Synthesis and biological activity of the four stereoisomers of 6-[4-[3-[[2-hydroxy-3-[4-[2- (cyclopropylmethoxy)ethyl]phenoxy]propyl]amino]-propionamido] phenyl]-5-methyl-4,5-dihydro-3(2H)-pyridazinone, a combined vasodilator and beta-adrenoceptor antagonist.

6-[4-[3-[[2-Hydroxy-3-[4-[2- (cyclopropylmethoxy)ethyl]phenoxy]propyl]amino]propionamido] phenyl]- 5-methyl-4,5-dihydro-3(2H)-pyridazinone (3) consists of a mixture of four stereoisomers, i.e., two racemates, as a consequence of the two asymmetric centers contained in the structure. An approximately equimolar mixture of these two racemates exhibits a novel combination of vasodilation and beta-adrenergic antagonist activity. This paper describes the synthesis of each of the four possible stereoisomers of 3 and provides clear evidence for the different pharmacological profile of each of the stereoisomers. The RA,SB isomer 3a has an overall profile slightly better than the complete mixture; the other three isomers all show reduced activity as vasodilators and/or beta-adrenergic antagonists.