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Abstract
In this contribution, we provide a comprehensive overview of acyclic twisted amides, covering the literature since 1993 (the year of the first recognized report on acyclic twisted amides) through June 2020. The review focuses on classes of acyclic twisted amides and their key structural properties, such as amide bond twist and nitrogen pyramidalization, which are primarily responsible for disrupting nN to π*C═O conjugation. Through discussing acyclic twisted amides in comparison with the classic bridged lactams and conformationally restricted cyclic fused amides, the reader is provided with an overview of amidic distortion that results in novel conformational features of acyclic amides that can be exploited in various fields of chemistry ranging from organic synthesis and polymers to biochemistry and structural chemistry and the current position of acyclic twisted amides in modern chemistry.
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Affiliation(s)
- Guangrong Meng
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Jin Zhang
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
- College of Chemistry and Chemical Engineering, Key Laboratory of Chemical Additives for China National Light Industry, Shaanxi University of Science and Technology, Xi'an 710021, China
| | - Michal Szostak
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
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Amador AG, Watts A, Neitzel AE, Hillmyer MA. Entropically Driven Macrolide Polymerizations for the Synthesis of Aliphatic Polyester Copolymers Using Titanium Isopropoxide. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b00065] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Adrian G. Amador
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Annabelle Watts
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Angelika E. Neitzel
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Marc A. Hillmyer
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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Sharma S, Brahmachari G, Kumar A, Misra N, Kant R, Gupta VK. Molecular Modeling, Spectroscopic Investigations, and Computational Studies of DMSO solvated 7′-amino-1′,3′-dimethyl-2,2′,4′-trioxo-1′,2′,3′,4′,4a′,8a′-tetrahydrospiro[indoline-3,5′-pyrano[2,3-d]pyrimidine]-6′-carbonitrile. J STRUCT CHEM+ 2018. [DOI: 10.1134/s0022476618010389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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4
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Sharma S, Brahmachari G, Banerjee B, Nurjamal K, Kant R, Gupta VK. Synthesis, spectroscopic characterization, and crystal structure of a novel indoline derivative. CRYSTALLOGR REP+ 2016. [DOI: 10.1134/s1063774516070117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Straub BF, Gleiter R, Meier C, Gade LH. Organometallic chemistry. Beilstein J Org Chem 2016; 12:2216-2221. [PMID: 27829930 PMCID: PMC5082459 DOI: 10.3762/bjoc.12.213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 09/29/2016] [Indexed: 11/23/2022] Open
Affiliation(s)
- Bernd F Straub
- Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
| | - Rolf Gleiter
- Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
| | - Claudia Meier
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), D-81377 München, Germany
| | - Lutz H Gade
- Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
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Sharma S, Brahmachari G, Banerjee B, Nurjamal K, Kumar A, Srivastava AK, Misra N, Pandey SK, Rajnikant, Gupta VK. Synthesis, spectroscopic characterization and crystallographic behavior of a biologically relevant novel indole-fused heterocyclic compound — Experimental and theoretical (DFT) studies. J Mol Struct 2016. [DOI: 10.1016/j.molstruc.2016.04.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sharma S, Brahmachari G, Kant R, Gupta VK. One-pot green synthesis of biologically relevant novel spiro[indolin-2-one-3,4'-pyrano[2,3-c]pyrazoles] and studies on their spectral and X-ray crystallographic behaviors. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2016; 72:335-343. [PMID: 27240765 DOI: 10.1107/s2052520616005060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 03/24/2016] [Indexed: 06/05/2023]
Abstract
Syntheses via green route and single-crystal X-ray structural investigations have been carried out for three spiro[indolin-2-one-3,4'-pyrano[2,3-c]pyrazole] derivatives, 6'-amino-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-5'-carbonitrile dimethyl sulfoxide monosolvate (5a), 6'-amino-5-fluoro-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-5'-carbonitrile dimethyl sulfoxide monosolvate (5b) and methyl 6'-amino-5-cyano-1-methyl-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-3'-carboxylate 0.25 hydrate (5c), respectively. Compounds (5a) and (5b) crystallize in the triclinic space group P\bar 1, whereas compound (5c) crystallizes in the monoclinic space group C2/c. In molecules (5a) and (5b) all the rings are practically flat, while in (5c), the heterocyclic pyran ring adopts a flattened-boat conformation. In (5a) and (5b) the cyanide group is oriented in a (-ap) conformation, while the amino group is oriented in a (+ap) conformation with a pyran ring, but in (5c) both the cyanide and amino groups are oriented in a (-ap) conformation with the pyran ring. In the crystal structure of (5a) and (5b), the molecules are linked by an elaborate system of N-H...O and N-H...N hydrogen bonds to generate a zigzag-like construct. In (5c) molecules are linked by N-H...O hydrogen bonds, thereby generating extended chains. The present communication focuses on the detailed and comparative information about spectral behaviors, single-crystal X-ray crystallographic properties and solid-state supramolecular architectures of these synthesized compounds of potential biological interests.
