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Glycosyl chlorides, glycosides transformed

The ability to chemoselectively deprotect pent-4-enyl glycosides opens an avenue for a two-step transformation of NPGs into different glycosyl donors. In this context, NPGs can be transformed [50] into thioglycosides 81 [51,52,53], glycosyl trichloroacetimidates 82 [54], and glycosyl chlorides 83 [55] (O Scheme lie). [Pg.580]

A 2-(trimethylsilyl)ethyl glycoside is convertible into a glycosyl chloride by treatment with 1,1-dichloromethyl methyl ether in the presence of zinc(II) chloride, tin(IV) chloride, or iron(III) chloride. Normally an a-chloro sugar is the product. If a (3-chloro product is formed first (kinetic product) by participation from a 2-O-substituent, this is rapidly equilibrated into the thermodynamically more stable a product (anomeric effect, Section VI). The transformation is compatible with acetyl, benzoyl, and benzyl protecting groups and most importandy, also with the presence of inter-residue glycosidic bonds 229,230... [Pg.122]

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Glycosyl chlorides

Glycosyl glycosidation

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