The adduct 3-β-D-ribofuranosyl-3, 7, 8, 9-tetrahydropyrimido [1, 2-i] purin-8-ol (2), obtained from adenosine and epichlorohydrin, underwent ring fission at basic conditions. The initial ring-opening took place at C2 of the pyrimidine unit resulting in 2-(5-amino-1-β-D- ribofuranosyl-imidazol-4-yl)-1, 4, 5, 6-tetrahydropyrimidin-5-ol (3). Also the tetrahydropyrimidine ring of 3 could be opened resulting in 5-amino-1-(β-D-ribofuranosyl)- ...