Synthesis of 6-C-Substituted Purine Nucleosides : α-(Aminomethylene)-9-β-D-ribofuranosylpurine-6-acetic Acid Derivatives

α-(Aminomethylene)-β-D-ribofuranosylpurine-6-acetamide (4) and the ethyl acetate (9) have been synthesized by catalytic hydrogenation of 6-cyanomethylenepurine derivatives (3 and 7). 6-Cyanomethylenepurines were obtained by substitution of 6-chloro-9-(2, 3-O-isopropylidene-β-D-ribofuranosyl)purine (1) with α-cyanoacetamide and ethyl cyanoacetate, followed by deprotection of the isopropylidene group. Substitution on 4 and 9 with benzylamine and aniline gave the corresponding N-benzyl- and N-phenyl-substituted α-(aminomethylene)-β-D-ribofuranosylpurine-6-acetamides (5) and the ethyl acetate (10), respectively.