(2R)- and (2S)-2,3-Epoxypropyl, (3R)- and (3S)-3,4-epoxybutyl and (4S)- 4,s-epoxypentyl B- Dglucopyranoside , together with the (3R)- and (3s)-3,4-epoxybutyl β- cellobiosides , have been prepared by condensation of a glycosyl bromide with the appropriate enantiomer of a chiral alcohol containing a diol protected as an isopropylidene acetal, and subsequent manipulation of the unmasked diol into the epoxide function. As well, in an improvement to the whole process, both diastereoisomers of the various epoxypropyl and epoxybutyl glycosides were available from just the one enantiomer of the alcohol by an alternative manipulation of the diol. Finally, precursors to 2,3-epoxy-4-hydroxybutyl β-D-glucosides and β- cellobiosides were prepared in high optical purity by Sharpless asymmetric epoxidation of the appropriate 4-hydroxybut-2-enyl glycosides.
Synthetic Applications of Chiral Unsaturated Epoxy Alcohols Prepared by Sharpless Asymmetric Epoxidation