Synthesis of 5-thio-l-altrose

Treatment of 1,2,3-tri-O-acetyl-5,6-anhydro-d-galactofuranose with thiourea gave 1,2,3-tri-O-acetyl-5,6-dideoxy-5,6-epithio-l-altrofuranose, acetolysis of which gave 1,2,3,6-tetra-O-acetyl-5-S-acetyl-5-thio-l-altrofuranose. Deacetylation of the latter gave 5-thio-l-altrose.