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Satyanarayana ANV, Chatterjee T. HFIP-Mediated, Highly Chemo-, Regio-, and Stereoselective Hydrofunctionalizations of Ynamides: Access to Stereodefined Alkenes Bearing Drugs and Natural Products. J Org Chem 2024; 89:12439-12451. [PMID: 39120065 DOI: 10.1021/acs.joc.4c01373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
We disclose a sustainable and versatile synthetic strategy for the highly chemo-, regio-, and stereoselective hydrofunctionalizations of ynamides, through its activation by a solvent, HFIP, to access a wide variety of stereodefined ketene N,N, N,O, N,S, and N,Se acetals in high yield at room temperature. The reaction proceeded through the formation of the reactive keteniminium ion intermediate, formed via protonation at the β-carbon of ynamide by HFIP, followed by an attack of a nucleophile (syn-addition) at the α-carbon. When ynamides are treated with only HFIP at room temperature, the HFIP addition products of ynamides are formed in a 100% atom-economic fashion; however, in the presence of a stronger N-/O-/S-/Se-based nucleophile, the corresponding syn-hydroheterofunctionalized products are formed. Notably, HFIP played multiple roles, such as a reagent, in particular, a Brønsted acid, nucleophile, as well as solvent. Interestingly, HFIP is found to be unique for this transformation. Notably, this strategy is utilized for the late-stage functionalization of several marketed drugs and natural products, and it also enables the connection of two different drugs or a drug and a natural product through chemical bonds. Significantly, HFIP was recovered after the reaction and reused for consecutive reactions.
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Affiliation(s)
- Appanapalli N V Satyanarayana
- Department of Chemistry, Birla Institute of Technology and Science, Pilani (BITS Pilani), Hyderabad Campus, Jawahar Nagar, Hyderabad, Telangana 500078, India
| | - Tanmay Chatterjee
- Department of Chemistry, Birla Institute of Technology and Science, Pilani (BITS Pilani), Hyderabad Campus, Jawahar Nagar, Hyderabad, Telangana 500078, India
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2
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Holliday H, Bone KI, Sabio R, Vyvyan JR. Enantioselective Synthesis of the Guaipyridine Alkaloid (+)- and (-)-Cananodine. ACS OMEGA 2024; 9:7904-7909. [PMID: 38405498 PMCID: PMC10882590 DOI: 10.1021/acsomega.3c07735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/11/2024] [Accepted: 01/23/2024] [Indexed: 02/27/2024]
Abstract
Synthesis of both enantiomers of guaipyridine alkaloid cananodine was achieved. The stereocenter at C8 was set through an Evans alkylation, and the seven-membered carbocycle was constructed using an intramolecular Mizoroki-Heck reaction. Hydrogenation of an exomethylene set the C5 stereocenter. The optical rotation of each enantiomer matched the literature. The synthetic scheme is amenable to analogue preparation. (+)- and (-)-Rupestine G were also prepared.
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Affiliation(s)
- Haley
M. Holliday
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
| | - Kendelyn I. Bone
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
| | - Rhemrose Sabio
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
| | - James R. Vyvyan
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
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3
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Sit MK, Cao HH, Wu YD, Yip TC, Bendel LE, Zhang W, Dai WM. Synthesis of the Macrolactone Cores of Maltepolides via a Diene-Ene Ring-Closing Metathesis Strategy. Org Lett 2023; 25:1633-1637. [PMID: 36820513 DOI: 10.1021/acs.orglett.3c00106] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Synthesis of the C19-truncated maltepolide E has been accomplished via a diene-ene ring-closing metathesis (RCM) strategy without damage to the C11-C14 alkenyl epoxy unit. Upon release of the C17-OH group, it attacked at the C14 position with double bond migration and epoxide ring opening to furnish the C19-truncated maltepolides A and B as proposed for the biosynthesis of maltepolides.
