GB744865A - Improvements relating to the preparation of 6-disubstituted-amino-purines - Google Patents

Abstract

Purine derivatives of the formula <FORM:0744865/IV(a)/1> where R1 and R2 are alkyl, mononuclear aryl or mononuclear aralkyl, or form a 6-membered ring with the nitrogen atom, are prepared by (1) contacting with a low temperature Raney nickel catalyst the corresponding compounds having in the 2-position a substituted mercapto group and in the 8-position hydrogen or a free or substituted mercapto group; or (2) ring-closing a 4-amino-5-formamido-6-NR1R2-pyrimidine by heating to 150-300 DEG C., preferably 200-275 DEG C. Process (1) is preferably conducted at 80-110 DEG C. in aqueous alkaline solution, e.g. 0.1N-2N sodium hydroxide. Other solvents may however be used instead, e.g. alcohols, glycols, glycol ethers or aromatic hydrocarbons, and the temperature may range from 25 DEG to 150 DEG C. Method (2) may be carried out in the presence or absence of a solvent, in the latter case the pyrimidine being heated at least to fusion point. Suitable solvents are quinoline, formamide, glycol and diphenyl ether. The products form salts with strong acids such as hydrochloric, sulphuric, phosphoric and picric. They also react with bases to give e.g. alkali metal, alkaline earth metal, silver and chloromercury derivatives. They can be converted into compounds analogous to adenosine. Examples show the production of the following 6-substituted purines by both methods: 6-dimethylamino, 6-diethylamino and 6 - methylanilino; also of 6 - piperidino-purine and 6-n-butylbenzylamino-purine by method (1). 2 - (Substituted mercapto) - 6 - NR1R2-purines are made as in Specification 744,866 from the appropriately 2:6-di-substituted 4-aminopyrimidines via the 5-nitroso, 5-amino and 5-formylamino derivatives. 2 - (Substituted mercapto) - 6 - NR1R2 - 8-mercapto-purines are prepared as in Specification 744,869 from the corresponding 2:6-disubstituted - 4:5 - diamino - pyrimidines and carbon disulphide. 2:8 - Di - (substituted mercapto) - 6 - NR1R2-purines are made by alkylating the preceding compounds. An example is given of the production of 2:8-di-(methylmercapto)-6-dimethylaminopurine. 4 - Amino - 5 - formylamino - 6 - NR1R2-pyrimidines are obtained as in Specification 744,868 by elimination of a 2-(substituted mercapto) group. 2 - (Substituted mercapto) - 4 - amino - 6-NR1R2-pyrimidines are described in Specification 744,867.