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Liu H, Laporte AG, Gónzalez Pinardo D, Fernández I, Hazelard D, Compain P. An Unexpected Lewis Acid-Catalyzed Cascade during the Synthesis of the DEF-Benzoxocin Ring System of Nogalamycin and Menogaril: Mechanistic Elucidation by Intermediate Trapping Experiments and Density Functional Theory Studies. J Org Chem 2024; 89:5634-5649. [PMID: 38554093 DOI: 10.1021/acs.joc.4c00134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/01/2024]
Abstract
An unexpected Lewis acid-catalyzed carbohydrate rearrangement of a 1,5-bis-glycopyranoside to the product of a formal intramolecular C-aryl glycosylation reaction is reported. Mechanistic studies based mainly on intermediate trapping experiments and density functional theory (DFT) calculations reveal a cascade process involving three transient (a)cyclic oxocarbenium cations, the breaking of three single C(sp3)-O bonds, and the formation of three single bonds (i.e., exo-, endo-, and C-glycosidic bonds), leading to the 2,6-epoxybenzoxocine skeleton of bioactive natural glycoconjugates related to serjanione A and mimocaesalpin E. DFT calculations established that the generation of the pyran moiety embedded in the bridged benzoxocin ring system is likely to proceed through an unusual ring-closure of an ortho-quinone methide intermediate in which the attacking nucleophile is a carbonyl oxygen.
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Affiliation(s)
- Haijuan Liu
- Laboratoire d'Innovation Moléculaire et Applications (LIMA), Université de Strasbourg, Université de Haute-Alsace, CNRS (UMR 7042), Equipe de Synthèse Organique et Molécules Bioactives (SYBIO), Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67000 Strasbourg, France
| | - Adrien G Laporte
- Laboratoire d'Innovation Moléculaire et Applications (LIMA), Université de Strasbourg, Université de Haute-Alsace, CNRS (UMR 7042), Equipe de Synthèse Organique et Molécules Bioactives (SYBIO), Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67000 Strasbourg, France
| | - Daniel Gónzalez Pinardo
- Departamento de Química Orgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Israel Fernández
- Departamento de Química Orgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Damien Hazelard
- Laboratoire d'Innovation Moléculaire et Applications (LIMA), Université de Strasbourg, Université de Haute-Alsace, CNRS (UMR 7042), Equipe de Synthèse Organique et Molécules Bioactives (SYBIO), Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67000 Strasbourg, France
| | - Philippe Compain
- Laboratoire d'Innovation Moléculaire et Applications (LIMA), Université de Strasbourg, Université de Haute-Alsace, CNRS (UMR 7042), Equipe de Synthèse Organique et Molécules Bioactives (SYBIO), Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67000 Strasbourg, France
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Pero B, Peczuh MW. Synthesis of a Diacetonide-Protected, Mannose-Based Oxepine: Configurational Control of Anomeric Acetate Activation. J Org Chem 2022; 87:7474-7479. [PMID: 35576505 PMCID: PMC10116867 DOI: 10.1021/acs.joc.2c00206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Carbohydrate-based oxepines are seven-membered-ring oxacycles containing an enol ether moiety. These compounds have been used as intermediates in the preparation of septanose carbohydrates by functionalization through their double bond. Reported here is a new synthesis of a carbohydrate based oxepine that uses 2,3;4,6-di-O-acetonide mannose as a key starting material. The oxepine is an important precursor used in the synthesis of septanose glycomimetics of mannopyranosides. The central feature of the synthesis is a two-step sequence that converts a septanose 1,2-di-O-acetate to the septanosyl bromide and onward to the oxepine via a reductive elimination.
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Affiliation(s)
- Bryant Pero
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, U3060, Storrs, Connecticut 06269, United States
| | - Mark W Peczuh
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, U3060, Storrs, Connecticut 06269, United States
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Ramdular A, Woerpel KA. Diastereoselective Substitution Reactions of Acyclic β-Alkoxy Acetals via Electrostatically Stabilized Oxocarbenium Ion Intermediates. Org Lett 2022; 24:3217-3222. [PMID: 35446592 PMCID: PMC9817112 DOI: 10.1021/acs.orglett.2c01004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Substitution reactions of acyclic β-alkoxy acetals proceeded with generally high diastereoselectivities (>90:10) to form the anti product. Mechanistic experiments supplemented with computational studies suggest that, upon activation of the acetal, the resulting oxocarbenium ion is electrostatically stabilized by the β-alkoxy group. This stabilization defines the conformation of the reactive intermediate, which can be attacked preferentially from the more exposed face, leading to the observed products.
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Affiliation(s)
- Amanda Ramdular
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA)
| | - K. A. Woerpel
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA),Corresponding Author: K. A. Woerpel – Department of Chemistry, New York University, New York, New York 10003, United States;
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Pote AR, Pascual S, Planas A, Peczuh MW. Indolyl Septanoside Synthesis for In Vivo Screening of Bacterial Septanoside Hydrolases. Int J Mol Sci 2021; 22:4497. [PMID: 33925857 PMCID: PMC8123396 DOI: 10.3390/ijms22094497] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 12/29/2022] Open
Abstract
Building-up and breaking-down of carbohydrates are processes common to all forms of life. Glycoside hydrolases are a broad class of enzymes that play a central role in the cleavage of glycosidic bonds, which is fundamental to carbohydrate degradation. The large majority of substrates are five- and six-membered ring glycosides. Our interest in seven-membered ring septanose sugars has inspired the development of a way to search for septanoside hydrolase activity. Described here is a strategy for the discovery of septanoside hydrolases that uses synthetic indolyl septanosides as chromogenic substrates. Access to these tool compounds was enabled by a route where septanosyl halides act as glycosyl donors for the synthesis of the indolyl septanosides. The screening strategy leverages the known dimerization of 3-hydroxy-indoles to make colored dyes, as occurs when the β-galactosidase substrate X-Gal is hydrolyzed. Because screens in bacterial cells would enable searches in organisms that utilize heptoses or from metagenomics libraries, we also demonstrate that septanosides are capable of entering E. coli cells through the use of a BODIPY-labeled septanoside. The modularity of the indolyl septanoside synthesis should allow the screening of a variety of substrates that mimic natural structures via this general approach.
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Affiliation(s)
- Aditya R. Pote
- Department of Chemistry, University of Connecticut, 55 N. Eagleville Road U3060, Storrs, CT 06269, USA;
| | - Sergi Pascual
- Laboratory of Biochemistry, Institute Químic de Sarrià, University Ramon Llull, 08017 Barcelona, Spain;
| | - Antoni Planas
- Laboratory of Biochemistry, Institute Químic de Sarrià, University Ramon Llull, 08017 Barcelona, Spain;
| | - Mark W. Peczuh
- Department of Chemistry, University of Connecticut, 55 N. Eagleville Road U3060, Storrs, CT 06269, USA;
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