This invention relates to a novel compound represented by the formula (I): ##STR00001## or a pharmaceutically acceptable salt thereof, wherein R.sup.1 is --S(O)p-A, --S--(O)q-B or --O-D, wherein p and q, which are the same or different, each represent an integer from 0 to 2, A is a straight chain C1-C10 alkyl group which may be substituted by R.sup.10, and B and D each independently represent R.sup.12 which may be substituted by R.sup.10; R.sup.2 is a hydrogen atom, a halogen atom, or a straight chain or branched C1-C6 alkyl group which may be substituted by R.sup.10; X.sup.1 and X.sup.2 each independently represent N or CH, but cannot both be N; the formula (II): ##STR00002## shows a monocyclic or bicyclic heteroaryl group which has a nitrogen atom adjacent to the carbon atom bonded to the amide group, and the heteroaryl group may be substituted by R.sup.10; R.sup.10 is R.sup.11, or a hydrocarbon group which may be substituted by R.sup.11; R.sup.11 is, for example, a hydrogen atom or amino; and R.sup.12 is, for example, phenyl, thiazolyl, pyridyl or methylene dioxyphenyl. The compound according to this invention has a glucokinase activation effect, and for example, is useful in the treatment and prevention of diabetes mellitus, and in the prevention of its complications such as diabetic nephropathy, diabetic retinopathy, diabetic neuropathy and diabetic arteriosclerosis.