Syntheses and properties of some polymethylene-bridged adenines

Abstract

Syntheses of novel 1,2-, 2,N(6)-, and 2,9-polymethylene-bridged derivatives of adenine (7)–(9) are described. Cyclization of the intermediate 2,N(4)-bridged 4,6-diamino-5-formamidopyrimidines (6) gives a mixture of isomeric, 2,N(6)- and 2,9-bridged adenines in a ratio controlled by the number (n) of methylene groups in the chain; when n= 7, the first type (8) predominates, when n= 11, the second type (9) predominates, and when n= 9, both are formed in almost equal amounts. The structures (8) are confirmed by independent syntheses from appropriate cyclic iminoethers (2) and 5-aminoimidazole-4-carbonitrile (5) to give the 1,2-bridged adenine derivatives (7), most of which undergo spontaneous Dimroth rearrangement to afford the 2,N(6)-bridged adenines (8).