Compounds are described of the formula <CHEM> wherein R1 and R4 independently represent a C1-4 alkyl group; R2 and R3 independently represent a C1-6 straight or brached alkyl chain or alkoxy group; R4 represents a C1-4 alkyl group; R5 represents a group CH=CR6R7 where R6 is a hydrogen atom or C1-3 alkyl group and R7 represents an aryl, pyridyl or cyano group; or R5 represents the group C IDENTICAL CR8 where R8 is an aryl group. The compounds represented by formula (1) reduce intracellular calcium ion concentration by limiting transmembranal calcium ion influx and thus may be useful for the treatment of cardiovascular disorders such as hypertension.
