A compound represented by the following general formula (I) or a salt thereof, or a solvate thereof: ##STR00001## (wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are the same or different, and represent hydrogen atom, a halogen atom, a lower alkyl group etc., R.sup.6, R.sup.7 and R.sup.8 are the same or different, and represent hydrogen atom, a halogen atom, a lower alkyl group etc., R.sup.9 and R.sup.10 are the same or different, and represent hydrogen atom, a lower alkyl group, a (lower cycloalkyl)(lower alkyl) group etc., and R.sup.11 represents hydrogen atom, a halogen atom, a lower alkoxy group, a (lower alkyl)thio(lower alkoxy) group, a (lower alkyl)sulfinyl(lower alkoxy) group, a (lower alkyl)sulfonyl(lower alkoxy) group etc.), which has potent inhibitory activity on CETP.