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Affiliation(s)
- Sakshi Sharma
- X-ray Crystallography Laboratory, Post-Graduate Department of Physics and Electronics, University of Jammu, Jammu Tawi 180 006, India
| | - Goutam Brahmachari
- Laboratory of Natural Products and Organic Synthesis, Department of Chemistry, Visva-Bharati (a Central University), Santiniketan 731 235, West Bengal, India
| | - Rajni Kant
- X-ray Crystallography Laboratory, Post-Graduate Department of Physics and Electronics, University of Jammu, Jammu Tawi 180 006, India
| | - Vivek K Gupta
- X-ray Crystallography Laboratory, Post-Graduate Department of Physics and Electronics, University of Jammu, Jammu Tawi 180 006, India
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Liniger M, VanderVelde DG, Takase MK, Shahgholi M, Stoltz BM. Total Synthesis and Characterization of 7-Hypoquinuclidonium Tetrafluoroborate and 7-Hypoquinuclidone BF3 Complex. J Am Chem Soc 2016; 138:969-74. [PMID: 26713861 DOI: 10.1021/jacs.5b11750] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Derivatives of the fully twisted bicyclic amide 7-hypoquinuclidone are synthesized using a Schmidt-Aubé reaction. Their structures were unambiguously confirmed by X-ray diffraction analysis and extensive spectroscopic characterization. Furthermore, the stability and chemical reactivity of these anti-Bredt amides are investigated. 7-Hypoquinuclidonium tetrafluoroborate is shown to decompose to a unique nitrogen bound amide-BF3 complex of 7-hypoquinuclidone under anhydrous conditions and to react instantaneously with water making it one of the most reactive amides known to date.
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Affiliation(s)
- Marc Liniger
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - David G VanderVelde
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Michael K Takase
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Mona Shahgholi
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Brian M Stoltz
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
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Szostak R, Aubé J, Szostak M. Determination of Structures and Energetics of Small- and Medium-Sized One-Carbon-Bridged Twisted Amides using ab Initio Molecular Orbital Methods: Implications for Amidic Resonance along the C–N Rotational Pathway. J Org Chem 2015; 80:7905-27. [DOI: 10.1021/acs.joc.5b00881] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Roman Szostak
- Department of Chemistry, Wroclaw University, F. Joliot-Curie 14, Wroclaw 50-383, Poland
| | - Jeffrey Aubé
- Division of Chemical
Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Michal Szostak
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
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Vystorop IV, Konovalova NP, Nelyubina YV, Chernyak AV, Sashenkova TE, Klimanova EN, Utienyshev AN, Fedorov BS, Shilov GV, Kostyanovsky RG. Cyclic hydroxamic acids derived from α-amino acids 2. Regioselective synthesis, crystal structure, and antitumor activity of spiropiperidine-imidazolidine hydroxamic acids based on glycine and dl-alanine. Russ Chem Bull 2014. [DOI: 10.1007/s11172-013-0176-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Khan SI, Knobler CB, Maverick EF. Benz[cd]indol-2(1H)-one at 298 and 100 K. Acta Crystallogr C 2012; 68:o1-6. [PMID: 22223280 DOI: 10.1107/s0108270111050281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2011] [Accepted: 11/23/2011] [Indexed: 11/11/2022] Open
Abstract
Weakly diffracting crystals of benz[cd]indol-2(1H)-one (naphtholactam), C(11)H(7)NO, were unsuitable for data collection by early photographic methods. However, a diffractometer data set collected at room temperature in 1989 was solved and refined. The peak scans were broad, and the results indicated disorder or a satellite crystal. Recent data collection (on another crystal from the same sample) with an area detector at 100 K revealed the same disorder, and made it possible to refine two different, more complete, disorder models. Both models assume an occasional 180° rotation of the nearly planar centrosymmetric cis-lactam dimer. The refinements differ, especially in the anisotropic displacement parameters for the -C(=O)-NH- portion of the molecule. Both models at 100 K give a C-N (`amide') bond distance of 1.38 Å, about 0.04 Å longer than the average distance in saturated γ-lactams in the Cambridge Structural Database. Cohesive packing interactions between molecules include opposing-dipole dimers; the packing may explain the 10:1 ratio favoring the major-occupancy molecule.
