50019 Sesto Fiorentino
- Italy
- Interdepartmental Center for Preclinical Development of Molecular Imaging (CISPIM)
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29
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Ravi A, Krishnarao PS, Shumilova TA, Khrustalev VN, Rüffer T, Lang H, Kataev EA. Cation Molecular Exchanger Based on a Conformational Hinge. Org Lett 2018; 20:6211-6214. [DOI: 10.1021/acs.orglett.8b02687] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Anil Ravi
- Institute of Chemistry, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | | | - Tatiana A. Shumilova
- Institute of Chemistry, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | - Victor N. Khrustalev
- National Research Center Kurchatov Institute, Acad Kurchatov Square 1, 123182 Moscow, Russian Federation
- Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklay Street 6, 117198 Moscow, Russian Federation
| | - Tobias Rüffer
- Institute of Chemistry, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | - Heinrich Lang
- Institute of Chemistry, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | - Evgeny A. Kataev
- Institute of Chemistry, Technische Universität Chemnitz, 09107 Chemnitz, Germany
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30
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Aufiero M, Gilmour R. Informing Molecular Design by Stereoelectronic Theory: The Fluorine Gauche Effect in Catalysis. Acc Chem Res 2018; 51:1701-1710. [PMID: 29894155 DOI: 10.1021/acs.accounts.8b00192] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The axioms of stereoelectronic theory constitute an atlas to navigate the contours of molecular space. All too rarely lauded, the advent and development of stereoelectronic theory has been one of organic chemistry's greatest triumphs. Inevitably, however, in the absence of a comprehensive treatise, many of the field's pioneers do not receive the veneration that they merit. Rather their legacies are the stereoelectronic pillars that persist in teaching and research. This ubiquity continues to afford practitioners of organic chemistry with an abundance of opportunities for creative endeavor in reaction design, in conceiving novel activation modes, in preorganizing intermediates, or in stabilizing productive transition states and products. Antipodal to steric governance, which mitigates destabilizing nonbonding interactions, stereoelectronic control allows well-defined, often complementary, conformations to be populated. Indeed, the prevalence of stabilizing hyperconjugative interactions in biosynthetic processes renders this approach to molecular preorganization decidedly biomimetic and, by extension, expansive. In this Account, the evolution and application of a simple donor-acceptor model based on the fluorine gauche effect is delineated. Founded on reinforcing hyperconjugative interactions involving C(sp3)-H bonding orbitals and C(sp3)-X antibonding orbitals [σC-H → σC-X*], this general stratagem has been used in conjunction with an array of secondary noncovalent interactions to achieve acyclic conformational control (ACC) in structures of interest. These secondary effects range from 1,3-allylic strain (A1,3) through to electrostatic charge-dipole and cation-π interactions. Synergy between these interactions ensures that rotation about strategic C(sp3)-C(sp3) bonds is subject to the stereoelectronic requirement for antiperiplanarity (180°). Logically, in a generic [X-CH2-CH2-Y] system (X, Y = electron withdrawing groups) conformations in which the two C(sp3)-X bonds are synclinal (i.e., gauche) are significantly populated. As such, simple donor-acceptor models are didactically and predictively powerful in achieving topological preorganization. In the case of the gauche effect, the low steric demand of fluorine ensures that the remaining substituents at the C(sp3) hybridized center are placed in a predictable area of molecular space: An exit vector analogy is thus appropriate. Furthermore, the intrinsic chemical stability of the C-F bond is advantageous, thus it may be considered as an inert conformational steering group: This juxtaposition of size and electronegativity renders fluorinated organic molecules unique among the organo-halogen series. Cognizant that the replacement of one fluorine atom in the difluoroethylene motif by another electron withdrawing group preserves the gauche conformation, it was reasoned that β-fluoroamines would be intriguing candidates for investigation. The burgeoning field of Lewis base catalysis, particularly via iminium ion activation, provided a timely platform from which to explore a postulated fluorine-iminium ion gauche effect. Necessarily, activation of this stereoelectronic effect requires a process of intramolecularization to generate the electron deficient neighboring group: Examples include protonation, condensation to generate iminium salts, or acylation. This process, akin to substrate binding, has obvious parallels with enzymatic catalysis, since it perturbs the conformational dynamics of the system [ synclinal-endo, antiperiplanar, synclinal-exo]. This Account details the development of conformationally predictable small molecules based on the [X-Cα-Cβ-F] motif through a logical process of molecular design and illustrates their synthetic value in enantioselective catalysis.
