serotonin and serotonin3 (5-HT3) antagonists using a two-dimensional grid template composed of regular hexagons, we deduced structural modification patterns from agonists to antagonists, and designed new 5-HT3 antagonist prototypes. Among them, 2-(4-methyl-1-piperazinyl)-1-butylbenzimidazole (6) was identified as a lead compound which has potent 5-HT3 antagonistic activity comparable to that of granisetron
and eco-friendly method for the synthesis of o-nitroarylamine from o-nitroaryl sulfonic acid via ipso nucleophilic aryl substitution by amine is described. The products have been obtained with good yields at room temperature without the assistance of any metal, activating agent, or toxic oxidant. This method is useful for racemization-free synthesis of N-aryl amino acid esters.