Pterins. VII. Preparation of 6,6-dimethyl-5,6,7,8-tetrahydropterin hydrochloride

Abstract

The preparation of 6,6-dimethyl-5,6,7,8-tetrahydropterin (5) hydrochloride, a possible substrate for the phenylalanine hydroxylating system, has been achieved by trimethylsilylating 6-methyl-7,8- dihydropterin, reacting with methyllithium and removing the trimethylsilyl groups. Attempts to prepare this pterin by intramolecular cyclization of 2,5-diamino-6-(2'-hydroxy-2'-methylpropyl)-aminopyrimidin-4(3H)-one (17) gave the isomeric 5,8-diamino-3,3-dimethyl-2,3-dihydroimidazo- [1,2-clpyrimidin-7(1H)-one (20).