Thiosugars. XIII. An Attempt at Thiosugar Synthesis having a Vicinal cis-Dimercapto Group in the Pyranose Ring

抄録

Methyl 2, 3-dideoxy-2, 3-dimercapto-α-D-mannopyranoside, isolated as sirupy tetraacetate (XIII), was synthesized in 13% yield by reduction of methyl 2, 3-dithio-4, 6-O-benzylidene-α-D-mannopyranoside 2, 3-S-carbonate (IX) with sodium in liquid ammonia. The product was also obtainable in the same yield by alkaline treatment of methyl 2, 3-dithio-4, 6-di-O-acetyl-α-D-mannopyranoside 2, 3-S-carbonate (XII). Dithiocarbonate (IX), a key intermediate of the synthesis was obtained by the following route : epoxide opening in methyl 2, 3-anhydro-4, 6-O-benzylidene-α-D-allopyranoside (II) with sodium N, N-dimethyldithiocarbamate (I) to give methyl 2-deoxy-2 (N, N-dimethyl dithiocarbamoyl)-4, 6-O-benzylidene-α-D-altropyranoside (III), sulfonation of III, and successive intramolecular ring formation in the pyranose ring involving trans-diaxial elimination by treatment of the sulfonate (VII or VIII) with potassium acetate.