From D-glucose to enantiomerically pure cycloctanoses. the glycosidase inhibitory capacity of medium-ring carbasugars

Exhaustive dihydroxylation of the pair of cyclooctadienols consisting of 4 and 5, which are available in enantiomerically pure form from D-glucose, resulted in the formation of two diastereomeric tetraols in each case. The difference in polarity of the 6/7 and 8/9 pairs facilitated their chromatographic separation. Ensuing acetylation and PMB deprotection allowed for the assignment of relative (and ultimately absolute) stereochemistry to the resulting monohydric alcohols on the basis of J _HH analysis of their ¹H NMR spectra. The highly functionalized exomefhylenecyclooctanes 14-17, which were derived by periodinane oxidation and Wittig olefination, were further elaborated by hydroboration and global deprotection. The eight members of the cyclooctanose family of carbasugars and their precursor intermediates consistently showed patterns of J _HH values in line with the contiguous stereochemical relationships. Also assayed was their specific inhibitory behavior toward glycosidases.