New methodology for the preparation of guanosine-type nucleoside analogues from 0- amino carbamyl nucleoside precursors has been developed and is demonstrated by the three-step, high-yield synthesis of guanosine (16) from 5-amino-l-(~-~-ribofuranosyl) imidazole-4-carboxamide (1, AICA-riboside). Treatment of 1-(alkoxycarbony1)-3- (arylmethy1) thioureas 8 with phosgene in the presence of triethylamine affords the highly ...