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Affiliation(s)
- Man Ki Sit
- Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), and Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR P. R. of China
| | - Hui Hui Cao
- School of Traditional Chinese Medicine, Southern Medical University, Guangzhou 510515, P. R. of China
| | - Yan-Dong Wu
- Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), and Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR P. R. of China.,College of Chemistry, Central China Normal University, Luoyu Road 152, Hongshan District, Wuhan 430079, Hubei, P. R. of China
| | - Tsz Chun Yip
- Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), and Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR P. R. of China
| | - Lars Eric Bendel
- Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), and Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR P. R. of China
| | - Wen Zhang
- Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), and Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR P. R. of China
| | - Wei-Min Dai
- Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), and Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR P. R. of China
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4
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Dissanayake GC, Ndi CN, Markley JL, Martinez JB, Hanson PR. Total Synthesis of Sanctolide A and Formal Synthesis of (2 S)-Sanctolide A. J Org Chem 2023; 88:805-817. [PMID: 36602547 DOI: 10.1021/acs.joc.2c01922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Two synthetic strategies employing phosphate tether-mediated one-pot sequential protocols for the total synthesis of the polyketide nonribosomal peptide macrolide, sanctolide A, and the formal synthesis of the (2S)-epimer of sanctolide A are reported. In this work, a phosphate tether-mediated one-pot sequential ring-closing metathesis/cross metathesis/substrate-controlled "H2"/tether removal approach was developed to accomplish the total synthesis of the natural product sanctolide A.
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Affiliation(s)
- Gihan C Dissanayake
- Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045-7582, United States
| | - Cornelius N Ndi
- Department of Chemistry, University of Kansas, 1140 Gray-Little Hall, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Jana L Markley
- Department of Chemistry, University of Kansas, 1140 Gray-Little Hall, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James B Martinez
- Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045-7582, United States
| | - Paul R Hanson
- Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045-7582, United States
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Stereochemistry of Chiral 2-Substituted Chromanes: Twist of the Dihydropyran Ring and Specific Optical Rotation. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28010439. [PMID: 36615631 PMCID: PMC9823451 DOI: 10.3390/molecules28010439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 12/27/2022] [Accepted: 12/28/2022] [Indexed: 01/06/2023]
Abstract
Chiral 2-substituted chromanes are important substructures in organic synthesis and appear in numerous natural products. Herein, the correlation between specific optical rotations (SORs) and the stereochemistry at C2 of chiral 2-substituted chromanes was investigated through data mining, quantum-chemical calculations using density functional theory (DFT), and mechanistic analyses. For 2-aliphatic (including acyloxy and alkenyl) chromanes, the P-helicity of the dihydropyran ring usually corresponds to a positive SOR; however, 2-aryl chromanes with P-helicity tend to exhibit negative SORs. 2-Carboxyl (including alkoxycarbonyl and carbonyl) chromanes often display small experimental SORs, and theoretical calculations for them are prone to error because of the fluctuating conformational distribution with computational parameters. Several typical compounds were discussed, including detailed descriptions of the asymmetric synthesis, absolute configuration (AC) assignment methods, and systematic conformational analysis. We hope this work will enrich the knowledge of the stereochemistry of chiral 2-substituted chromanes.
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Gribble GW. Naturally Occurring Organohalogen Compounds-A Comprehensive Review. PROGRESS IN THE CHEMISTRY OF ORGANIC NATURAL PRODUCTS 2023; 121:1-546. [PMID: 37488466 DOI: 10.1007/978-3-031-26629-4_1] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.
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Affiliation(s)
- Gordon W Gribble
- Department of Chemistry, Dartmouth College, Hanover, NH, 03755, USA.
