Preparation of 9-(β-D-ribofuranosyl)-2-hydroxypurine

Reaction of 5-aminocytosine (VI) with ethyl orthoformate afforded 2-hydroxypurine (I) which on acid-catalysed fusion with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose, followed by methanolysis, gave the 1-ribofuranosyl derivative of I (II). Reaction of the mercuric salt of I with 2,3,5-tri-O-benzoyl-D-ribofuranosyl chloride in toluene in the presence of mercuric bromide, or reaction of the monosodium salt of I with 2,3,5-tri-O-benzoyl-D-ribofuranosyl bromide in acetonitrile, afforded 9-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-2-hydroxypurine (VII) which was methanolysed to 9-(β-D-ribofuranosyl)-2-hydroxypurine (III). The compound III was prepared also by deamination of 9-(β-D-ribofuranosyl)-2-aminopurine (X) with nitrous acid.