Synthesis of Enantiomeric N-(2-Phosphonomethoxypropyl) Derivatives of Purine and Pyrimidine Bases. II. The Synthon Approach

Abstract

Another approach to (R)- and (S)-N-(2-phosphonomethoxypropyl) derivatives of purine and pyrimidine bases (PMP derivatives) I and II is described, consisting in alkylation of the heterocyclic base with (R)- and (S)-2-[bis(2-propyl)phosphonylmethoxy]propyl p-toluenesulfonates (X and XVIII) followed by transsilylation of the intermediary N-[2-bis(2-propyl)phosphonylmethoxypropyl] derivatives XI and XIX. The key intermediates X and XVIII were obtained from 1-benzyloxypropanols VI and XIV by two routes: (i) condensation with bis(2-propyl) p-toluenesulfonyloxymethylphosphonate (XIII), hydrogenolysis of the obtained 1-benzyloxy-2-bis(2-propyl)phosphonylmethoxypropanes VIII and XVI over Pd/C to 2-bis(2-propyl)phosphonylmethoxypropanols IX and XVII and tosylation of the latter or (ii) chloromethylation of compounds VI and XIV and subsequent reaction of the chloromethyl ethers VII and XV with tris(2-propyl) phosphite and further processing of the benzyl ethers VIII and XVI analogous to the enantiomeric propanols IX and XVII. This approach was used for the synthesis of derivatives of adenine (Ia, IIa), 2,6-diaminopurine (Ib, IIb) and 3-deazaadenine (Ic, IIc). Their guanine counterparts Ie and IIe were prepared by hydrolysis of 2-amino-6-chloropurine intermediates XId and XIXd. 6-Chloropurine was converted into diester XIi by reaction with tosylate X, which on reaction with thiourea and subsequent ester cleavage afforded the 6-thiopurine derivative Ij. Analogously, 2-amino-6-chloropurine derivative XId reacted with thiourea to give 9-(R)-(2-phosphonomethoxypropyl)-2-thioguanine (If), or with dimethylamine under formation of (2-phosphonomethoxypropyl)-2-amino-6-dimethylaminopurine (Ig). Hydrogenolysis of compound XId gave 9-(R)-(2-phosphonomethoxypropyl)-2-aminopurine (Ik). Hydrolytic deamination of adenine derivatives Ia and IIa led to enantiomeric (2-phosphonomethoxypropyl)hypoxanthines Ih and IIh.