Synthesis and characterization of new methylpsoralens as potential photochemotherapeutic agents.

Three new psoralens with methyl groups on carbons involved in their reactive double bonds (compounds 9-11 in Scheme 1) were synthesized from the corresponding 7-hydroxycoumarins by cyclization of acetonyl derivatives of the latter in an alkaline medium. In preliminary tests, the new methyl-substituted psoralens exhibited considerable interaction in the dark with DNA, good photoreactivity against the macromolecule, and also interesting antiproliferative activity.