SYNTHESIS OF BETA-D-RIBONUCLEOSIDES DERIVED FROM DIPYRAZOLO[3,4-B 3',4'-D]PYRIDIN-3-ONE SYSTEM/

The new ribonucleosides )-2H,6H-dipyrazolo[3,4-b:3',4'-d]pyridin-3(5H) -one (1a) and )-2H,6H-dipyrazolo[3,4-b:3',4'-d]pyridin-3(5H)-one (1b) were prepared from stannic chloride-catalyzed ribosylations of the cor responding heterocycles 6a and 6b. Attempts of de-O-benzoylation of la and Ib failed to give the free ribosides 1c and 1d. The effect of com pounds 1a, 1b, 6a and 6b on the catalytic activities of reverse transc riptase from recombinant immunodeficiency virus type 1 was evaluated. Compounds Ib and 6b inhibited the RNA dependent DNA polymerase activit y of the enzyme by more than 50% at a concentration of 70 mu M. In con trast, human placental DNA polymerase activities alpha and epsilon wer e unaffected by this concentration. The structures of the nucleosides are supported by 1D and 2D-nmr techniques (nOdes, HMBC and HMQC experi ments).