REACTIONS OF NITRO SUGARS: I. SOME BENZYLIDENE AND ACYL DERIVATIVES OF METHYL 3-DEOXY-3-NITRO-D-HEXOPYRANOSIDES

The 4,6-O-benzylidene derivatives VII, VIII, and XVII of methyl 3-deoxy-3-nitro-β-D-mannopyranoside, -β-D-galactopyranoside, and -α-D-glucopyranoside, respectively, were prepared. Acetylation of the β-D-manno derivative (VII) led, depending upon the reaction conditions, to its 2-O-acetate (IX) and, by way of an unexpected epimerization, to the 2-O-acetate (V) of the corresponding β-D-gluco isomer. There is evidence that this epimerization proceeds through methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-β-D-erythro-hexopyranos-2-enide (VI). This nitroolefin was obtained by a Schmidt–Rutz reaction from IX (as earlier from V) and was shown to add acetic acid readily giving V. It also added ethanol producing a 2-O-ethyl glycoside (XII). Acetylation of the galacto derivative (VIII) did not afford an acetate but proceeded with dehydration yielding methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-β-D-thero-hexopyranos-2-enide (X).A number of further derivatives of methyl 3-deoxy-3-nitro-β-D-glucopyranoside were prepared, viz., the 2-O-acetyl (XI), 2-deoxy-6-O-tosyl (XIV), and 2,6-dideoxy-6-iodo (XV) derivatives.