Higher-carbon sugars. Part 1. The synthesis of some octose sugars via the osmylation of unsaturated precursors
The stereochemical outcome of the osmium tetraoxide oxidation of a number of unsaturated carbohydrate derivatives, including (E)- and (Z)-6,7-dideoxy-1,2 : 3,4-di-O-isopropylidene-α-D-galacto-oct-6-enopyranose (6) and (9), methyl (Z)-6,7-dideoxy-1,2 : 3,4-di-O-isopropylidene-α-D-galacto-oct-6-enopyranuronate (8), and 7,8-dideoxy-1,2 : 3,4-di-O-isopropylidene-α-D-glycero-D-galacto-oct-7-enopyranose (10), has been examined. Such oxidations resulted in the preparation of the synthetically useful octose derivatives 1,2 : 3,4-di-O-isopropylidene-α-D-erythro-D-galacto-octopyranose (18) and 1,2 : 3,4 : 6,7-tri-O-isopropylidene-β-L-erythro-D-galacto-octopyranose (31), as well as syntheses of L-threo-D-galacto-octitol (14), D-erythro-D-galacto-octitol (21), L-erythro-D-galacto-octitol (29), and D-threo-D-galacto-octitol (35).