Hydrogen Transfer And Solvent Effect. New Light-induced Molecular Biologically Active Substances

The intramolecular pronton transfer (IPT) of a novel type of perylenequinonoidphotosensitizer (PQP)--Hypomycin A (HMA) have been investigated employingquantum chemistry method to shed light on the IPT mechanisms of PQP. The solventeffect of hypocrellin B and naphthazarin, together with different substituted molecules,have also been studied.The quality of photosensitizer is a key factor for the efficiency of photodynamictherapy (PDT). In recent years, much research attention has been focused on a noveltype of photosensitizer, perylenequinonoid derivatives (PQD). Experimentalevidences have suggested that PQD have the potential to replace Photofrin Ⅱas thelatest photodynamic medicine.Recently, a new novel type of photosensitize-hypomycin A (HMA) was isolated fromthe mycelia of Hypomyces sp.. Similar to the structure of typical PQP, HMA has ahydroxyl group peri to a carbonyl group at each end, but its structural skeleton isdifferent in that the bond of C11-C12 is single rather than double. Therefore, theenvironment around the transferable hydrogen at both sides is different so that the IPTprocess of H14 and H17 may be distinguishable by theoretical calculation. Moreover,the two IPT fashions of HMA facilitate making clear the role of two transferablehydrogens as well as the structural effect on IPT process.Employing the ab initio, CIS methods in the Gaussian 98 package programs, we firstlyinvestigated the different IPT processes of HMA and discussed the IPT mechanisms ofPQP. The solvent effect of the HB and naphthazarin, together with different substitutedmolecules were also studied. The results may be invoked to direct the experiment tosynthesize new type of excellent photosensitizers and select the better solvents.The most important results are as follows:i. According to the calculated results for HMA, it was revealed firstly, the IPT barriersof the underside(60.70kJ/mol) got approximately 18.37kJ/mol higher than the upperbarriers(42.33kJ/mol). Secondly, the potential energy surface of the singlet and tripletexcited state were disjunct, which was different with the other PQP. So we spelculated...