Identification of photoproducts of hexahydroquinoline derivatives by GC-EI-MS and HPLC-ESI-MS.

Photoproducts of hexahydroquinoline derivatives have been analyzed with gas chromatography electro ionization-mass spectrometry (GC-EI-MS) and high performance chromatography electrospray ionization-mass spectrometry (HPLC-ESI-MS). The study was performed on four HHQ derivatives: 2,6,6-trimethyl-3-carbomethoxy-5-oxo-4-(R-phenyl)-1,4,5,6,7,8-hexahydroquinoline; R=2'-Me, 3'-Me, 2'-MeO, and 3'-MeO. The photochemical degradation of each of the HHQ derivatives led to the appearance of one product. The photoproducts were identified as the corresponding tetrahydroquinoline analogues, which were formed by dehydrogenation of dihydropyridine moiety. In GC-mass spectra, the most frequent way of fragmentation was elimination of CH3* or CH3O* radical of the ester group. In the photoproducts substituted at 2'-position of the phenyl ring, elimination of isobutene (C4H8) was observed. In the photoproducts with 3'-position substituents, elimination of COOCH3* radical was noted.

Gas chromatography-mass spectrometry identification of photoproducts of hexahydroquinoline derivatives: potential calcium channel antagonists.

Photodegradation products of hexahydroquinoline derivatives (HHQ) have been analysed with gas chromatography-mass spectrometry (GC-MS). The photodegradation was carried out under the conditions recommended in the first version of the document issued by the International Conference on Harmonization (ICH), currently in force in the studies of photochemical stability of drugs and therapeutic substances. The study was performed on the compounds having two chlorine atoms at different positions of the phenyl ring. Photodegradation of dichlorophenyl derivatives of HHQ resulted in formation of one or three photoproducts. The main product of their decomposition was aromatic compound formed as a result of dehydrogenation of the dihydropyridine ring. The most often observed fragmentation pathway of the photoproducts formed was elimination of methyl and methoxy radicals from the ester groups. The fragmentation of the photoproducts containing one chlorine atom at the ortho-position of the phenyl ring occurred through elimination of chlorine radical.

Photochemical study of hexahydroquinoline derivatives--a new group of calcium antagonists.

The photochemical stability of 2,6,6-trimethyl-3-carbmethoxy-4-phenyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline (HHQ) derivatives with different substituents on the phenyl ring (-Cl, -NO2, -CF3, -CH3, -OCH3) has been studied. The process of photodegradation was studied by UV spectrophotometry. The rate of photodegradation was found to depend on the type and position of the substituent in the phenyl ring. The compounds most susceptible to the damaging effect of light proved to be those containing the nitro group, in particular with the substituent in the ortho position of the aromatic ring. Derivatives with alkyl (-CH3) and halo-alkyl (-CF3) substituents showed the greatest photochemical stability. The compounds with substituents in the ortho position were found to be much less photostable than the meta isomers. The quantum yield values obtained ranged from 10(-4) to 10(-3), indicating the occurrence of secondary photochemical processes initiated by the primary products of decomposition.

Photochemical Study of Hexahydroquinoline Derivatives - A New Group of Calcium Antagonists.

The photochemical stability of 2, 6, 6-trimethyl-3-carbmethoxy-4-phenyl-5-oxo-1, 4, 5, 6, 7, 8-hexahydroquinoline (HHQ) derivatives with different substituents on the phenyl ring (-Cl, -NO(2), -CF(3), -CH(3), -OCH(3)) has been studied.The process of photodegradation was studied by UV spectrophotometry. The rate of photodegradation was found to depend on the type and position of the substituent in the phenyl ring. The compounds most susceptible to the damaging effect of light proved to be those containing the nitro group, in particular with the substituent in the ortho position of the aromatic ring. Derivatives with alkyl (-CH(3)) and halo-alkyl (-CF(3)) substituents showed the greatest photochemical stability. The compounds with substituents in the ortho position were found to be much less photostable than the meta isomers. The quantum yield values obtained ranged from 10(-4) to 10(-3), indicating the occurrence of secondary photochemical processes initiated by the primary products of decomposition.