Urea derivatives and their use as ACAT inhibitors

A compound of formula (I) or a pharmaceutically acceptable salt thereof ##STR225## in which:

• R.sub.1 and R.sub.2, which may be the same or different, each represents
• a hydrogen atom,
• a halogen atom,
• a straight or branched (C.sub.1 -C.sub.6)alkyl group or
• a straight or branched (C.sub.1 -C.sub.6)alkoxy group,
• R.sub.3 and R.sub.4, which may be the same or different, each represents
• a hydrogen atom,
• a straight or branched (C.sub.1 -C.sub.12)alkyl group,
• a straight or branched (C.sub.2 -C.sub.20)alkenyl group,
• a (C.sub.1 -C.sub.6)alkoxy(C.sub.1 -C.sub.6)alkyl group,
• a (C.sub.1 -C.sub.6)alkoxycarbonyl (C.sub.1 -C.sub.9)alkyl group,
• a benzyloxycarbonyl(C.sub.1 -C.sub.6)alkyl group in which the alkyl moiety is optionally substituted by phenyl,
• a N,N-di(C.sub.1 -C.sub.6)alkylamino(C.sub.1 -C.sub.6)alkyl group,
• a N-(C.sub.1 -C.sub.6)alkyl-N-benzylamino(C.sub.1 -C.sub.6)alkyl group,
• a (C.sub.1 -C.sub.6)alkylthio(C.sub.1 -C.sub.6)alkyl group,
• an oxo(C.sub.1 -C.sub.9)alkyl group,
• a hydroxy(C.sub.1 -C.sub.6)alkyl group,
• a dihydroxy(C.sub.1 -C.sub.6)alkyl group,
• a cyclo(C.sub.3 -C.sub.15)alkyl group,
• a cyclo(C.sub.3 -C.sub.8)alkyl(C.sub.1 -C.sub.6)alkyl group,
• a dicyclo(C.sub.3 -C.sub.9)alkyl(C.sub.1 -C.sub.6)alkyl group,
• a bicyclo(C.sub.6 -C.sub.9)alkyl group,
• a tricyclo(C.sub.9 -C.sub.12)alkyl group,
• in which in all cases the cycloalkyl group or the cycloalkyl moiety is optionally substituted by one or two substituents selected from the group consisting of (C.sub.1 -C.sub.6)alkyl, hydroxy, amino, acetoxy, acetamido, phenyl, benzyloxy, dimethylaminophenyl, and methylenedioxyphenyl, which may be further fused with a benzene ring,
• an aryl group,
• an aryl(C.sub.1 -C.sub.6)alkyl group,
• a diaryl(C.sub.1 -C.sub.6)alkyl group,
• in which in all cases the aryl group or the aryl moiety is optionally substituted by one, two or three substituents selected from the group consisting of (C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkyloxy, halogen, nitro, hydroxy, amino, dimethylamino, methylenedioxy, and pyrrolidinyl,
• a heterocyclic group or
• a heterocyclic group attached to a (C.sub.1 -C.sub.6)alkylene chain,
• in which in all cases the heterocyclic group represents a saturated or unsaturated, 5 to 8 membered ring monocyclic or bicyclic, heterocyclic group containing 1 to 3 heteroatoms selected from the group consisting of S, O and N, and the heterocyclic group is optionally substituted by one or two substituents selected from the group consisting of acetyl, hydroxy, (C.sub.1 -C.sub.9)alkyl, (C.sub.1 -C.sub.9)alkyloxy, cyclo(C.sub.3 -C.sub.8)alkyl, cyclo(C.sub.3 -C.sub.9)alkyl(C.sub.3 -C.sub.10)alkyl, pyridyl(C.sub.1 -C.sub.6)alkyl, phenyl, phenyl(C.sub.1 -C.sub.6)alkyl, diphenyl (C.sub.1 -C.sub.6)alkyl, and phenylpiperazinyl, the phenyl group or the phenyl moiety being optionally substituted by one or two substituents selected from the group consisting of halogen, hydroxy, (C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy, cyano, diethylamino and trifluoromethyl, which may be further fused with a benzene ring,
• and further R.sub.3 and R.sub.4, together with the nitrogen atom to which they are attached, may form a saturated or unsaturated heterocyclic group,
• in which the heterocyclic group represents a 5 to 8 membered ring monocyclic or bicyclic, heterocyclic group or a group derived from a heterocyclic spiro compound, which may contain one or two heteroatoms selected from the group consisting of S, O or N, the heterocyclic group being optionally substituted by one or two substituents selected from the group consisting of (C.sub.1 -C.sub.6)alkyl, hydroxy, hydroxy(C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy(C.sub.1 -C.sub.6)alkyl, acetoxy(C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.9)alkylcarbonyl, (C.sub.1 -C.sub.6)alkoxycarbonyl, amino, tosyl, phenyl, halogenophenyl, (C.sub.1 -C.sub.6)alkoxyphenyl, phenyl(C.sub.1 -C.sub.6)alkyl, benzyloxy, benzyloxy(C.sub.1 -C.sub.6)alkyl, tolyl, xylyl, benzoyl, methylenedioxyphenyl(C.sub.1 -C.sub.6)alkyl, pyridyl, pyridylcarbonyl, piperidyl, pyrrolidinyl (C.sub.1 -C.sub.6)alkyl and pyrrolidinylcarbonyl(C.sub.1 -C.sub.6)alkyl, which may be further fused with a benzene ring,
• in which in all cases the alkyl and alkoxy moieties may be either straight or branched,
• with the proviso that both R.sub.3 and R.sub.4 do not represent a hydrogen atom at the same time;
• R.sub.5 and R.sub.6, which may be the same or different, each represents a straight or branched (C.sub.1 -C.sub.6)alkyl group;
• and the line ##STR226## represents --CH.sub.2 CH.sub.2 -- or --CH.dbd.CH--.