The present invention provides to a novel compound having an ACAT inhibiting activity.The present invention relates to compounds represented by formula (I) ##STR00001## wherein represents an optionally substituted divalent residue such as benzene, pyridine, cyclohexane or naphthalene, or a group, Het represents a 5- to 8-membered, substituted or unsubstituted heterocyclic group containing at least one heteroatom selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom, such as a monocyclic group, a polycyclic group or a group of a fused ring, X represents --NH--, an oxygen atom or a sulfur atom, Y represents --NR.sub.4--, an oxygen atom, a sulfur atom, a sulfoxide or a sulfone, Z represents a single bond or --NR.sub.5--, R.sub.4 represents a hydrogen atom, a lower alkyl group, an aryl group or an optionally substituted silyl lower alkyl group, R.sub.5 represents a hydrogen atom, a lower alkyl group, an aryl group or an optionally substituted silyl lower alkyl group, and n is an integer of from 1 to 15, or salts or solvates thereof, and a pharmaceutical composition containing at least one of these compounds.