Enantiomerization and hydrolysis of (±)-7-chloro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide by stopped-flow multidimensional high-performance liquid chromatography

A novel stopped-flow multidimensional HPLC (sf-MD-HPLC) procedure has been developed to investigate simultaneously the effect of the pH on the enantiostability and hydrolysis of (±)-7-chloro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide [(±)IDRA21]. It was possible to determinate the rate constants and free energy barriers of enantiomerization and hydrolysis rate constants of (±)IDRA21, by using two chiral stationary phases (CSPs) and one achiral C18 column. A classical batchwise kinetic method was used to calculate rate constants of hydrolysis at the same temperature and in the same buffers used in sf-MD-HPLC. The good agreement of the results obtained validate the sf-MD-HPLC procedure. Furthermore, hydrolysis rate constants of (±)IDRA21 were calculated in a series of buffers over a pH range of 1.20-10.60 at 37 °C in order to evaluate the influence of the pH on hydrolysis.