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Affiliation(s)
- Saeed I Khan
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095-1569, USA
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Hachuła B, Zerzucha P, Zubko M, Kusz J. 6-Chloro-2-oxindole: X-ray and DFT-calculated study. Acta Crystallogr C 2011; 67:o413-6. [PMID: 21979979 DOI: 10.1107/s0108270111038005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2011] [Accepted: 09/16/2011] [Indexed: 11/10/2022] Open
Abstract
The molecule of the title compound (systematic name: 6-chloroindolin-2-one), C(8)H(6)ClNO, is almost planar, with a dihedral angle of 1.13 (9)° between the planes of the constituent pyrrolidine and benzene rings. Centrosymmetric dimers are formed in the crystal structure by N-H···O hydrogen bonds, and these dimers are additionally linked by Cl···Cl and C-H···O interactions. Density functional theory (DFT) calculations at the B3LYP/6-31 G(d,p) level of theory were used to optimize the molecular structure and the geometry was best reproduced by optimization of two interacting molecules. The bond orders in the molecule, estimated using the natural bond orbitals (NBO) formalism, are consistent with the observed bond lengths. In particular, the contribution of the lone pair of electrons on the N atom to the N-C bond in the N-C=O group is revealed. The measured IR spectrum of the compound shows a red shift of the N-H stretching frequency compared with the free molecule, due to the formation of the hydrogen bonds.
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Affiliation(s)
- Barbara Hachuła
- Institute of Chemistry, University of Silesia, 14th Bankowa Street, 40-006 Katowice, Poland.
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Aubry S, Sasaki K, Eloy L, Aubert G, Retailleau P, Cresteil T, Crich D. Exploring the potential of the β-thiolactones in bioorganic chemistry. Org Biomol Chem 2011; 9:7134-43. [DOI: 10.1039/c1ob05967j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vystorop IV, Konovalova NP, Nelyubina YV, Varfolomeev VN, Fedorov BS, Sashenkova TE, Berseneva EN, Lyssenko KA, Kostyanovsky RG. Cyclic hydroxamic acids derived from α-amino acids 1. Regioselective synthesis, structure, NO-donor and antimetastatic activities of spirobicyclic hydroxamic acids derived from glycine and DL-alanine. Russ Chem Bull 2010. [DOI: 10.1007/s11172-010-0055-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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15
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Vystorop IV, Lyssenko KA, Kostyanovsky RG. 2-Phenyl-3-hydroxyimidazolidin-4-one: the regioselective synthesis, structure and enantiomerically enriched crystallization. MENDELEEV COMMUNICATIONS 2003. [DOI: 10.1070/mc2003v013n03abeh001790] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Vystorop IV, Lyssenko KA, Voznesensky VN, Lodygina VP, Kostyanovsky RG. General regioselective synthesis of 2,2-disubstituted 3-hydroxyimidazolidin-4-ones. MENDELEEV COMMUNICATIONS 2002. [DOI: 10.1070/mc2002v012n05abeh001657] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Vystorop IV, Lyssenko KA, Kostyanovsky RG. 3-Hydroxy-2,2-dimethylimidazolidin-4-one: the regioselective synthesis and chiral crystallization. MENDELEEV COMMUNICATIONS 2002. [DOI: 10.1070/mc2002v012n03abeh001603] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Pawar DM, Khalil AA, Hooks DR, Collins K, Elliott T, Stafford J, Smith L, Noe EA. E and Z Conformations of Esters, Thiol Esters, and Amides. J Am Chem Soc 1998. [DOI: 10.1021/ja9723848] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Diwakar M. Pawar
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Abdelnaser A. Khalil
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Denise R. Hooks
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Kenneth Collins
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Tijuana Elliott
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Jefforey Stafford
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Lucille Smith
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
| | - Eric A. Noe
- Contribution from the Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510
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Schröder D, Goldberg N, Zummack W, Schwarz H, Poutsma JC, Squires RR. Generation of α-acetolactone and the acetoxyl diradical •CH2COO• in the gas phase. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0168-1176(97)00150-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Self-assembly of frame structures. 10. Stereochemistry of 2,5-dioxabicyclo [2.2.1]heptane-3,6-digne. Chem Heterocycl Compd (N Y) 1995. [DOI: 10.1007/bf01168620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Greenberg A, Hsing HJ, Liebman JF. Aziridinone and 2-azetidinone and their protonated structures. An ab initio molecular orbital study making comparisons with bridgehead bicyclic lactams and acetamide. