PURINE STUDIES .6. FORMATION, HYDROLYSIS, AND AMINOLYSIS OF SOME PURINE SULPHOXIDES AND SULPHONES

The action of diazomethane on 2-, 6-, or 8-methylthiopurine gives a separable mixture of the appropriate 9-methyl derivative and a by-product, respectively N(1 or 7),8-dimethyl-2-, 3-methyl-6-, or 3-methyl-8-methylthiopurine. Each 9-methylated methylthiopurine can be oxidised by m-chloroperbenzoic acid to the corresponding sulphoxide and sulphone. These undergo hydrolysis in N-sodium hydroxide at rates which vary little from sulphoxide to sulphone but which show a marked positional order: 8 > 6 ≫ 2. 9-Methyl-6-methylsulphinylpurine reacts with ethanolic piperidine four times faster than the corresponding sulphone or chloro-analogue. The 1H n.m.r. spectrum of each methylthiopurine shows a significant downfield shift (ca, 0.5 p.p.m.) of the H-8 peak on changing solvent from deuteriochloroform to [2H6]dimethyl sulphoxide: peaks for H-2 and H-6 show much smaller shifts in either direction.