Spectral and kinetic properties of an immunoactive 8-azasteroid and a product of its photochemical transformation in aqueous solutions

The spectral and kinetic properties of an immunoactive 8-azasteroid and a product of its photochemical transformation are studied by the methods of steady-state and transient spectroscopy. It is found that the spectral features of the studied compounds in solvents of different nature are determined by a high sensitivity of the electronic structure of the aminovinyldicarbonyl fragment to intermolecular interactions of the donor-acceptor type. This leads to the existence in solutions of several mesomeric-tautomeric forms that are in a dynamic equilibrium controlled by the experimental conditions. Based on the analysis of the dynamics of the transient spectra of induced absorption and of the spectral and luminescent properties of the extracted photoproduct, the conclusion is made on the direction of the photochemical transformation of 2,3-dimethoxy-8-azagona-1,3,5(10),13-tetraene-12,17-dione and the final product is identified as 6,7-dehydroderivative of the parent compound.