Stereoselective synthesis of (+)-5-thiosucrose and (+)-5-thioisosucrose

Abstract

(+)-5-Thiosucrose 1, a novel isosteric sulfur analog of sucrose, was synthesized stereoselectively for the first time via indirect β-D-fructofuranosidation involving selective β-D-psicofuranosidation, followed by stereo-inversion of the secondary hydroxy group at the C-3 position on the furanose ring. Glycosidation of protected 5-thio-D-glucose with a D-psicofuranosyl donor provided β-D-psicofuranosyl 5-thio-α-D-glucopyranoside and that with D-fructofuranosyl donor gave α-D-fructofuranosyl 5-thio-α-D-glucopyranoside. Two anomeric stereocenters of the glycosyl donor and acceptor were controlled correctly to provide a single disaccharide among four possible anomeric isomers in the glycosylation. Conversion of the resulting disaccharides afforded (+)-5-thiosucrose 1 and (+)-5-thioisosucrose 2 in excellent yields, respectively. Inhibitory activities of 1 and 2 against α-glucosidase in vitro were also examined.