An improved large scale synthesis of 1,4-anhydro-4-thio-d-ribitol

An improved large scale synthesis of 1,4-anhydro-4-thio-d-ribitol (4) from d-ribose has been accomplished by combining the O-allyl and O-p-methoxybenzyl protecting groups. Compound 4 was obtained in 31% yield in eight steps with three chromatographic separations.     

Long-lived charge-separated state leading to DNA damage through hole transfer

The hole transfer causes the long-lived charge-separated state in DNA during the photosensitized one-electron oxidation of DNA. The combination of the transient absorption measurement and DNA damage quantification by HPLC clearly demonstrated that the yield of the DNA damage correlates well with the lifetime of the charge-separated state.     

Eine quantitative Bestimmung von Chinonen

Ohne Zusammenfassung     

Photophysical properties of Zn-substituted cytochrome c investigated by single-molecule and ensemble-averaged spectroscopy

The study of the structural reorganization and photophysical properties of Zn-Cytc using the single-molecule and ensemble-averaged spectroscopy shows that the photoblinking behaviors of single-Zn-Cytc depend on the folded and unfolded structures, whereas the fluorescence dynamics of Zn-Cytc observed in the bulk phase are hardly affected by the conformational change of a protein.     

Synthesis and characterization of hollow ��-Fe2O3 sub-micron spheres prepared by sol�Cgel

In this work we report the preparation of magnetic hematite hollow sub-micron spheres (??-Fe₂O₃) by colloidal suspensions of ferric nitrate nine-hydrate (Fe(NO₃)₃·9H₂O) particles in citric acid solution by following the sol?Cgel method. After the gel formation, the samples were annealed at different temperatures in an oxidizing atmosphere. Annealing at 180°C resulted in an amorphous phase, without iron oxide formation. Annealing at 250°C resulted in coexisting phases of hematite, maghemite and magnetite, whereas at 400°C, only hematite and maghemite were found. Pure hematite hollow sub-micron spheres with porous shells were formed after annealing at 600°C. The characterization was performed by X-ray diffraction (XRD), Mössbauer spectroscopy (MS) and scanning electron microscopy (SEM).     

Comparisons of O-acylation and Friedel-Crafts acylation of phenols and acyl chlorides and Fries rearrangement of phenyl esters in trifluoromethanesulfonic acid: effective synthesis of optically active homotyrosines

Reactions involving phenol derivatives and acyl chlorides have to be controlled for competitive O-acylations and C-acylations (Friedel-Crafts acylations and Fries rearrangements) in acidic condition. The extent for these reactions in trifluoromethanesulfonic acid (TfOH), which is used as catalyst and solvent, is examined. Although diluted TfOH was needed for effective O-acylation, concentrated TfOH was required for effective C-acylations in mild condition. These results have been applied to the novel synthesis of homotyrosine derivatives. Both Fries rearrangement of N-TFA-Asp(OBn)-OMe and Friedel-Crafts acylation of phenol with N-TFA-Asp(Cl)-OMe in TfOH afforded the homotyrosine skeleton, followed by reduction and deprotection afforded homotyrosines maintaining stereochemistry of Asp as an optically pure form.     

A new method for the stereoselective construction of angular methyl group of fuzed cyclic ethers

A convenient method for the stereoselective construction of angular methyl group of fuzed cyclic ethers is described. Reactions of mixed thioacetals with Me₂Zn/Zn(OTf)₂ afforded the corresponding methylated products in good yields. Various protective groups such as MOM ether, benzylidene acetal, TBS ether, and pivaloyl group were stable under the reaction conditions.     

Photoisomerization of 2′-deoxyribofuranosyl and ribofuranosyl 2-phenylazoimidazole

Novel photo responsive nucleosides, 1-N-(2′-deoxyribofuranosyl) 2-phenylazoimidazole and 1-N-ribofuranosyl 2-phenylazoimidazole have been designed and synthesized. trans-cis Photoisomerizations of the nucleosides with irradiation at a specific wavelength have been observed and the isomerizations are perfectly reversible.