PURPOSE: To obtain a new 2-carboxysuccinic acid imide derivative having an aldose reductase-inhibiting action low in toxicity and useful for treating and preventing various kinds of diabetic complications such as cataract retinopathy keratopathy neuropathy and nephritis.CONSTITUTION: A 2-carboxysuccinic acid amide derivative of formula I (R(sup 1) is H halogen; R(sup 2) is halogen; R is a group for protecting a carboxyl group; the wave line exhibits that the steric configuration of the 3-carbon ...