THE STEREOSELECTIVE SYNTHESIS OF NOVEL 4-OCTULOSE DERIVATIVES

Dihydroxylation of methyl -isopropylidene-L-xylo-oct-2-ene-4-ulofurano sonate (1) with osmium tetraoxide took place with high diastereoselect ivity to give a 7:1 mixture of methyl 6,8-di-O-isopropylidene-alpha-L- glycero-D-galacto- (2) and -D-ido-oct-4-ulofuranosonate (3). When 1 wa s dihydroxylated in the presence of dihydroquinine and dihydroquinidin e p-chlorobenzoate, an appreciable increase and decrease, respectively , in the 2/3 ratio was observed. Compound 2 was transformed into its 2 ,3-di-O-methyl derivative 4 which was deisopropylidenated to methyl yl -alpha-L-glycero-D-galacto-oct-4-ulopyranosonate (5) and subsequently degraded to dimethyl 2,3-di-O-methyl-(+)-L-tartrate (6). On the other hand, compounds 2 and 3, separately, were isopropylidenated to the cor responding 2,3:4,5:6,8-tri-O-isopropylidene derivatives 7 and 8, which were reduced with LiAlH4 to the related ,8-tri-O-isopropylidene-alpha -L-glycero-D-galacto- (9) and -D-ido-oct-4-ulofuranose (10). Finally, compounds 9 and 10 were deisopropylidenated to the corresponding L-gly cero-D-galacto- (11) and L-glycero-D-ido-oct-4-ulose (12). (C) 1998 El sevier Science Ltd. All rights reserved.