The C4‐photocyclodimers of 4,5',8‐trimethylpsoralen(tmp)

Abstract

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 C4‐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 C4‐cycloaddition between the furan end of one TMP moiety and the pyrone end of the other, with cis‐syn configuration.

Furocoumarin photolysis: chemical and biological aspects

“…The most potent among the set of molecules tested is tucaresol (63). 53 Independently of the immunological aspects, which cannot be evaluated in this review, it is intriguing to note that tucaresol is an o-hydroxybenzaldehyde, just as some of the abovedescribed psoralen photoproducts are (22,23,27,29,30). Thus, it is reasonable to expect that some photoproducts of psoralens, if formed in vivo, may play a role in the regulation of the immune system.…”

“…The work by Shim et al 30 deserves special consideration. By irradiating 4,5Ј,8-trimethylpsoralen (TMP), the authors isolated a pyrone-pyrone dimer (16) which, in agreement with Krauch's work on 8-MOP, 23 was assigned the trans-anti configuration by means of NMR experiments carried out in the presence of shift reagents.…”

Photo Reaction of 4,5‘,8‐trimethylpsoralen With Adenosine

“…This is further confirmed by the observation of two doublets having a geminal coupling constant (2J = -15.9 Hz) at 2.48 and 3.20 ppm in the 'H-NMR spectra of the adduct V, which are assigned as two methylene protons of dihydropyrone in the TMP moiety. This pattern arose only in the C(4) coupled structure; in the C(3) coupled structure the 4-H of dihydropyrone ring would have a vicinal coupling with both 3-H and 4-methyl protons, resulting in a complex multiplet as is shown in 'H-NMR spectrum of tetrahydro-4,5',8-trimethylpsoralen (Shim et al, 1990). The other two methyl resonances were shifted slightly upfield with respect to those of TMP.…”

“…Hydrophilic adenosine was eluted first followed by five photoproduct peaks and then the less polar TMP appeared. These five product peaks are labeled I, 11, 111, IV and V. The three slowest eluting peaks at 28, 29, and 31.5 min were assigned as (2+2) TMP photocyclodimers on the basis of photoreversion experiments with 254 nm UV light and also by comparing the retention behavior with authentic compounds which had been prepared previously in this laboratory (Shim et a / . , 1990).…”

Reversible Photocycloaddition of a 4′,5′‐dihydropsoralen Derivative With Thymine

“…In the literature such upfield shifts have been described, e.g. for the dimers of 8-MOP and 4',5'dihydro-8-MOP derivatives (Gervais and De Schryver, 1975) and dimers of 4,5',8-trimethylpsoralen (Shim et al, 1990). The authors have assigned an endo configuration for these photodimers whereas they have proposed an ex0 configuration for the photodimers which do not present this effect.…”