Synthesis of benzimidazole derivatives as potential H1-antihistaminic agents

Several types of benzimidazole derivatives were prepared and were screened for H ₁-antihistaminic activity. Most of the compounds showed potent antihistaminic activity in vitro. Among them 2-(1-piperazinyl)methyl]-benzimidazoles 14 and 2-(1-homopiperazinyi)methyl]benzimidazoles 15 exhibited potent activity also in vivo.