Elongatin (4′,5-dihydroxy-2′,5′-dimethoxy-2″,2″-dimethylpyrano[5″,6″-g]isoflavone) was synthesized by an oxidative rearrangement of the corresponding pyronochalcone [6-(1-oxo-3-phenyl-2-propenyl)-4-chromanone] with thallium(III) nitrate and a regioselective reduction of 7-(4-benzoyloxy-2,5-dimethoxyphenyl)-2,3-dihydro-2,2-dimethyl-5-tosyloxy-4H,6H-benzo[1,2-b:5,4-b′]dipyran-4,6-dione with sodium boronydride–palladium chloride, followed by dehydration of the resultant alcohol and hydrolysis. Its angular isomer (4′,5-dihydroxy-2′,5′-dimethoxy-2″,2″-dimethylpyrano[6″,5″-h]isoflavone) was also synthesized from the corresponding pyronochalcone in a similar manner.

Much attention has been paid to water-soluble porphyrins and metalloporphyrins as potential sensitizers for photodynamic therapy (PDT). Thus, water-soluble tricationic phosphorus porphyrin complexes were prepared via the introduction of an N-alkylpyridinio group on the axial ligands of phosphorus porphyrins. The resulting tricationic phosphorus porphyrins readily dissolve in aqueous solutions without the formation of aggregates, even at high concentration. Moreover, the affinity of the porphyrins to human serum albumin (HSA) is a key factor in their application to PDT since HSA plays an important role in the transport of drug molecules to a target cell. Interactions between the tricationic phosphorus porphyrins and HSA were examined on the basis of changes in the Soret bands of the absorption and fluorescence spectra of phosphorus porphyrin solutions in the presence of HSA and the fluorescence quenching of HSA by the tricationic phosphorus porphyrins. Tricationic phosphorus porphyrins with moderately long alkyl chains on the pyridinio group were strongly adsorbed on the HSA at a position near the tryptophan residue of HSA. This result suggests that tricationic phosphorus porphyrins containing alkyl groups are good candidates as PDT reagents because of their high water solubility and high affinity for HSA.Much attention has been paid to porphyrins and metalloporphyrins because of their potential for use as sensitizers for photosterilization 1,2 and photodynamic therapy (PDT). 36 In general, photosensitizers used in clinical applications should meet the following requirements: i) sufficient solubility in water for handling in aqueous media, ii) strong absorption at longer wavelengths in the visible region, iii) the capability to generate active oxygen species, such as singlet oxygen, via energy transfer from the triplet state of the sensitizer and/or to directly oxidize tumor cells via photoinduced electron transfer, 7,8 and iv) adsorption on the plasma proteins, such as albumin, hemoglobin, and lipoproteins, which carry sensitizers to tumor cells.911 Among these proteins, we focused on human serum albumin (HSA), which is the most abundant plasma protein, since HSA has the ability to bind many kinds of drugs 12,13 and is applied to drug delivery systems.14 In general, water solubilization of porphyrins has been achieved through the introduction of ionic groups such as pyridinium, 7,1518 sulfonate, 1921 and phosphonium 18,22 in the porphyrin rings. However, despite the presence of such ionic groups, many types of water-soluble porphyrins tend to form face-to-face aggregates, resulting in low water solubility in buffer and saline solutions. 17,22,23 To prevent this face-to-face interaction, we have examined water solubilization via modification of the axial ligands of antimony-and phosphoruscontaining porphyrins. 2428 Recently, we prepared watersoluble phosphorus porphyrins bearing axial ligands, such as hydrophilic ethyleneoxy and/or hydrophobic alkoxy groups. 27,28 However, the presence of other components such...

We examined photochemical effects by ultraviolet irradiation on facilitated proton transfer at a water/1,2-dichloroethane (W/DCE) interface by ion-transfer voltammetry using a Xe flash lamp. 5,10,15,20-Tetraphenyl-21H,23H-porphine (HTPP) or its metal complex, such as cobalt (Co(II)TPP), zinc (Zn(II)TPP), and nickel (Ni(II)TPP) complexes, was added into the DCE phase as an ionophore for the facilitated proton transfer. After we irradiated the W/DCE interface through the W phase, the voltammetric waves for proton transfer facilitated by HTPP and Co(II)TPP were remarkably enhanced and shifted to the lower potential region, compared to those before irradiation. We confirmed from the pH and argentometric titrations that such enhancements and shifts of the waves were caused by hydrogen chloride (HCl) produced by photodecomposition of DCE. On the other hand, the waves for proton transfer facilitated by Zn(II)TPP and Ni(II)TPP were very small from the beginning, and showed neither enhancement nor any shift upon irradiation.

No abstract

Review: 37 refs.