Synthesis of guanosine 5'-(beta-L-fucopyranosyl)diphosphate revisited

It will be demonstrated that a successful synthesis of beta-L-fucopyranose-1-phosphate (2), a key intermediate in the preparation of guanosine 5'-(beta-L-fucopyranose)-diphosphate (1), strongly depends on the nature of the acyl protecting groups for the non-anomeric hydroxyl functions. Thus, the perbenzoylated, instead of peracetylated, alpha-L-fucopyranosyl trichloroacetimidate (11) or the corresponding ethyl beta-thiofucopyranoside proved to be a convenient starting compound for the preparation of 2. Further, condensation of N,N'-dicyclohexyl-4-morpholinecarboxamidinium guanosine 5'-morpholidophosphate with excess 2 gave the title compound without concomitant formation of bisguanosine-5'-diphosphate (16).