Nucleosides, 38 1) The Ribonucleosides of Allopurinol

Of the various conceivable ribonucleosides of allopurinol, the N ‐1‐, N ‐2‐, and N ‐5‐isomers (9c‐11c) as well as the 1, 5‐and 2,5‐bis‐ribosylated derivatives 6c and 7c have been prepared via stannic chloride‐induced glycosylation of bis (trimethylsilyl)allopurinol 4 with acylated ribofuranoses (5) . Trimethylsilyl triflate as catalyst in addition produced the O 4 ‐ribosylated isomer 8a . – The structures of the products were secured from UV, 1 H, and 13 C NMR data. –Their xanthine oxidase inhibitory activity was evaluated.