Purines, pyrimidines, and imidazoles. Part XLII. Stereospecific synthesis of some D-xylofuranosylimidazole derivatives from oxazoline intermediates and some related compounds derived from D-ribofuranosylamine

Abstract

The reaction of 3,5-O-isopropylidene-D-xylofuranosylamine with ethyl formimidate (or acetimidate) or derived formamidines gave 3,5-O-isopropylidene-α-D-xylofuranoso[1,2-d]-Δ^2′-oxazoline (or the 2′-methyl derivative), which with α-amino(cyano)acetamide or ethyl α-amino(cyano)acetate gave stereospecifically the corresponding 5-amino-1-(3,5-O-isopropylidene-α-D-xylofuranosyl)imidazole-4-carboxylic acid derivatives, from which the isopropylidene groups were removed by acidic hydrolysis. D-Xylopyranosylamine with dimethylformamide di-methyl acetal produced an acyclic xylopyranosylformamidine from which 5-amino-1-D-xylopyranosylimidazole-4-carboxamide was prepared, but on acidic treatment the formamidine gave the corresponding xylofuranosyl derivative. 2,3-O-Isopropylidene-D-ribofuranosylamine with dimethylformamide dimethyl acetal gave an acyclic ribosylformamidine which with ethyl α-amino(cyano)acetate produced mainly a β-D-imidazole ribofuranoside. The structures assigned were confirmed by analytical and u.v., n.m.r., and mass spectral techniques.