A synthesis of 2-β-D-ribofuranosyl-4-selenazolecarboxamide (selenazofurin) and certain N-substituted amide derivatives suitable for large scale syntheses



A new process suitable for large scale synthesis of the antitumor-antiviral agent, 2-β-D-ribofuranosyl-4-selenazolecarboxamide (selenazofurin, 1), has been developed. Thus, 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (3) was converted with cyanotrimethylsilane and stannic chloride to the crystalline 2,5-anhydro-3,4,6-tri-O-benzoyl-β-D-allononitrile (4) without chromatography. Cyanosugar 4 in ethanol was treated with hydrogen selenide gas to afford stereospecifically the unstable 2,5-anhydro-3,4,6-tri-O-benzoyl-β-D-allonoselenoamide (5) which was converted in situ by ethyl bromopyruvate to the stable ethyl 2-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-4-selenazolecarboxylate (6). Selenazole ethyl ester 6 was deprotected with sodium methoxide affording methyl 2-β-D-ribofuranosyl-4-selenazolecarboxylate (7) which was aminated with ammonia to provide selenazofurin (1) or with other amines to provide N-substituted selenazofurin amides.