In search of more potent, less toxic and selective potassium channel openers, thirteen N-(3,4- dihydro-2H-1-benzopyran-4-yl)isothiourea derivatives were synthesized and evaluated for vasorelaxant activity against 30 mmol•L^－1 KCl inducing contraction of rat aorta in vitro. Their structures were confirmed by spectral data and elemental analysis. The preliminary bioassay suggested that these compounds exhibited some vasorelaxant activities at a con-centration of 1×10^－5 mol•L^－1. The compound 6l also showed a good vasorelaxant activities at a 1×10^－6 mol•L^－1 concentration.

Key words: potassium channel opener, N-(3,4-dihydro-2H-1-benzopyran-4-yl)isothiourea, vasorelaxant activity