Synthesis of [7-14C]bergapten

Bergapten (1) is a furocoumarin natural product and currently employed to treat skin disorders. Since past attempts to radiolabel 1 with C-14 were limited to only its 5-methoxy group, a synthesis of the required ring [7-C-14]1 is now described. The literature reported precursor 4-methoxy-6-hydroxybenzofuran-5-carboxaldehyde (3) was Wittig reacted with stabilized [carbonyl-C-14]methoxycarbonylmethylenetriphenylphosphorane (4) to obtain [7-C-14]1 in 47% radiochemical yield, with the desired product being characterized by thin-layer chromatography, HPLC, m.p. and proton NMR.