PREPARATION OF HIGHER-CARBON SUGARS BY STEREOSELECTIVE OSMYLATION OF RELATED ALLYLIC ALCOHOLS

The catalytic osmylation of the following higher-carbon sugar allylic alcohols and enones was examined. 3-O-Benzyl-5-deoxy-5-C-[(E)-7-deoxy-1,2:3,4-di-O-isopropylidene-alpha-D-galacto-heptopyranos-6-ulos-7-ylidene]-1,2-O-isopropylidene-alpha-D-xylofuranose (5) afforded 93% of 3-O-benzyl-6-C-(1,2:3,4-di-O-isopropylidene-alpha-D-galacto-hexopyranos-6-ulos-6-yl)-1,2-O-isopropylidene-L-glycero-alpha-D-gluco- (10) and -D-glycero-beta-L-ido-hexofuranose (11) in the ratio 2:3. 3-O-Benzyl-5-deoxy-5-C-[(E)-7-deoxy-1,2:3,4-di-O-isopropylidene-D-glycero-alpha-D-galacto-heptopyranos-7-ylidene]-1,2-O-isopropylidene-alpha-D-xylofuranose (6) gave 75% of 3-O-benzyl-6-C-(1,2:3,4-di-O-isopropylidene-D-glycero-alpha-D-galacto-hexopyranos-6-yl)-1,2-O-isopropylidene-L-glycero-alpha-D-gluco- (12) and -D-glycero-beta-L-ido-hexofuranose (13) in the ratio 4:1. The L-glycero isomer (7) of 6 afforded 75% of 3-O-benzyl-6-C-(1,2:3,4-di-O-isopropylidene-L-glycero-alpha-D-galacto-hexopyranos-6-yl)-1,2-O-isopropylidene-L-glycero-alpha-D-gluco- (14) and -D-glycero-beta-L-ido-hexofuranose (15) in the ratio 53:47. 3-O-Benzyl-6-deoxy-1,2-O-isopropylidene-6-C-[methyl (E)-2,3,4-tri-O-benzyl-6-deoxy-alpha-D-glucopyranosid-6-ylidene]-alpha-D-xylo-hexofuranos-5-ulose (8) gave 65% of 3-O-benzyl-1,2-O-isopropylidene-6-C-[methyl 2,3,4-tri-O-benzyl-D-glycero-alpha-D-gluco-hexopyranosid-6-yl]-alpha-D-gluco- (19) and -[L-glycero-alpha-D-gluco-]-beta-L-ido-hexofuranos-5-ulose (20) in the ratio 55:45. 3-O-Benzyl-6-deoxy-1,2-O-isopropylidene-6-C-[methyl (E)-2,3,4-tri-O-benzyl-6-deoxy-alpha-D-glucopyranosid-6-ylidene]-alpha-D-glucofuranose (9) afforded 71% of 3-O-benzyl-1,2-O-isopropylidene-6-C-[methyl 2,3,4-tri-O-benzyl-D-glycero-alpha-D-gluco-hexopyranosid-6-yl]-D-glycero-alpha-D-gluco- (21) and -[L-glycero-alpha-D-gluco-]-L-glycero-alpha-D-gluco-hexofuranose (22) in the ratio 9:1. The configurations of all new compounds were assigned by X-ray, chemical, and spectral correlations. These reactions followed Kishi's rule, except that of 5 which afforded mainly the anti-Kishi product 11.