1 6,7-エピイミノヘプトーズの合成及びリンコサミンに関する合成研究

抄録

1,2: 3,4-Di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranose (2), which was easily prepared from D-galactose, was treated with sodium cyanide in aqueous methanol and the resulting cyanohydrin mixture was tosylated to give 1,2: 3,4-di-O-isopropylidene-6-O-tosyl-L-glycero-(5), mp152-154°, [α]^<20>_D-46.1°, and -D-glycero-α-D-galacto-heptopyranurononitrile (6), mp145-145.5°, [α]^<20>_D-110.4°. Lithium aluminum hydride reduction of these tosylates (5 and 6), followed by acetylation, yielded D-glycero-N-acetylepimine (9), syrup of [α]^<21>_D-50.9°, and L-glycero-N-acetylepimine (10), mp95-96°, [α]^<21>_D-121.0°, respectively. The D-glycero-N-acetylepimine (9) thereby obtained was treated in warm acetic acid to give 6-acetamido-7-O-acetyl-6-deoxy-1,2: 3,4-di-O-isopropylidene-D-glycero-α-D-galacto-heptopyranose (30) as powder of [α]^<21>_D-47.9°. Deacetylation of 30 with sodium methoxide yielded a 7-deacetyl derivative (32), amorphous powder of [α]^<21>_D-41.5°. Pfitzner-Moffatt oxidation of 32, followed by treatment of the resulting 7-oxo derivative (34) with methylmagnesium bromide in ether gave 6-acetamido-6,8-dideoxy-1,2: 3,4-di-O-isopropylidene-L-threo-α-D-galacto-octopyranose (36) as a syrup. 36 was converted into its D-erythro derivative (38), mp165-166°, [α]^<21>_D-162.7°, by oxidation with chromic anhydride in pyridine and successive reduction with sodium borohydride. The latter compound (38) was identified with an N-acetyl-1,2: 3,4-di-O-isopropylidene derivative of lincosamine which constitutes a sugar component of an antibacterial antibiotic, lincomycin.