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0166-1280(94)04050-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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X-ray diffraction studies of crystalline trihalomethyl ketones (RCOCX3) reveal an unusual structural deformation about the carbonyl group. Tetrahedron Lett 1992. [DOI: 10.1016/s0040-4039(00)60847-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Electronic structure and conformational properties of the amide linkage Part 9. Geometrical and electronic structures of N-alkenyllactams as determined by PE spectroscopy and semiempirical quantum chemical calculations. J Mol Struct 1992. [DOI: 10.1016/0022-2860(92)80242-a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Valle G, Crisma M, Toniolo C, Holt EM, Tamura M, Bland J, Stammer CH. Crystallographic characterization of conformation of 1-aminocyclopropane-1-carboxylic acid residue (Ac3c) in simple derivatives and peptides. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1989; 34:56-65. [PMID: 2793309 DOI: 10.1111/j.1399-3011.1989.tb01009.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The molecular and crystal structures of the C alpha,alpha-dialkylated alpha-amino acid residue 1-aminocyclopropane-1-carboxylic acid hemihydrate (H2+-Ac3c-O-.1/2 H2O) and nine derivatives and dipeptides have been determined by X-ray diffraction. The derivatives are pBrBz-Ac3c-OH, Piv-Ac3c-OH, Z-Ac3c-OH, the alpha-and beta-forms of t-Boc-Ac3c-OH, Z-Ac3c-OMe, and the 5(4H)-oxazolone from pBrBz-Ac3c-OH; the dipeptides are H-(Ac3c)-OMe and c(Ac3c)2. The values determined for the torsion angles about the N-C alpha (phi) and C alpha-C' (psi) bonds for the single Ac3c residue of Piv-Ac3c-OH, the alpha- and beta-forms of t-Boc-Ac3-OH and Z-Ac3c-OMe, and the C-terminal Ac3c residue of H-(Ac3c)2-OMe correspond to folded conformations in the "bridge" region of the Ramachandran map. The structures of pBrBz-Ac3c-OH and Z-Ac3c-OH, however, are unusual in having a semi-extended conformation for the phi, psi angles. The N-terminal Ac3c residue of H-(Ac3c)2-OMe adopts a novel type of C5 conformation, characterized inter alia by an (amino) N. . .H-N (peptide) intramolecular hydrogen bond. While the acyl N alpha-blocking groups form trans amides (pBrBz-Ac3c-OH and Piv-Ac3c-OH), the urethane groups may adopt either the trans [Z-Ac3c-OH and t-Boc-Ac3c-OH (alpha-form)] or the cis amide conformations [t-Boc-Ac3c-OH(beta-form) and Z-Ac3c-OMe]. The five- and six-membered rings of the 5(4H)-oxazolone and the 2,5-dioxopiperazine, respectively, are planar. The four independent molecules in the asymmetric unit of the free alpha-amino acid are zwitterionic.
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Affiliation(s)
- G Valle
- Department of Organic Chemistry, University of Padova, Italy
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Valle G, Crisma M, Toniolo C, Yu KL, Johnson RL. Crystal-state structural analysis of two gamma-lactam-restricted analogs of Pro-Leu-Gly-NH2. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1989; 33:181-90. [PMID: 2565891 DOI: 10.1111/j.1399-3011.1989.tb00207.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The crystal structures of two analogs of Pro-Leu-Gly-NH2 (1), containing a gamma-lactam conformational constraint in place of the -Leu-Gly- sequences, are described. The highly biologically active (S,R)-diastereomer 2a is semi-extended at the C-terminus, with the N-terminal Pro residue in the unusual "C5" conformation [psi 1 = -0.8(15) degrees] stabilized by a (peptide)N-H...N(amino) intramolecular H-bond [the N(3)...N(4) separation is 2.687(11)A]. Conversely, the N,N'-isopropylidene aminal trihydrate of the (S,S)-diastereomer 2b, compound 3, adopts a beta-bend conformation at the C-terminus, as already reported for 1. However, the backbone torsion angles [phi 2 = 57.4(4), psi 2 = -129.9(3) degrees; psi 3 = -92.3(4), phi 3 = 6.4(5) degrees] lie close to the values expected for the corner residues of an ideal type-II' beta-bend. A weak intramolecular 4----1 H-bond is seen between the Gly carboxyamide anti-NH and Pro C = O groups. In the newly formed 2,2,3,4-tetraalkyl-5-oxo-imidazolidin-1-yl moiety the psi 1 torsion angle is 12.9(4) degrees and the intramolecular N(3)...N(4) separation is 2.321(4)A.
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Affiliation(s)
- G Valle
- Department of Organic Chemistry, University of Padova, Italy
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Sudhakar PV, Chandrasekhar J. Geometry changes induced by negative hyperconjugative interactions involving carbonyl and thiocarbonyl groups. J Mol Struct 1989. [DOI: 10.1016/0022-2860(89)80076-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Frequencies and integral intenstities of the lactone and ester carbonyls of natural guaianolides. Chem Nat Compd 1987. [DOI: 10.1007/bf00596640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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