THE C4‐PHOTOCYCLODIMERS OF 4,5',8‐TRIMETHYLPSORALEN(TMP)

Abstract— The photodimerization of 4,5'.8‐trimethylpsoralen(TMP) in dichloromethane solution has been investigated. Three products have been isolated and characterized: (1) a non‐fluorescent homodi‐mer resulting from the C 4 ‐cycloaddition at the pyrone end, with a trans‐anti configuration, (2) a bicyclomer resulting from a double cycloaddition between pyrone and furan moieties, and (3) a fluorescent heterodimer resulting from the C 4 ‐cycloaddition between the furan end of one TMP moiety and the pyrone end of the other, with cis‐syn configuration.