The near-UV induced photoreaction of 4,5',8-trimethylpsoralen (TMP) with adenosine was investigated in a dry film state. Four major photoadducts were isolated and purified by reverse-phase liquid chromatography. The structures of the photoproducts were elucidated on the basis of spectroscopic methods, including UV, FT-IR, mass spectrometry (FAB and EI methods) and 1H-NMR analysis. These photoproducts were characterized to be TMP-adenosine 1:1 adducts, which resulted from the covalent bond formation between the carbon C(4) of TMP and ribose 1' or 5' carbon of adenosine. Of the photoadducts, one photoadduct (V) was the major product, reflecting some selectivity in the photoreaction of TMP with adenosine in the solid state.

Abstract— The photodimerization of 4,5'.8‐trimethylpsoralen(TMP) in dichloromethane solution has been investigated. Three products have been isolated and characterized: (1) a non‐fluorescent homodi‐mer resulting from the C4‐cycloaddition at the pyrone end, with a trans‐anti configuration, (2) a bicyclomer resulting from a double cycloaddition between pyrone and furan moieties, and (3) a fluorescent heterodimer resulting from the C4‐cycloaddition between the furan end of one TMP moiety and the pyrone end of the other, with cis‐syn configuration.

A novel photoadduct of 4,5',8-trimethylpsoralen (TMP) and adenosine was isolated and purified by reverse-phase liquid chromatography. The structure of the photoproduct was determined by various spectral methods and found to be a TMP-adenosine 1:1 adduct resulting from the covalent bond formation between the carbon C(4) of TMP and ribose 4'-carbon of adenosine.

Irradiation of thin films consisting of 4,5',8-trimethylpsoralen (TMP), adenosine and small amounts of alcohols led to TMP-alcohol photoadducts in addition to TMP-adenosine photoadducts. Four TMP-ethanol and two TMP-methanol adducts have been separated and characterized. Covalent bonds were formed between the 4-carbon of TMP and the alpha-carbon to the hydroxy group in the alcohols. The TMP-alcohol photoadducts were formed only in the TMP film containing small amounts of alcohol and adenosine. Furthermore, no photoadduct of TMP and ribose was detected upon photolysis of a TMP-ribose film, suggesting that the adenine moiety plays a specific role in the reaction. The interaction of adenosine with psoralens in a dry film may be related to the DNA sequence selectivity observed for the photoreaction of psoralens with DNA.