Synthesis of derivatives of C-nucleoside analogues using 'push-pull' functionalized monosaccharides.

7-Deoxy-1,2:3,4-di-O-isopropylidene-alpha-D-galacto-heptopyranos-6-ulose (1) reacted with carbon disulphide and methyl iodide in the presence of a base to furnish 7,8-dideoxy-1,2:3,4-di-O-isopropylidene-8,8-bis(methylthio)]-alpha-D-galacto-oct-7-enopyranos-6-ulose (2). This 'push-pull' activated unsaturated monosaccharide underwent a ring closure reaction with hydrazine hydrate to give the 'inversed' C-nucleoside analogue 3. Compound 1 and malononitrile yielded the 7-cyano-6,7-dideoxy-1,2:3,4-di-O-isopropylidene-6-methyl-alpha-D-galacto-oct-6-enopyranurononitrile (4). Treatment of 4 with carbon disulphide and methyl iodide in the presence of a base afforded the sugar 'push-pull' butadiene 5 which was transformed into the pyridine nucleoside analogue 6.