{'fraction_non_alphanumeric': 0.02646868947708199, 'fraction_numerical': 0.02065848934796643, 'mean_word_length': 5.540084388185654, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
SPECTROSCOPIC PROPERTIES OF PSORALEN DERIVATIVES SUBSTITUTED BY CARBETHOXY GROUPS AT THE 3,4 AND/OR 4,5' REACTION SITE

Abstract— The newly synthesized linear psoralen derivative 3‐carbethoxypsoralen has been shown recently to behave as a monofunctional derivative and has attracted some interest in the psoriasis treatment. In a first attempt to understand, by the fluorescence technique, the molecular mechanism by which it interacts with DNA, a spectroscopic study of the molecule was undertaken. The fluorescence of 3‐carbethoxypsoralen at room temperature resembles that of 8‐methoxypsoralen with a ten times higher quantum yield. 365 nm irradiation of dilute solutions of 3‐carbethoxypsoralen rapidly leads to the formation of two types of highly fluorescent photoproducts. Type 1 photoproducts (λemmax= 425 nm, λexcmax= 360 nm) have been identified as the result of the addition of a solvent molecule to the 4,5' reaction site of the molecule. Their fluorescence intensity is a hundred times higher for 3‐carbethoxypsoralen than for 8‐methoxypsoralen. They become negligible when the 4',5' reaction site carries also a carbethoxy group. Type 2 photoproducts exhibit a somewhat different emission (λemmax = 443 nm, λexcmax= 413 nm). They are probably the result of an opening of the furocoumarin molecule. The implications of the peculiar photochemical properties of 3‐carbethoxypsoralen are discussed in view of its biological activity. In addition, the use of fluorescence in monitoring the photobinding of psoralens to DNA is also discussed