A great number of antiarrhythmic agents with 2,2,5,5-tetramethyl-3-pyrroline (and pyrrolidine)-3-carboxamide structure were synthesized. One of them A-2545 (1) was selected for further investigation aiming the elucidation of its chemical properties. The hydrolysis of 1 was studied, where theoretically seven hydrolysis products might be formed (2-8, Fig.1.). The hydrolysis takes place in aqueous solution of 1. HCl also at room temperature. In alkali-catalyzed process only one main product can be detected by TLC. This hydrolysis product was assigned as phthalamide acid (2) proved by chromatographic, thermic, GC-MS and NMR methods. An interesting behaviour of 2 upon GC-MS investigation (thermic and electron impact) is its recyclisation to 1 at the injector temperature (140 degrees) thus 2 appears in the mass spectrum as it would be A-2545 (Fig. 2. and 3.).