For establishment of the structure-activity relationship, 19 heterobicycle-coumarin conjugated compounds with the -SCH2- linker were synthesized and found to possess significant antiviral activities. Prominent examples included imidazopyridine-coumarin 12c, purine-coumarin 12d, and benzoxazole-coumarin 14c, which inhibited HCV replication at an EC50 of 6.8, 2.0, and 12 mu M, respectively. The heteroatoms in bicycles
