Base‐catalyzed hydrolysis of 6‐aminopenicillanic acid. The kinetic and thermodynamic products

In the presence of sodium hydroxide or a β‐lactamase, 6‐APA has been shown to hydrolyze rapidly at room temperature to penicic acid 3, the kinetic product of the reaction. In a subsequent equilibration 3 isomerizes at C‐5, by way of intermediate imine 4, affording 5‐epi‐penicic acid 6 as the major hydrolysis product (∼ 95% at equilibrium). The pH and temperature parameters of equilibration are discussed and HPLC, optical rotation, proton nmr and 13C nmr data are presented.