Dimethylaminomethylene-α-D-xylo-hept-5-ulofuranurononitrile as building block in the synthesis of 'reversed' C-nucleoside analogues

Abstract

3-O-Benzyl-6-deoxy-1,2-O-isopropylidene-6-(dimethylaminomethylene) -α-D-xylo-hept-5-ulofuranurononitrile (1) was reacted with amidinium salts, S-methylisothiouronium sulfate, and guanidinium chloride, respectively, in the presence of bases to furnish the 4-(3-O-benzyl-1,2-O-isopropylidene- α-D-xylo-tetrofuranos-4-yl)pyrimidine-5-carbonitriles 2 and the 4-(1,2-O-isopropylidene-α-D-glycero-tetr-3-enofuranos-4-yl) pyrimidine-5-carbonitriles 3, respectively. Treatment of 1 with ethyl 5-aminopyrazole-4-carboxylates yielded the ethyl 7-(3-O-benzyl-1,2-O- isopropylidene-α-D-xylo-tetrofuranos-4-yl)-6-cyanopyrazolo[1,5-a] pyrimidine-3-carboxylates 4 and the ethyl 7-amino-6-(3-O-benzyl-1,2-O- isopropylidene-α-D-xylo-pentofuranuronoyl)pyrazolo[1,5-a] pyrimidine-3-carboxylates 5, respectively. Reaction of 1 with 2-benzimidazolylacetonitrile in the presence of sodium methanolate afforded 1-amino-2-(3-O-benzyl-1,2-O-isopropylidene-α-D-xylo-pentofuranuronoyl) benzo[4,5]imidazo[1,2-a]pyridine-4-carbonitrile (6) and 1-amino-2-(3-deoxy-1,2- O-isopropylidene-α-D-glycero-pent-S-enofuranuronoyl)benzo[4,5]imidazo[1, 2-a]pyridine-4-carbonitrile (7). © 2006 Verlag der Zeitschrift für Naturforschung.