BRANCHED-CHAIN SUGARS .16. SYNTHESIS OF NEW BRANCHED-CHAIN CYCLITOLS HAVING EPI AND ALLO CONFIGURATION AND MYO CONFIGURATION RESPECTIVELY FROM 3-O-BENZYL-5,6-DIDEOXY-5-[C-(1,3-DITHIAN-2-YL)]-6-NITRO-D-ALLOFURANOSEAND -L-TALOFURANOSE

The Michael addition of 2-lithio-l, 3-dithiane to 3-0-benzyl-5, 6-dideoxy-l, 2-0-isopropylidene-6-nitro-α-D-ribo-hex-5-enofuranose (3) gave 3-0-benzyl-5, 6-dideoxy-5-C-(l, 3-dithian-2-yl)-1, 2-0-isopropylidene-6-nitro-β-L-talo-furanose (4) and -α-D-allofuranose (5) in 59% yield (4 : 5 = 1 : 1). Intramolecular cyclization of these compounds in weak basic conditions after removal of the isopropylidene group gave branched-chain cyclitols having epi and alio configuration ( 11 and 15) from 5 and mvo configuration (7) from 4, respectively, in good yields, and the stereochemistry of cyclization was discussed. The cyclization of 3-0-benzyl-5, 6-dideoxy-l, 2-0-isopropylidene-5-C-(nitromethyl)-6-nitro-α-D-ribo-hexofuranose prepared by the addition of nitromethane to 3 was also described. © 1979, American Chemical Society. All rights reserved.