wherein the symbols have the following meanings:

R¹: —CO₂H, —CO₂-lower alkyl, or a tetrazolyl group,

R²: H, halogen, lower alkyl, or —O-lower alkyl,

R³: H, lower alkyl, or halogen,

R⁴: —CN, —NO₂, —Br, halogeno-lower alkyl, or —(CO)-lower alkyl,

R⁵: H, lower alkyl, —O-lower alkyl, halogen, —NO₂, or —CN,

X: —O—, —N(R⁷)—, or —S—,

wherein the group represented by R₄ is bonded to the phenyl group at the meta- or para- position relative to the thienyl group and the group represented by —X—R⁶ is bonded to the phenyl group at the meta- or para- position relative to the thienyl group,

R⁷: H or lower alkyl,

R⁶: linear or branched alkyl having 1 to 8 carbon atoms, linear or branched alkenyl having 3 to 8 carbon atoms, —Y-(cycloalkyl which may contain an oxygen atom), —Y-phenyl, or —Y-heteroaryl,

where the linear or branched alkyl having 1 to 8 carbon atoms, linear or branched alkenyl having 3 to 8 carbon atoms, cycloalkyl which may contain an oxygen atom, phenyl, and heteroaryl may be substituted with a group selected from the group consisting of hydroxy, —CN, —O-lower alkyl, —S-lower alkyl, —NR⁹(R⁹), and —(CO)NR⁹(R⁹),

Y: a bond, lower alkylene, or lower alkenylene,

R⁸ and R⁹: the same or different from each other, H or lower alkyl,

where, when X is a group represented by —N(R⁷)—, R⁷ and R⁶ may be combined together with the nitrogen atom to form a nitrogen-containing saturated heterocycle and the nitrogen-containing saturated heterocycle may be substituted with an lower alkyl.