Difurocoumarins: Psoralen analogs as photochemotherapeutic agents

New tetracyclic psoralen-like compounds have been synthesized, which are characterized by two furan rings angularly condensed on the coumarin nucleus and are therefore called difurocoumarins. This structural feature may favour the intercalation into the DNA helix and then monofunctionally photoreaction with DNA bases. Their synthesis started from 5,7-dihydroxy-4-methylcoumarin, which was condensed with alpha -haloketones; the resulting ketoethers were then cyclized to give the title compounds