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Ali R, Ahmed W, Jayant V, alvi S, Ahmed N, Ahmed A. Metathesis reactions in total‐ and natural product fragments syntheses. ASIAN J ORG CHEM 2022. [DOI: 10.1002/ajoc.202100753] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Rashid Ali
- Jamia Millia Islamia New Delhi India 110025 Department of Chemistry Jamia Nagar,New Delhi india110025 110025 New Delhi INDIA
| | - Waqar Ahmed
- Jamia Millia Islamia Central University: Jamia Millia Islamia Chemistry INDIA
| | - Vikrant Jayant
- Jamia Millia Islamia Central University: Jamia Millia Islamia Chemistry INDIA
| | - shakeel alvi
- Jamia Millia Islamia Central University: Jamia Millia Islamia Chemistry INDIA
| | - Nadeem Ahmed
- Jamia Millia Islamia Central University: Jamia Millia Islamia Chemistry INDIA
| | - Azeem Ahmed
- Jamia Millia Islamia Central University: Jamia Millia Islamia Chemistry INDIA
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Total Synthesis and Structural Reassignment of Laingolide A. Mar Drugs 2021; 19:md19050247. [PMID: 33925490 PMCID: PMC8145716 DOI: 10.3390/md19050247] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 04/24/2021] [Accepted: 04/24/2021] [Indexed: 11/24/2022] Open
Abstract
The asymmetric total synthesis of four diastereomers of laingolide A was achieved, which led to the unambiguous assignment of the stereochemistry of the natural product. The salient features of the convergent, fully stereocontrolled approach were a copper-catalysed stereospecific Kumada-type coupling, a Julia-Kocienski olefination and an RCM/alkene migration sequence to access the desired macrocyclic enamide.
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9
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Ganguly A, Javed S, Bodugam M, Dissanayake GC, Chegondi R, Hanson PR. Synthesis of the C1−C16 Polyol‐Containing Macrolactone of 13‐Desmethyl Lyngbouilloside, an Unnatural Analog of the Originally Assigned Structure of (−)‐Lyngbouilloside. Isr J Chem 2021. [DOI: 10.1002/ijch.202100019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Arghya Ganguly
- Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence KS 66045-7582 USA
- Department of Chemistry University of Kansas, 1140 Gray-Little Hall 1567 Irving Hill Road Lawrence KS 66045 USA
| | - Salim Javed
- Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence KS 66045-7582 USA
| | - Mahipal Bodugam
- Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence KS 66045-7582 USA
| | - Gihan C. Dissanayake
- Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence KS 66045-7582 USA
- Department of Chemistry University of Kansas, 1140 Gray-Little Hall 1567 Irving Hill Road Lawrence KS 66045 USA
| | - Rambabu Chegondi
- Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence KS 66045-7582 USA
| | - Paul R. Hanson
- Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence KS 66045-7582 USA
- Department of Chemistry University of Kansas, 1140 Gray-Little Hall 1567 Irving Hill Road Lawrence KS 66045 USA
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10
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Abstract
This review covers the literature published between January and December in 2018 for marine natural products (MNPs), with 717 citations (706 for the period January to December 2018) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1554 in 469 papers for 2018), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. The proportion of MNPs assigned absolute configuration over the last decade is also surveyed.
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Affiliation(s)
- Anthony R Carroll
- School of Environment and Science, Griffith University, Gold Coast, Australia. and Griffith Institute for Drug Discovery, Griffith University, Brisbane, Australia
| | - Brent R Copp
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - Rohan A Davis
- Griffith Institute for Drug Discovery, Griffith University, Brisbane, Australia and School of Environment and Science, Griffith University, Brisbane, Australia
| | - Robert A Keyzers
- Centre for Biodiscovery, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Michèle R Prinsep
- Chemistry, School of Science, University of Waikato, Hamilton, New Zealand
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Paul D, Kundu A, Saha S, Goswami RK. Total synthesis: the structural confirmation of natural products. Chem Commun (Camb) 2021; 57:3307-3322. [DOI: 10.1039/d1cc00241d] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This feature article highlights total synthesis as one of the reliable tools for the structural confirmation of natural products.
