To obtain a new compound useful as an antigen (hapten) for preparing a catalyst antibody having a catalytic mode for an aspartic protease.

This compound is represented by formula I (R1 and R2 are each H, NO2 or methoxy; and R3 is OH or 2-mercapto-propionamide), e.g. benzyl 2-amino-2-deoxy-3-amino-3-deoxy-4-O-benzyl-6-(2-mercapto)propionamide-b-D- allopyranoside ditrifluoroacetate. The compound represented by formula I in which R3 is 2-mercapto-propionamide is obtained by starting from D-glucosamine hydrochloride, passing through a compound represented by formula II (Phth is phthaloyl; and Bn is benzyl), etc., and providing a compound represented by formula III (Boc is tert-butyloxycarbonyl), reducing the resultant compound, then condensing the reduction product with N-hydroxysuccinimidyl pyridylthiopropionate, removing the Boc from the prepared product and subsequently reductively removing the thiopyridyl with dithiothreitol.