3‐Alkyl‐ and 3‐Aryl‐7H‐furo[3, 2‐g]‐1‐benzopyran‐7‐ones: Synthesis, Photoreactivity, and Fluorescence Properties

A series of 3‐alkyl‐ and 3‐aryl‐7H‐furo[3, 2‐g]‐1‐benzopyran‐7‐ones, known as linear furocoumarins, was synthesized and evaluated for their dark‐ and photobinding (crosslink formation) with DNA as well as for their spectrophotometric and fluorescent properties, lipophilicity, and ability to photobleach N, N‐dimethyl‐p‐nitrosoaniline (RNO) after irradiation with UVA light. 8‐Methoxypsoralen (8‐MOP, 9‐methoxy‐7H‐furo[3, 2‐g]‐1‐benzopyran‐7‐one) and 4, 5′, 8‐trimethylpsoralen (TMP, 2, 5, 9‐trimethyl‐7H‐furo[3, 2‐g]‐1‐benzopyran‐7‐one) were used as reference compounds in all tests. The investigations support the formation of a molecular complex between the furocoumarins and DNA.Crosslink formation with DNA after irradiation with UVA light was detectable for compounds with a methyl or phenyl substituent in position 3, but not for those bearing either a tert‐butyl, a 4‐methoxyphenyl, or a 2, 5‐dimethoxyphenyl group. All furocoumarins exhibited sufficient absorption in the UVA wavelength range and are fluorescent. All compounds showed a higher lipophilicity than 8‐MOP. Generally the 3‐alkyl substituted furocoumarins had a capacity to photobleach RNOwhich was higher than that of the 3‐aryl substituted ones. Some of the 3‐aryl substituted furocoumarins displayed a photobleaching ability which was similar to or lower than that of 8‐MOP.