Synthesis and Biological Activity of Strongly Fluorescent Tricyclic Analogues of Acyclovir and Ganciclovir

In search of strongly fluorescent tricyclic analogues of acyclovir (ACV, 1) and ganciclovir (GCV, 2), derivatives of the 3,9-dihydro-9-oxo-5H-imidazo[1,2-a]purine system, several 6-[4-(acyloxy)phenyl], 6-[4-(acylamino)phenyl], and 6-[4-(phenoxycarbonyloxy)phenyl]-substituted TACV and TGCV analogues were synthesized and evaluated for their activity against herpes simplex virus types 1 and 2 in cell culture. All TACV and TGCV analogues showed strong fluorescence (quantum yield of 30-65% vs 2-aminopurine 100%). The 6-[4-(phenoxycarbonyloxy)phenyl]-substituted compounds 11 and 19 displayed the best combination of the fluorescence and antiviral potency.