Abstract
1, 2 : 3, 4-Di-O-isopropylidene-α-D-galacto-hexodialdo-1, 5-pyranose (4) was treated with sodium cyanide in aqueous methanol and the resulting cyanohydrin mixture (5a and 6a) was tosylated to give 1, 2 : 3, 4-di-O-isopropylidene-6-O-tosyl-L-glycero-(5b) and-D-glycero-α-D-galacto-heptopyranurononitrile (6b). Lithium aluminum hydride reduction of these tosylates 5b and 6b, followed by acetylation yielded D-glycero-N-acetylepimine (7a) and L-glycero-N-acetylepimine (8), respectively. The D-glycero-epimer (7a) thereby obtained was treated in warm acetic acid and gave a 6-acetamido-7-O-acetate (17a) exclusively, whose deacetylation with sodium methoxide yielded a 7-deacetyl derivative (19). Pfitzner-Moffatt oxidation of 19, followed by treatment of the resulting 7-oxo derivative (20) with methylmagnesium bromide gave 6-acetamido-6, 8-dideoxy-1, 2 : 3, 4-di-O-isopropylidene-L-threo-α-D-galacto-octopyranose (26). The latter (26) was converted into its D-erythro-derivative (24) by oxidation with chromium trioxide in pyridine and successive reduction with sodium borohydride. Hydrolysis of 24 with aqueous acetic acid or Amberlite IR-120 (H+) gave the N-acetate of lincosamine which constitutes a sugar component of antibacterial antibiotic, lincomycin.
