Synthesis of 3-S-C (5-Acetamido-3.5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonic Acid)-3-thio-galactopyranose Derivatives

3-S-α-D-Neuraminyl-(2→3)-D-galactose derivatives were synthesized. As the glycosyl acceptors, 4, 6-O-ethylidene-1,2-O-isopropylidene-3-O-trifluoromethanesulfonyl-α-D-gulopyranose (6) and 1, 2-di-O-acetyl-4,6-O)-isopropylidene-3-O-trifluoromethanesulf onyl-β-D-gulopyranose (13) were prepared from 4,6-O-ethylidene-1,2-O-isopropylidene-a-o-galactopyranose (3) in several steps. Condensation of 6 or 13 with the sodium salt of methyl 5-acetamido-4,7,8, 9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-α-D-galacto-2-nonulopyranosonate (2) gave the corresponding 3-S-(N-acetyl-α-D-neuraminyl)-3-thio-D-galactose derivatives (14 and 15). Compound 15 was converted, via O-deisopropylidenation and subsequent acetylation, into the desired product (17).