Synthesis of racemic and enantiomeric 3-pyrrolidinyl derivatives of nucleobases

The synthesis of novel 3-pyrrolidinyl derivatives of nucleobases is described. Starting from malic acid, we improved the synthesis of both racemic and optically active N-benzyl-3-hydroxypyrrolidine-2,5-diones, which were transformed in four steps into N-tert-butyloxycarbonyl-3-mesyloxypyrrolidines, the key synthons for the alkylation of purine and pyrimidine nucleobases. Alkylations of cesium salts of purines and sodium salts of pyrimidines with N-tert-butyloxycarbonyl-3-mesyloxypyrrolidines proceeded smoothly, giving high yields of 9-substituted purine derivatives and moderate yields of 1-substituted pyrimidine derivatives. Using (S)-N-tert-butyloxycarbonyl-3-mesyloxypyrrolidine as the same intermediate for the synthesis of both enantiomeric N-Boc-3-pyrrolidinyladenines, and considering the results obtained on chiral HPLC analysis of the products, we proved that nucleophilic displacement of the mesyloxy group proceeded with inversion and not with retention of the configuration. Prepared compounds were tested for cytostatic and antiviral properties, but no significant activity was found.