Glycosides from acetylated glucosyl

Glycosides and Saccharides from Acetylated Glucosyl Trichloroacetimidates... 

The synthesis of C-glycosides may be achieved by B 2-catalyzed C-C bond formation. Thus, 3-(2,3,4,6-tetra-0-acetyl-a-D-glucosyl)propionitrile (13) can be prepared from acetobromoglucose (12) by reduction with Zn in DMF in the presence of acrylonitrile and 3 mol% hydroxocobalamin hydrochloride. Similarly, the ribo-furanosyl derivative 15 can be prepared from the corresponding acetobromofur-anose 14 (Scheme 5). 

The S,6-dithio-glucosyl donor 17 was synthesized in eight conventional reaction steps from tri-O-acetyl-D-glucal and converted in six further standard steps to the cyanobacterial sulfoUpid 18. By reaction with the corresponding alcohols under Lewis acid catalysis, the 2,6-anhydro-2 thio-D-altrose derivative 19 has been converted, almost quantitatively, to alkyl glycosides 20 which on desulfuration should give easy access to alkyl 2,6-dideoxy-P-D-r/b< -hexopyranosides. ... 

The first total synthesis of simmondsin (73) a naturally occurring cyanoglucoside has been achieved from L-quebrachitoI and D-glucose. The key steps involve the deoxygenation of epoxide (74) with lithium aluminium hydride, cyanomethylation of the ketone (75) by Homer-Emmons alkenylation (with separation of Z and E isomers) and glycosidation of alcohol (76) with 2,3,4,6-tetra-O-acetyl-P-D-glucosyl trichloroacetimidate. 

A known method [221] for the preparation of C-glycosyl cyanides from tri-chloroacetimidates has been applied to the reaction of the 0-acetyl-protected O-glucosyl trichloroacetimidate [222, 223], Reaction with trimethylsilyl cyanide gave the a-glycoside, a valuable intermediate in the synthesis of carboxylic acid derivatives or other C-glycosides, in quantitative yield. 

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