An unusual reaction of 1,6-anhydroaldohexopyranose derivatives leading to glycals.

Treatment of a solution of the 2-O-(N,N-dimethylsulfamoyl) derivative 3 of the levoglucosenone-derived carbocycle 1 in liquid ammonia at -40 to -50 degrees with sodium metal gave 73% of the glycal derivative 4 instead of the expected 2-deoxy derivative (2) of 1. Under the same conditions, the 2-O-(N,N-dimethylsulfamoyl) derivatives of 1,6-anhydro-3,4-dideoxy-4-C-methyl-beta-D-ribo- and -arabino-hexopyranoses gave, after acetylation, 70% of 6-O-acetyl-1,5-anhydro-2,3,4-trideoxy-4-C-methyl-D-erythro-hex-1-enit ol. In contrast, the 2-(N,N-dimethyl-sulfamates) obtained from 1,6-anhydro-3,4-O-isopropylidene-beta-D-galacto- and -talo-pyranose gave 6-O-acetyl-1,5-anhydro-2-deoxy-3,4-O-isopropylidene-D-lyxo-hex-1-enit ol in only low yields; the oxy substituent at C-3 may interfere with the reaction leading to the glycal.