OXIDATIVE CLEAVAGE OF THE TRICYCLIC DERIVATIVES OF 9-SUBSTITUTED GUANINES

Iodine in methanol was found to be a simple and effective reagent for the removal of prop-1-ene-1.2-diyl bridge from the tricyclic derivativ es of 9-substituted guanines exemplified by Ib-ld. The transformation proceeds via cleavage of the N8-C7 bond of the tricyclic system with f ormation of N-2-[(methoxy-1-methoxycarbonyl)ethyl]guanine derivatives 2b-2d; compounds 2b-2d were isolated and their structure assigned an t he basis of H-1 and C-13 NMR spectra. Treatment of 2b-2d with ad. ammo nia resulted in parent 9-subsituted guanines 3b-3d.