2,3-(1′-Pyrazolino-3′,4′) hexopyranosides and their products of decomposition

The methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitrohex-2-enopyranosides having the β-D-erythro (1), α-D-erythro (2), β-D-threo (3), and α-D-threo (4) configurations reacted with diazomethane to give high yields of 2,3-(1′-pyrazolino-3′,4′) derivatives (5–8). The pyrazolines 5 and 6 (from 1 and 2) were deduced on the basis of nuclear magnetic resonance and optical rotatory dispersion data to possess the β- and α-D-gluco configurations, and 7 and 8 (from 3 and 4), to have the β- and α-D-ido configurations, respectively. Thermolysis of 5, 6, and 8 led to the methyl-branched, nitroolefinic glycosides 9, 10, and 11 (the 2-C-methyl derivatives of 1, 2, and 4), whereas 7 afforded the corresponding 2,3-C-methylene derivative 12, a cyclopropano sugar. The α-anomeric cyclopropano derivative 13 was obtained from 8 by decomposition on silica gel.