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Affiliation(s)
- Marialuisa Aufiero
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Ryan Gilmour
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
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31
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Unzue A, Cribiú R, Hoffman MM, Knehans T, Lafleur K, Caflisch A, Nevado C. Iriomoteolides: novel chemical tools to study actin dynamics. Chem Sci 2018; 9:3793-3802. [PMID: 29780512 PMCID: PMC5939837 DOI: 10.1039/c7sc04286h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 03/10/2018] [Indexed: 01/25/2023] Open
Abstract
Despite its promising biological profile, the cellular targets of iriomoteolide-3a, a novel 15-membered macrolide isolated from Amphidinium sp., have remained unknown. A small library of non-natural iriomoteolide-3a analogues is presented here as a result of a novel, highly convergent, catalysis-based scaffold-diversification campaign, which revealed the suitable sites for chemical editing in the original core. We provide compelling experimental evidence for actin as one of iriomoteolides' primary cellular targets, establishing the ability of these secondary metabolites to inhibit cell migration, induce severe morphological changes in cells and cause a reversible cytoplasmic retraction and reduction of F-actin fibers in a time and dose dependent manner. These results are interpreted in light of the ability of iriomoteolides to stabilize F-actin filaments. Molecular dynamics simulations provide evidence for iriomoteolide-3a binding to the barbed end of G-actin. These results showcase iriomoteolides as novel and easily tunable chemical probes for the in vitro study of actin dynamics in the context of cell motility processes including cell invasion and division.
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Affiliation(s)
- A Unzue
- Department of Chemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
| | - R Cribiú
- Department of Chemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
| | - M M Hoffman
- Department of Chemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
| | - T Knehans
- Department of Biochemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
| | - K Lafleur
- Department of Chemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
| | - A Caflisch
- Department of Biochemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
| | - C Nevado
- Department of Chemistry , University of Zürich , Winterthurerstrasse 190 , CH-8057 , Zürich , Switzerland .
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32
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Pitta BR, Steward OW, Fleming FF. Electrophile-Dependent Alkylations of Lithiated 4-Alkoxyalk-4-enenitriles. J Org Chem 2018; 83:2753-2762. [PMID: 29432696 DOI: 10.1021/acs.joc.7b03205] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alkylations of acyclic, lithiated 4-alkoxyalk-4-enenitriles are highly diastereoselective with an unusual electrophile-dependent preference. Alkyl halides, sulfur, chlorine, and acyl cyanide electrophiles intercept a series of lithiated 4-alkoxyalk-4-enenitriles to install contiguous tertiary-quaternary stereocenters with high diastereoselectivity, whereas acylations with ester and carbonate electrophiles are modestly selective. The diastereoselectivity is consistent with electrophilic attack on the most accessible face of the lithated nitrile for most electrophiles except ester and carbonate electrophiles, which likely precoordinate the lithiated nitrile before acylation. Intercepting the lithiated 4-alkoxyalk-4-enenitriles with a range of electrophiles provide insight into the criteria for otherwise challenging diastereoselective alkylations and acylations of acyclic nitriles.
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Affiliation(s)
| | - Omar W Steward
- Department of Chemistry and Biochemistry, Duquesne University , Pittsburgh, Pennsylvania 15282, United States
| | - Fraser F Fleming
- Department of Chemistry, Drexel University , Philadelphia, Pennsylvania 19104, United States
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33
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Boshkow J, Fischer S, Bailey AM, Wolfrum S, Carreira EM. Stereochemistry and biological activity of chlorinated lipids: a study of danicalipin A and selected diastereomers. Chem Sci 2017; 8:6904-6910. [PMID: 29147515 PMCID: PMC5632803 DOI: 10.1039/c7sc03124f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 08/07/2017] [Indexed: 11/21/2022] Open
Abstract
The syntheses of (+)-16-epi- and (+)-11,15-di-epi-danicalipin A (2 and 3) are reported. The conformations of the parent diols 5 and 6 as well as the corresponding disulfates 2 and 3 were determined on the basis of J-based configuration analysis and supported by calculations. The impact of configuration on membrane permeability in Gram-negative bacteria and mammalian cell lines was assessed as well as cytotoxicity. Although diastereomer 2 showed similar behavior to natural (+)-danicalipin A (1), strikingly, the more flexible C11,C15-epimer 3 had no effect on permeability and proved equally or more toxic towards multiple cell lines.
