PHOTODECOMPOSITION OF A NEW 1,4-DIHYDROPYRIDINE - FURNIDIPINE

The photodecomposition of new 1,4-dihydropyridine, furnidipine (CRE-31 9); -nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid 3-tetrahyd rofurfuryl 5-methyl diester) was studied by voltammetric, UV-vis spect rophotometric, and HPLC technique with three different light condition s (artificial daylight, UV light, and room daylight). The artificial d aylight photodecomposition of furnidipine follows 0.5-order kinetics a s assessed by the above-mentioned techniques. Furthermore, the dayligh t photoderivative was isolated and identified by NMR and IR as ethyl-4 -(2-nitrosophenyl)pyridine-3,5-dicarboxylic acid 3-tetrahydrofurfuryl 5-methyl diester. Quantitative kinetic data for the UV photodecomposit ion of furnidipine cannot be obtained due to both the high rate of deg radation (< 1 min) and intermediate reactions. However, polarographic, spectroscopic, and chromatographic evidence permits us to identify th is photoproduct as imethyl-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-tetrahydrofurfuryl 5-methyl diester. Polarography was the most useful technique to assess the photodegradation of this drug from the qualitative point of view, and quantitative kinetic data were similar to those obtained by HPLC and UV-vis spectroscopy.