Abstract: An object of the invention is to provide compounds having a myocardial KD (Kinetic cell death)-inhibiting effect without being accompanied by a cardiodepressant effect.A 1,4-benzothiazepine derivative represented by the following Formula [I]: ##STR1## wherein each of substituent groups is defined as follows: R represents H or a C.sub.1 -C.sub.3 lower alkoxy group; X represents O or H.sub.2 ; n represents 1 or 2; R.sup.1 represents H, a substituted phenyl group wherein the substituent group is OH or a C.sub.1 -C.sub.3 lower alkoxy group, ##STR2## a C.sub.1 -C.sub.3 lower alkoxy group, ##STR3## wherein R.sup.2 represents a C.sub.1 -C.sub.3 acyl group, and ph represents a phenyl group, or a pharmaceutically acceptable salt thereof.

Abstract: Novel diphenylmethyl piperazine derivatives of this invention have a chemical structure represented by the following Formula [I]: ##STR1## wherein R represents ##STR2## The compounds have an effect of inhibiting the overcontraction and overextension of the myocardium without being accompanied by a myocardium-inhibiting effect. By using the novel diphenylmethyl piperazine derivatives as an effective ingredient, it is possible to obtain a myocardial necrosis inhibitor which can protect against myocardial necrosis, and a drug for the treatment and prevention of acute myocardial infarction.