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Affiliation(s)
- J Boshkow
- Laboratorium für Organische Chemie , ETH Zürich , HCI H335, Vladimir-Prelog-Weg 3 , 8093 Zürich , Switzerland .
| | - S Fischer
- Laboratorium für Organische Chemie , ETH Zürich , HCI H335, Vladimir-Prelog-Weg 3 , 8093 Zürich , Switzerland .
| | - A M Bailey
- Laboratorium für Organische Chemie , ETH Zürich , HCI H335, Vladimir-Prelog-Weg 3 , 8093 Zürich , Switzerland .
| | - S Wolfrum
- Laboratorium für Organische Chemie , ETH Zürich , HCI H335, Vladimir-Prelog-Weg 3 , 8093 Zürich , Switzerland .
| | - E M Carreira
- Laboratorium für Organische Chemie , ETH Zürich , HCI H335, Vladimir-Prelog-Weg 3 , 8093 Zürich , Switzerland .
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34
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Rutledge KM, Hamlin TA, Baldisseri DM, Bickelhaupt FM, Peczuh MW. Macrocycles All Aflutter: Substitution at an Allylic Center Reveals the Conformational Dynamics of [13]‐Macrodilactones. Chem Asian J 2017; 12:2623-2633. [DOI: 10.1002/asia.201700997] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 08/04/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Kelli M. Rutledge
- Department of Chemistry University of Connecticut 55 N. Eagleville Road U-3060 Storrs CT 06269 USA
| | - Trevor A. Hamlin
- Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling Vrije Universiteit Amsterdam, NL- 1081 HV Amsterdam The Netherlands
| | - Donna M. Baldisseri
- Bruker BioSpin Corporation 15 Fortune Drive, Manning Park Billerica MA 01821 USA
| | - F. Matthias Bickelhaupt
- Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling Vrije Universiteit Amsterdam, NL- 1081 HV Amsterdam The Netherlands
- Institute of Molecules and Materials Radboud University 6525 AJ Nijmegen The Netherlands
| | - Mark W. Peczuh
- Department of Chemistry University of Connecticut 55 N. Eagleville Road U-3060 Storrs CT 06269 USA
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35
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Banik SM, Mennie KM, Jacobsen EN. Catalytic 1,3-Difunctionalization via Oxidative C-C Bond Activation. J Am Chem Soc 2017; 139:9152-9155. [PMID: 28622723 PMCID: PMC5671765 DOI: 10.1021/jacs.7b05160] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Electronegative substituents arrayed in 1,3-relationships along saturated carbon frameworks can exert strong influence over molecular conformation due to dipole minimization effects. Simple and general methods for incorporation of such functional group relationships could thus provide a valuable tool for modulating molecular shape. Here, we describe a general strategy for the 1,3-oxidation of cyclopropanes using aryl iodine(I-III) catalysis, with emphasis on 1,3-difluorination reactions. These reactions make use of practical, commercially available reagents and can engage a variety of substituted cyclopropane substrates. Analysis of crystal and solution structures of several of the products reveal the consistent effect of 1,3-difluorides in dictating molecular conformation. The generality of the 1,3-oxidation strategy is demonstrated through the catalytic oxidative ring-opening of cyclopropanes for the synthesis of 1,3-fluoroacetoxylated products, 1,3-diols, 1,3-amino alcohols, and 1,3-diamines.
