SYNTHESIS OF GUANOSINE 5'-(BETA-L-FUCOPYRANOSYL)DIPHOSPHATE REVISITED

It will be demonstrated that a successful synthesis of beta-L-fucopyra nose-1-phosphate (2), a key intermediate in the preparation of guanosi ne 5'-(beta-L-fucopyranose)-diphosphate (1), strongly depends on the n ature of the acyl protecting groups for the non-anomeric hydroxyl func tions. Thus, the perbenzoylated, instead of peracetylated, alpha-L-fuc opyranosyl trichloroacetimidate (11) or the corresponding ethyl beta-t hiofucopyranoside proved to be a convenient starting compound for the preparation of 2. Further, condensation of N,N'-dicyclohexyl-4-morphol inecarboxamidinium guanosine 5'-morpholidophosphate with excess 2 gave the title compound without concomitant formation of bisguanosine-5'-d iphosphate (16).