The present invention provides to a novel compound having an ACAT inhibiting activity.The present invention relates to compounds represented by formula (I) 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 —NR4—, an oxygen atom, a sulfur atom, a sulfoxide or a sulfone, Z represents a single bond or —NR5—, R4 represents a hydrogen atom, a lower alkyl group, an aryl group or an optionally substituted silyl lower alkyl group, R5 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.