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Affiliation(s)
| | | | - Eric N. Jacobsen
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138 USA
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36
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Scheidt F, Selter P, Santschi N, Holland MC, Dudenko DV, Daniliuc C, Mück-Lichtenfeld C, Hansen MR, Gilmour R. Emulating Natural Product Conformation by Cooperative, Non-Covalent Fluorine Interactions. Chemistry 2016; 23:6142-6149. [PMID: 27788283 DOI: 10.1002/chem.201604632] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Indexed: 01/22/2023]
Abstract
Pervasive in Nature, the propane unit is an essential component of numerous bioactive molecules. These range from acyclic systems, such as the neurotransmitter γ-aminobutyric acid, through to the bicyclic nuclei of various chromanes and dihydrobenzofurans. In the latter case, cyclisation via cyclic ether formation ensures a highly pre-organised structure, whilst linear scaffolds display more dynamic conformational behaviour resulting from rotation about the two internal C(sp3 )-C(sp3 ) bonds. In this study, the replacement of -[CH2 ]- units by -[CHF]- centres is evaluated as a strategy to achieve acyclic conformational control by hindering these internal rotations. Reinforcing, non-covalent fluorine interactions are validated as powerful design features that result in programmable conformational behaviours: These are encoded by the relative configuration of each centre. By exploiting cooperative neighbouring stereoelectronic effects in a multi-vicinal fluoroalkane it is possible to emulate the overall conformation of the dihydrobenzofuran scaffold found in a variety of natural products with an acyclic mimic. This is described as a function of two bond vectors at the chain termini and validated by combined theoretical, crystallographic and spectroscopic analyses. In view of the favourable physicochemical properties associated with fluorine introduction, this approach to bioactive scaffold design may prove to be expansive.
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Affiliation(s)
- Felix Scheidt
- Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Philipp Selter
- Institute for Physical Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Nico Santschi
- Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Mareike C Holland
- Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Dmytro V Dudenko
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000, Mons, Belgium
| | - Constantin Daniliuc
- Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Christian Mück-Lichtenfeld
- Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Michael Ryan Hansen
- Institute for Physical Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany
| | - Ryan Gilmour
- Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Germany.,Excellence Cluster EXC 1003, Cells in Motion, Westfälische Wilhelms-Universität Münster, Münster, Germany
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37
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Tabata H, Yoneda T, Tasaka T, Ito S, Oshitari T, Takahashi H, Natsugari H. Stereochemistry of N-Benzoyl-5-substituted-1-benzazepines Revisited: Synthesis of the Conformationally Biased Derivatives and Revision of the Reported Structure. J Org Chem 2016; 81:3136-48. [DOI: 10.1021/acs.joc.5b02900] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hidetsugu Tabata
- Faculty
of Pharma Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
| | - Tetsuya Yoneda
- Faculty
of Pharma Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
| | - Tomohiko Tasaka
- Affinity Science Corporation, 1-11-1 Nishigotanda, Shinagawa-ku, Tokyo 141-0031, Japan
| | - Shigekazu Ito
- Department
of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8552, Japan
| | - Tetsuta Oshitari
- Faculty
of Pharma Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
| | - Hideyo Takahashi
- Faculty
of Pharma Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
| | - Hideaki Natsugari
- Faculty
of Pharma Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan
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38
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Measurement, Interpretation and Use of Free Ligand Solution Conformations in Drug Discovery. PROGRESS IN MEDICINAL CHEMISTRY 2016; 55:45-147. [DOI: 10.1016/bs.pmch.2015.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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39
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Affiliation(s)
- Sundus Erbas-Cakmak
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - David A. Leigh
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Charlie T. McTernan
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Alina
L. Nussbaumer
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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40
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Larsen EM, Wilson MR, Taylor RE. Conformation-activity relationships of polyketide natural products. Nat Prod Rep 2015; 32:1183-206. [PMID: 25974024 PMCID: PMC4443481 DOI: 10.1039/c5np00014a] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Polyketides represent an important class of secondary metabolites that interact with biological targets connected to a variety of disease-associated pathways. Remarkably, nature's assembly lines, polyketide synthases, manufacture these privileged structures through a combinatorial mixture of just a few structural units. This review highlights the role of these structural elements in shaping a polyketide's conformational preferences, the use of computer-based molecular modeling and solution NMR studies in the identification of low-energy conformers, and the importance of conformational analogues in probing the bound conformation. In particular, this review covers several examples wherein conformational analysis complements classic structure-activity relationships in the design of biologically active natural product analogues.
