Purine studies. Part X. Further synthetic approaches to purines for the amplification of phleomycin activity against E. coli

Abstract

In view of the high amplifying activity shown by 6,9-dimethyl-2-methylthiopurine (1 : R = SMe), a number of analogues have been synthesised. These include derivatives having the C- or N-methyl group replaced by an ethyl group, homologues containing an additional 8-methyl or -ethyl group, and derivatives lacking the C- or the N-methyl group. Some related 2-ethylthio- and 2-dimethylamino-purines are also described, together with the 2-carbamoylmethylthiopurine (1; R = S·CH₂·CO·NH₂) and the oxidation product (1; R = SO₂Me) from (1; R = SMe). From the S-methylation of 6-ethyl-9-methylpurine-2(3H)-thione (3; R¹= Et, R²= Me), bis-(6-ethyl-9-methylpurin-2-yl) sulphide (4) was isolated as the major product.