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