Abstract Reaction of 8-bromoadenine derivatives 1 with thiourea in ethanol or butanol was used for the synthesis of the corresponding N 9-substituted 6-amino-7H-purine-8 (9H)- thiones 2. 8-(Methylsulfanyl) adenine derivatives 3 were prepared by reaction of thiones 2 with iodomethane in 1 M sodium methoxide or in aqueous 1.5 M potassium hydroxide. Alkylation of 6-amino-7H-purine-8 (9H)-thione (2a) proceeds preferentially on the sulfur ...