Figure 1.

Scheme of the reaction catalyzed by antibody 4B2. 4B2 catalyzes allylic rearrangement of α-cyclopent-1-en-1-yl-p-acetamidophenone 2 to α-cyclopentylidien-p-acetamidophenone 4 via the enediol intermediate 3, 2-[4-(1-carboxy)propylamidobenzylamino]-3,4,5,6-tetrahydropyridinium. 1a is the hapten used to generate 4B2. The structure that was determined is that of the complex of 4B2 with 2-(4-aminobenzylamino)-3,4,5,6-tetrahydropyridinium 1b. Antibody 5C8 was generated against hapten 5a, and its x-ray structure was determined in the presence of inhibitor 5b (12).