Synthesis of N-(2-phosphonylmethoxyethyl) derivatives of heterocyclic bases

Abstract

The preparation of N-(2-phosphonylmethoxyethyl) derivatives of purine and pyrimidine bases, IV, as analogs of the antiviral 9-(2-phosphonylmethoxyethyl)adenine (PMEA, I), is described. The synthesis consists in alkylation of alkali metal salts of heterocyclic bases or their N- or O-substituted derivatives with diethyl 2-p-toluenesulfonyloxyethoxymethylphosphonate (IIa), 2-chloroethoxymethylphosphonate (IIb) or 2-bromoethoxymethylphosphonate (IIc). The obtained N-(2-diethoxyphosphonylmethoxyethyl) derivatives of heterocyclic bases (III) were treated with bromotrimethylsilane to give phosphonic acids IV. Compounds IV were prepared from pyrimidines (uracil, cytosine and their 5-methyl derivatives), purines (adenine and its N6- and C(2)-substituted derivatives, hypoxanthine, guanine, 6-hydrazinopurine and 6-methylthiopurine etc.) and their analogs (3-deazaadenine etc.).