Abstract
The α‐hydroxybenzylphosphonates 1a–1j of the antiviral drug 3′‐azido‐2′,3′‐dideoxythymidine 5 (AZT) as potential lipophilic prodrugs were readily accessible in 49% to 87% yield via a four‐step synthetic pathway introducing the modifications in the aromatic ring system in the last step by making use of intermediate 6. All compounds 1a–1j exhibited higher partition coefficients in 1‐octanol/water than AZT (5). In hydrolysis studies at pH 7.5 we observed that precursors to bioactive compounds were delivered by simple hydrolysis of the lipophilic precursors 1a–1j via two different mechanisms: the phosphonate‐phosphate rearrangement leading to the benzylphosphotriesters 2 and/or the direct cleavage into the di‐AZT phosphonate 6. Both compounds 2 and 6 were further degraded yielding the potentially antiviral active compounds 4 and 8, respectively. The hydrolysis pathway could be controlled by the substitution pattern in the benzylic moiety. Identical hydrolytic behavior of 1 was detected in „biological”︁ hydrolysis kinetics by using a RPMI culture medium containing 10% heat‐inactivated fetal calf serum (FCS). The title compounds 1a–1j exhibited considerable HIV‐1 and HIV‐2 activity in wild‐type CEM/O cells.