Novel thiazolo[3,2-a]benzimidazol derivatives represented by general formula (1), which act specifically on metabotropic glutamate receptors and are useful as drugs; and novel compounds useful as intermediates for the synthesis of the derivatives wherein, R 1 is optionally substituted carbamoyl, carbonyl, oxy, amino, carbonylamino, or the like; R 2 is hydrogen, lower alkyl, or the like; and R 3 , R 4 and R 5 are each independently hydrogen, lower alkyl, or the like.