Stereoselective Synthesis of (E)-Mannosylidene Derivatives Using the Wittig Reaction

Stabilized ylides Bu3PCH(EWG), where EWG is an ester or nitrile group, react with 2,3,4,6-tetra-O-benzylmannono-1,5-lactone giving high yields of mannosylidene derivatives; in contrast to the glucose and galactose analogues, the (E)-mannosylidenes are predominant (E:Z > 9:1), thus minimizing dip...

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Bibliographic Details
Published in:Journal of organic chemistry 2006-09, Vol.71 (20), p.7888-7891
Main Authors: Coumbarides, Gregory S, Motevalli, Majid, Muse, Warda A, Wyatt, Peter B
Format: Article
Language:English
Subjects:
Carbohydrates with 4, 5, 6, ... C atoms, dissacharides and oligosaccharides
Carbohydrates. Nucleosides and nucleotides
Chemistry
Crystallography, X-Ray
Exact sciences and technology
Heterocyclic compounds
Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives
Lactones - chemistry
Magnetic Resonance Spectroscopy
Mannose - analogs & derivatives
Mannose - chemical synthesis
Molecular Conformation
Organic chemistry
Preparations and properties
Solutions
Stereoisomerism
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Summary:Stabilized ylides Bu3PCH(EWG), where EWG is an ester or nitrile group, react with 2,3,4,6-tetra-O-benzylmannono-1,5-lactone giving high yields of mannosylidene derivatives; in contrast to the glucose and galactose analogues, the (E)-mannosylidenes are predominant (E:Z > 9:1), thus minimizing dipole−dipole repulsions in the Wittig reactions. NMR indicates chair-like conformations for solutions of the (E)-mannopyranosylidenes, but not for those (Z)-isomers where data are available (EWG = CN or CO2Et). X-ray crystallography shows an approximately twist-boat conformation for the tetra-O-benzyl-protected (Z)-mannosylideneacetonitrile.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo061178s