The present invention relates to compounds represented by the formula:
wherein ring H represents an optionally substituted aromatic heterocyclic group or an optionally substituted alicyclic hydrocarbon group; X and Y independently represent a single bond, —O—, a group of the formula: —S(O)m— wherein m is 0, 1 or 2, a group of the formula: —NR8— wherein R8 represents a hydrogen atom, an alkyl group or an acyl group, —CO— or an optionally substituted methylene group; —A—B— represents —N═CH—, —CH═N—, —N═N— or —CH═CH—; R1 represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group which may be bonded through a hetero atom or an acyl group; R2 and R3 independently represent a hydrogen atom, a halogen atom or an optionally substituted alkyl group; R4 represents a hydrogen atom or a halogen atom; R5 represents a hydrogen atom, an optionally substituted alkyl group or an acyl group; R6 and R7 independently represent a hydrogen atom or R6 and R7 may form a chemical bond together with each other; and D represents —CH2— or —CO—; or a salt thereof. These compounds and salts thereof are useful as anti-protozoal agents.