Highly stereoselective addition of organozinc reagents to pentopyranose derived glycals: effect of protecting group and assignment of C-glycoside stereochemistry

The nucleophilic addition of ethyl 3-propionylzinc iodide to a variety of differently protected pentopyranose derived d-glycals 6a– g proceeds with good to high levels of diastereoselectivity to provide the corresponding β- C-glycosides 7 . The stereochemistry of the para-nitrobenzoate derivative 7d...

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Published inTetrahedron Vol. 60; no. 23; pp. 5085 - 5092
Main Authors Cook, Matthew J, Fletcher, Matthew J.E, Gray, Diane, Lovell, Peter J, Gallagher, Timothy
Format Journal Article
LanguageEnglish
Published OXFORD Elsevier Ltd 31.05.2004
Elsevier
Subjects
C-Glycosides
Chemistry
Chemistry, Organic
Glycals
Organozinc
Physical Sciences
Science & Technology
Glycals
Organozinc
C-Glycosides
GLYCOPYRANOSIDES
CIGUATOXIN
2,3-DICHLORO-5,6-DICYANO-P-BENZOQUINONE
ACETATES
STEREOSPECIFIC SYNTHESIS
ACETYLATED GLYCALS
GLYCOSYLATION
ALLYLTRIMETHYLSILANE
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Summary:The nucleophilic addition of ethyl 3-propionylzinc iodide to a variety of differently protected pentopyranose derived d-glycals 6a– g proceeds with good to high levels of diastereoselectivity to provide the corresponding β- C-glycosides 7 . The stereochemistry of the para-nitrobenzoate derivative 7d has been confirmed by X-ray crystallography, and the stereochemistry of the other β- C-glycoside products has been correlated to 7d . The stereochemical outcome observed supports the earlier suggestion by Isobe that through-space effects are important in stabilising and controlling the reactivity of the intermediate oxonium species represented by 11 . Graphic
ISSN:0040-4020
1464-5416
DOI:10.1016/j.tet.2004.04.004