The synthesis and osmylation of 7,8-dideoxy-1,2:3,4-di- O-isopropylidene-β- l- glycero- d- galacto-oct-7-enopyranose and related studies

Abstract

A stereocontrolled route to 7,8-dideoxy-1,2:3,4-di- O-isopropylidene-β- l- glycero- d- galacto-oct-7-enopyranose ( 8) has been developed from 6,7-anhydro-1,2:3,4-di- O-isopropylidene-β- l- erythro- d- galacto-octopyranose ( 15), in which the final and key step involved a facile, reductive elimination on the epoxy-iodide 18. As predicted by Kishi's empirical rule, the major product obtained on catalytic osmylation of either 8 or its 6- O-benzyl derivative 21 possesses the β- l- erythro- d- galacto configuration ( i.e., 19 or 22, respectively).