Synthesis and photobiological properties of 4- hydroxymethyl-4'- methylpsoralen derivatives.

The synthesis and photobiological properties of two new hydroxymethylpsoralen derivatives of psoralens namely 4- hydroxymethy-4'-methyl and 4- hydroxymethyl-8-methoxypsoralen are described. Both compounds exhibited efficient photobinding to DNA and RNA. The DNA-photobinding process was investigated using different nucleic acid structures such as double-helical DNA, ribosomal DNA, bacterial DNA and DNA organized in the nucleosomal arrangement. The test derivatives were able to induce cross-links to a similar extent as 8-methoxypsoralen (8-MOP), used as a reference photochemotherapeutic drug. In contrast to 8-MOP, they produce relatively high level of singlet oxygen. Most photobiological effects showed a good correlation with the extent of covalent photoaddition........