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Affiliation(s)
- Erik M Larsen
- University of Notre Dame, Department of Chemistry & Biochemistry, 250 Nieuwland Science Hall, Notre Dame, Indiana, USA.
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41
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Discodermolide. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/b978-0-08-100023-6.00003-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
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42
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Burns M, Essafi S, Bame JR, Bull SP, Webster MP, Balieu S, Dale JW, Butts CP, Harvey JN, Aggarwal VK. Assembly-line synthesis of organic molecules with tailored shapes. Nature 2014; 513:183-8. [PMID: 25209797 PMCID: PMC4167605 DOI: 10.1038/nature13711] [Citation(s) in RCA: 213] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 07/23/2014] [Indexed: 12/24/2022]
Abstract
Molecular assembly lines, where molecules undergo iterative processes involving chain elongation and functional group manipulation are hallmarks of many processes found in Nature. We have sought to emulate Nature in the development of our own molecular assembly line through iterative homologations of boronic esters. Here we report a reagent (α-lithioethyl triispopropylbenzoate) which inserts into carbon-boron bonds with exceptionally high fidelity and stereocontrol. Through repeated iteration we have converted a simple boronic ester into a complex molecule (a carbon chain with ten contiguous methyl groups) with remarkably high precision over its length, its stereochemistry and therefore its shape. Different stereoisomers were targeted and it was found that they adopted different shapes (helical/linear) according to their stereochemistry. This work should now enable scientists to rationally design and create molecules with predictable shape, which could have an impact in all areas of molecular sciences where bespoke molecules are required.
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Affiliation(s)
- Matthew Burns
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Stéphanie Essafi
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Jessica R Bame
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Stephanie P Bull
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Matthew P Webster
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Sébastien Balieu
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - James W Dale
- Novartis Horsham Research Centre, Wimblehurst Road, Horsham, West Sussex RH13 5AB, UK
| | - Craig P Butts
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Jeremy N Harvey
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Varinder K Aggarwal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
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43
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Garduño-Castro MH, Hernández-Rodríguez M. Application of acyclic chiral auxiliaries on alkylation reactions. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2013.10.148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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44
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Allais C, Tsai AS, Nuhant P, Roush WR. Generation of stereochemically defined tetrasubstituted enolborinates by 1,4-hydroboration of α,β-unsaturated morpholine carboxamides with (diisopinocampheyl)borane. Angew Chem Int Ed Engl 2013; 52:12888-12891. [PMID: 24281884 PMCID: PMC3910328 DOI: 10.1002/anie.201307302] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 09/15/2013] [Indexed: 11/10/2022]
Abstract
On all fours: The title reaction with (Ipc)2 BH provides tetrasubstituted enolborinates which undergo aldol reactions with aldehydes to form products with all-carbon quaternary centers with exceptional diastereo- and enantioselectivity. A change to the substitution pattern of the starting amide leads to either diastereomer of the α-methyl-α-ethyl-β-hydroxy carboxamide (1 or 2).
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Affiliation(s)
- Christophe Allais
- Department of Chemistry The Scripps Research Institute 130 Scripps Way,
3A2, Jupiter FL 33458 (USA)
| | - Andy S. Tsai
- Department of Chemistry The Scripps Research Institute 130 Scripps Way,
3A2, Jupiter FL 33458 (USA)
| | - Philippe Nuhant
- Department of Chemistry The Scripps Research Institute 130 Scripps Way,
3A2, Jupiter FL 33458 (USA)
| | - William R. Roush
- Department of Chemistry The Scripps Research Institute 130 Scripps Way,
3A2, Jupiter FL 33458 (USA)
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45
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Allais C, Tsai AS, Nuhant P, Roush WR. Generation of Stereochemically Defined Tetrasubstituted Enolborinates by 1,4-Hydroboration of α,β-Unsaturated Morpholine Carboxamides with (Diisopinocampheyl)borane. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201307302] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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46
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Chen M, Roush WR. Crotylboron-based synthesis of the polypropionate units of chaxamycins A/D, salinisporamycin, and rifamycin S. J Org Chem 2013; 78:3-8. [PMID: 22703288 PMCID: PMC3465507 DOI: 10.1021/jo3008226] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Syntheses of the C(15)-C(27) fragments of chaxamycins A/D, rifamycin S, and the C(12)-C(24) fragment of salinisporamycin have been accomplished in 10 steps from commercially available starting materials. Three crotylboron reagents were utilized to construct the seven contiguous stereocenters in these fragments with excellent stereoselectivity.
