Stereoselective synthesis of (E)-mannosylidene derivatives using the Wittig reaction

被引:13
|
作者
Coumbarides, Gregory S. [1 ]
Motevalli, Majid [1 ]
Muse, Warda A. [1 ]
Wyatt, Peter B. [1 ]
机构
[1] Univ London Queen Mary Coll, Sch Biol & Chem Sci, London E1 4NS, England
来源
JOURNAL OF ORGANIC CHEMISTRY | 2006年 / 71卷 / 20期
关键词
D O I
10.1021/jo061178s
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
(Chemical Equation Presented) 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. © 2006 American Chemical Society.
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页码:7888 / 7891
页数:4
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