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Affiliation(s)
- Debobrata Paul
- School of Chemical Sciences
- Indian Association for the Cultivation of Science
- Kolkata 700032
- India
| | - Ashis Kundu
- School of Chemical Sciences
- Indian Association for the Cultivation of Science
- Kolkata 700032
- India
| | - Sanu Saha
- School of Chemical Sciences
- Indian Association for the Cultivation of Science
- Kolkata 700032
- India
| | - Rajib Kumar Goswami
- School of Chemical Sciences
- Indian Association for the Cultivation of Science
- Kolkata 700032
- India
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12
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Lai Y, Dai W. Modular Total Synthesis of (–)‐Palmyrolide A and (+)‐(
5
S
,
7
S
)‐Palmyrolide A via
Ring‐Closing
Metathesis and Alkene Isomerization†. CHINESE J CHEM 2020. [DOI: 10.1002/cjoc.202000458] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Yecai Lai
- Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Clear Water Bay Kowloon Hong Kong SAR China
| | - Wei‐Min Dai
- Laboratory of Advanced Catalysis and Synthesis, Department of Chemistry and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Clear Water Bay Kowloon Hong Kong SAR China
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13
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Titov AA, Kobzev MS, Borisova TN, Listratova AV, Evenko TV, Varlamov AV, Voskressensky LG. Facile Methods for the Synthesis of 8-Ylidene-1,2,3,8-tetrahydrobenzazecines. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000203] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Alexander A. Titov
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
| | - Maxim S. Kobzev
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
| | - Tatiana N. Borisova
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
| | - Anna V. Listratova
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
| | - Tatiana V. Evenko
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
| | - Alexey V. Varlamov
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
| | - Leonid G. Voskressensky
- Organic Chemistry Department; Peoples' Friendship University of Russia (RUDN University); 6 Miklukho-Maklaya St Moscow 117198 Russian Federation
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Han P, Mao ZY, Li M, Si CM, Wei BG, Lin GQ. Synthesis of Amide Enol Carbamates and Carbonates through Cu(OTf)2-Catalyzed Reactions of Ynamides with t-Butyl Carbamates/Carbonates. J Org Chem 2020; 85:4740-4752. [PMID: 32162916 DOI: 10.1021/acs.joc.9b03512] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Pan Han
- Department of Natural Medicine, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
- College of Chemistry and Chemical Engineering, China West Normal University, 1 Shida Road, Nanchong 637002, China
| | - Zhuo-Ya Mao
- Department of Natural Medicine, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
| | - Ming Li
- Department of Natural Medicine, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
| | - Chang-Mei Si
- Department of Natural Medicine, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
| | - Bang-Guo Wei
- Department of Natural Medicine, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
| | - Guo-Qiang Lin
- Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
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15
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Herndon JW. The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2018. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.213051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Lang JH, Lindel T. Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling. Beilstein J Org Chem 2019; 15:577-583. [PMID: 30873243 PMCID: PMC6404460 DOI: 10.3762/bjoc.15.53] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 02/12/2019] [Indexed: 01/22/2023] Open
Abstract
The synthesis of the polyketide section present in the potently cytotoxic marine cyclodepsipeptide jasplakinolide and related natural products, geodiamolides and seragamides, is reported. The key step is a Negishi cross coupling of (R)-(3-methoxy-2-methyl-3-oxopropyl)zinc(II) bromide and an (E)-iodoalkene that was synthesized via an aluminium ester enolate attack at (R)-propylene oxide. The overall synthesis comprises nine steps with an overall yield of 21%. It proved to be possible to liberate the free 8-hydroxynonenoic acid and to couple it with a protected tripeptide composed of L-alanine, N,O-dimethyl-D-iodotyrosine, and TIPS-protected L-threonine, which occurs as partial structure of seragamide A. The tripeptide section of seragamide A was assembled by solution-phase synthesis and an open-chain analogue of the natural product was obtained.
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Affiliation(s)
- Jan Hendrik Lang
- TU Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106 Braunschweig, Germany
| | - Thomas Lindel
- TU Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106 Braunschweig, Germany
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