Synthesis and Biological Properties of C-2 Triazolylinosine Derivatives

O-6-(Benzotriazol-1H-yl)guanosine and its 2'-deoxy analogue are readily converted to the O-6-allyl derivatives that upon diazotization with t-BuONO and TMS-N-3 yield the C-2 azido derivatives. We have previously analyzed the solvent-dependent azide center dot tetrazole equilibrium of C-6 azidopurine nucleosides, and in contrast to these, the O-6-allyl C-2 azido nucleosides appear to exist predominantly in the azido form, relatively independent of solvent polarity. In the presently described cases, the tetrazole appears to be very minor. Consistent with the presence of the azido functionality, each neat C-2 azide displayed a prominent IR band at 2126-2130 cm(-1). A screen of conditions for the ligation of the azido nucleosides with alkynes showed that CuCl in t-BuOH/H2O is optimal, yielding C-2 1,2,3-triazolyl nucleosides in 70-82% yields. Removal of the silyl groups with Et3N center dot 3HF followed by deallylation with PhSO2Na/Pd(PPh3)(4) gave the C-2 triazolylinosine nucleosides. In a continued demonstration of the versatility of O-6-(benzotriazol-1H-yl)purine nucleosides, one C-2 triazolylinosine derivative was converted (t)o two adenosine analogues via the:se intermediates, under mild conditions. Products were desilylated for biological assays. The two C-2 triazolyl adenosine analogues demonstrated pronounced antiproliferative activity in human ovarian and colorectal carcinoma cell cultures. When evaluated for antiviral activity against a broad spectrum of DNA and RNA viruses, some of the C-2 triazolylinosine derivatives showed modest inhibitory activity against cytomegalovirus.