Synthesis of the Optically Active trans-Isomers of Diltiazem and Their Cardiovascular Effects and Ca-Antagonistic Activity.

Optically active trans-isomers of diltiazem were synthesized and their cardiovascular effects were evaluated in anesthetized dogs and in isolated guinea pig hearts. Both (+)-2 (2R,3S) and (-)-2 (2S,3R) were much less active than diltiazem (1, 2S,3S) with short duration of action. No substantial enantiomeric difference in activity was seen between them. Their Ca-antagonistic activities on Ca(2+)-induced contractions in K(+)-depolarized canine basilar arteries were also examined. Absolute stereochemistry of (+)-2 was determined to be 2R,3S by X-ray crystallographic analysis.