Since the mid-80s, an increase in malignant skin disease has been observed, especially in the case of westerners. The reason for this has also been established, mainly an increased exposure to sunlight. So cosmetic UV filters gain in importance for sun protection, because of the problematic nature of UV irradiation. In particular, there are only a few liscensed UV A filters and some filter possess disadvantages like low photostability, watersolubility, exclusivity (patent restrictions). Quinoxaline is the basic structure for the development of UV B-, UV A- UV B/ A broad band filter. In addition, quinoxaline has paricular UV B absorption properties, is easily accessible and has a structure that is readily modifiable. To achieve this, a series of derivatives of specific absorption ranges are synthesized by introducing specific substituents in the basic structure. In view of the effects of the substituents in the synthesized qunoxalines the influences on the UV absorption are investigated. A calculation of the electronic transitions of the structures is carried out using a semiempirical program and the results are compared with the experimental UV data. The calculated wavelengths showed good correlation with the experimental data, however the intensities of the absorptions deviated in a higher degree from the measured values. An easily access to condensed quinoxalines is established by developing new synthesis methods. The UV spectra of pyrrolo[2,3-b]- and imidazo[4,5-b]quinoxalines are characterized by intensities in the mid-UV A range. Investigations of the quinoxalines, paricularly arylimidazo[4,5-b]quinoxalines, in cosmetic solvents showed that the absorption properties after UV irradiation are retained and the compounds are highly photostable. | English |
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