Since the discovery of 2, 2′-dimethoxycarbonyl-4, 4-dimethoxy-5, 6, 5′, 6′- biomethylenedioxy-biphenyl (DDB) as a potent anti-HBV agent, we have studied the structure–activity relationships of 4, 4′-dimethoxy-5, 6, 5′, 6′-dimethenedioxy-2- alkyloxycarbonyl-2′-(4-substituted benzyl piperazin-1-yl) carbonyl-biphenyl as anti-HBV agents. Therefore, it is rational to extend this study to the 3, 3′-disustituted-4, 4′- ...