The isothiocyanato moiety: an ideal protecting group for the stereoselective synthesis of sialic acid glycosides and subsequent diversification.

ABSTRACT: The preparation of a crystalline, peracetyl adamantanyl thiosialoside donor protected by an isothiocyanate group is described. On activation at -78?°C in the presence of typical carbohydrate acceptors, this donor gives high yields of the corresponding sialosides with exquisite ?-selectivity. The high selectivity extends to the 4-O-benzyl-protected 3-OH acceptors, which are typically less reactive and selective than galactose 3,4-diols. Treatment of the ?-sialosides with tris(trimethylsilyl)silane or allyltris(trimethylsilyl)silane results in replacement of the C5-N5 bond by a C-H or a C-C bond. The reaction of the isothiocyanate-protected sialosides with thioacids generates amides, while reaction with an amine gives a thiourea, which can be converted into a guanidine. The very high ?-selectivities observed with the new donor and the rich chemistry of the isothiocyante function considerably extend the scope for optimization at the sialoside 5-position.

SUBMITTER: Mandhapati AR 

PROVIDER: S-EPMC4300277 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature