Synthesis of 2,4-diamino-5,6,7,8,9,10-hexahydro-5,9-methanopyrimido [4,5-b]azocine

We have initiated a program aimed at the synthesis of derivatives of 2,4-di amino-5,6,7,8,9,10-hexahydro-5, 9-methanopyrimido[4, 5-b]azocine (3) as pot ential selective inhibitors of Pneumocystis carinii DHFR. The present pap e r describes a simple synthesis of 3 from 2,4,6-triaminopyrimidine and 2-cyc lohexen-1-one as well as methodology for the introduction of a variety of s ubstituents at bridgehead position C-9.