the primary hydroxyl group and oxidation, the 4'-ketonucleosides 6a-c and 7c were obtained. Reaction of compounds 6a,b, and 7c with sodium cyanide and subsequent deprotection gave the target 1-(4'-C-cyano-alpha-D-mannopyranosyl)nucleosides 12a-c. Deoxygenation at the 4'-position of cyanohydrins 8a,b, and 11c followed by deprotection led to the desired 1-(4'-C-cyano-4'-deoxy-alpha-D-talopyranosyl)nucleosides