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Affiliation(s)
- Ming Chen
- Department of Chemistry, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458
| | - William R. Roush
- Department of Chemistry, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458
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47
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Mycka RJ, Eckenhoff WT, Steward OW, Barefoot NZ, Fleming FF. γ- and δ-Hydroxynitriles: diastereoselective electrophile-dependent alkylations. Tetrahedron 2013. [DOI: 10.1016/j.tet.2012.10.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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48
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49
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Aquino C, Sarkar M, Chalmers MJ, Mendes K, Kodadek T, Micalizio GC. A biomimetic polyketide-inspired approach to small-molecule ligand discovery. Nat Chem 2011; 4:99-104. [PMID: 22270625 PMCID: PMC3266625 DOI: 10.1038/nchem.1200] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/14/2011] [Indexed: 02/06/2023]
Abstract
The discovery of new compounds for the pharmacological manipulation of protein function often embraces the screening of compound collections, and it is widely recognized that natural products offer beneficial characteristics as protein ligands. Much effort has therefore been focused on “natural product-like” libraries, yet the synthesis and screening of such libraries is often limited by one or more of the following: modest library sizes and structural diversity, conformational heterogeneity, and the costs associated with the substantial infrastructure of modern high-throughput screening centers. Here, we describe the design and execution of an approach to this broad problem by merging principles associated biologically-inspired oligomerization and the structure of polyketide-derived natural products. A novel class of chiral and conformationally-constrained oligomers is described (termed “chiral oligomers of pentenoic amides” – COPAs) that offers compatibility with split-and-pool methods and can be screened en masse in a batch mode. We demonstrate that a COPA library containing 160,000 compounds is a useful source of novel protein ligands by identifying a non-covalent synthetic ligand to the DNA-binding domain of the p53 transcription factor.
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Affiliation(s)
- Claudio Aquino
- Department of Chemistry, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458, USA
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50
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Steinberg A, Froimowitz M, Parrish DA, Deschamps JR, Glaser R. Solution- and solid-state conformations of C(α)-alkyl analogues of methylphenidate (Ritalin) salts: avoidance of gauche(+)gauche(-) interactions. J Org Chem 2011; 76:9239-45. [PMID: 21973080 DOI: 10.1021/jo201415h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alkyl analogues of methylphenidate (Ritalin) salts are slow onset, long duration dopamine reuptake inhibitors with a potential use as a cocaine abuse pharmacotherapy. X-ray crystallographic studies and nuclear magnetic resonance (NMR) investigations strongly suggest that avoidance of sterically unfavorable gauche(-)gauche(+) orientations effectively influences both the C(α)-alkyl side chain conformation and the formation of a predominant rotamer about the CH-CH bond ligating piperidine and C(Ar)R moieties. The favored CH-CH rotamer in D(2)O and in CD(2)Cl(2) of the pharmacologically interesting i-Bu and CH(2)-cyc-Pnt (RS,RS)-salts has the same antiperiplanar arrangement that was found in the crystal structures, although there clearly is a fast equilibrium involving smaller amounts of synclinal partners. While the rotamer in the (RS,SR)-i-Bu HCl crystal structure exhibits a synclinal orientation for the vicinal pair of adjacent methine protons, the weighted time-averaged arrangement for these protons becomes almost completely antiperiplanar when the crystals are dissolved in D(2)O. Increased steric congestion around the CH-CH bond in the analogous N-methyl tertiary ammonium salts seems to augment the quantity of the preferred rotamer within the mixture. The stereochemistry of the species observed via NMR seems to arise from specific combinations of N-methyl orientation and avoidance of sterically unfavorable gauche(-)gauche(+) arrangements.
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Affiliation(s)
- Avital Steinberg
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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