The enzymatic synthesis of nucleoside analogues

Abstract

Ribavirin, 1--D-ribofuranosyl-1,2,4-triazole-3-carboxamide, is a broad spectrum antiviral agent active against both DNA and RNA viruses. A range of 1,2,3-triazole, 1,2,4-triazole and benzotriazole analogues of ribavirin was synthesised using a crude extract of N-deoxyribosyltransferases from Lactobacillus leichmannii in the chemoenzymatic synthesis of nucleoside analogues with potential antiviral activity. N-Deoxyribosyltransferase catalyses the transfer of the 2-deoxyribose sugar between purine and pyrimidine bases. Of thirty two bases synthesised, twelve were found to act as acceptors in the N-deoxyribosyltransferase reaction. Nine 2'-deoxyribofuranosyl-1,2,4-triazole nucleoside analogues were isolated and characterised. Only one nucleoside showed any significant antiviral activity. 2'-Deoxyribavirin was found to possess antiviral activity against the influenza virus. Attempts were made to synthesise the nucleoside chemical from ribavirin on a larger scale, but without success. However, 5'-iodo-5'-deoxyribavirin and 5'-deoxyribavirin were synthesised, the former showing slight antiviral activity. The specificities of the N-deoxyribosyltransferases for purine, pyrimidine and triazole bases are discussed, gathering together the findings of previous workers with the results presented in this thesis