Effect of titanium dioxide on photostability of solid-state mequitazine

TiO(2) has been widely used in pharmaceutical products, and it also has been used as a photocatalyst. In this study, the influence of photocatalytic activity on the stability of solid-state mequitazine, an H(1)-blocker, was investigated. The photo-degradation of mequitazine with TiO(2) occurred under irradiation with both light sources. The degree of degradation of mequitazine with anatase was higher than that of rutile. The degradation was significantly enhanced with increasing relative humidity. The relationship between the apparent degradation rate constant and water vapor pressure could be clearly described by a simple power law. The major photo-degradation products of mequitazine, resulting from photocatalytic activity of TiO(2), were mequitazine-S-oxide and mequitazine-sulphone. A remarkable degradation of mequitadine occurred with addition of TiO(2), and its photocatalytic activity was controlled by water vapor pressure. The photo-degradation of mequitazine with TiO(2) is a different process from mequitazine without TiO(2), because mequitazine-S-oxide and mequitazine-sulphone are not formed with normal photo-degradation of mequitazine.     

Rapid ruthenium-catalyzed synthesis of pyranopyrandiones by reconstructive carbonylation of cyclopropenones involving C[bond]C bond cleavage

Pyranopyrandiones were prepared by a novel ruthenium-catalyzed carbonylative dimerization of cyclopropenones via C-C bond cleavage. For example, treatment of dipropylcyclopropenone with a catalytic amount of Ru3(CO)12 and NEt3 in THF under 15 atm of carbon monoxide at 140 degrees C for 20 h gave a novel functional monomer, 3,4,7,8-tetrapropylpyrano[6,5-e]pyran-2,6-dione, in an isolated yield of 81%. Unsymmetrically substituted pyranopyrandiones were also obtained by ruthenium-catalyzed carbonylative coupling of cyclopropenones with alkynes under similar reaction conditions.     

Trifluoromethylated amino alcohols as chiral ligands for highly enantioselective Reformatsky reaction

The enantioselective Reformatsky reaction of PhCHO was achieved by the use of trifluoromethylated amino alcohols as chiral ligands to afford the corresponding optically active β-hydroxy ester with up to 90% ee.     

Polycyclic N-hetero compounds. XXVII. Synthesis and investigation of the antidepressive activity of a B-Homo-11,13,15-triazasteroid and its related compoundsd

A synthesis of 1,2,5,6-tetrahydro-4H-benzo[3,4]cyclohepta[1,2-e]imidazo[1,2-c]pyrimidine (XII) having a novel ring system is described. Antidepressive activity of XII and its precursors VII-X was screened by inhibitory action of reserpine-induced hypothermia.     

Synthesis,surface accumulation,and micellar properties of amphiphilic block copolymers

Amphiphilic block copolymers, i.e., poly(methyl methacrylate)-b-poly(2-dimethylethylammoniumethyl methacrylate), were synthesized by the reaction between two prepolymers. Carboxyl-terminated poly(methyl methacrylate) and hydroxyl-terminated poly(2-dimethylaminoethyl methacrylate) were prepared by radical polymerization of the corresponding monomers in the presence of thioglycolic acid and 2-mercaptoethanol as a chain transfer agent, respectively. Two condensation methods, i.e., DCC and the acid chloride method, were used for the reactions of these prepolymers. The subsequent quarternization produced the amphiphilic block copolymers. Surface property of poly(methyl methacrylate) films containing this amphiphilic block copolymer was examined by measuring contact angles for water. The addition of only 0.5 wt% of the block copolymer was sufficient to make poly(methyl methacrylate) surfaces hydrophilic. The block copolymer formed a polymeric micelle in acetone–water mixed solvent.     

Helical pitch of m-phenylene ethynylene foldamers by double spin labeling

To investigate the helical conformation of oligo(m-phenylene ethynylene)s, a pair of TEMPO spin labels were appended to the backbone. The two TEMPO radicals were separated by the four, five, and six repeating units. ESR spectra of the labeled oligomers were measured in chloroform and in ethyl acetate solvents in which the oligomers are disordered and folded, respectively. The measurement and analysis of ESR spectra revealed that six repeating units make one helical turn.     

Studies directed towards the asymmetric total synthesis of antileukemic lignan lactones. Synthesis of optically pure key intermediate and its utility

By the self-immolative asymmetric synthesis, optically pure key intermediate β-piperonyl-γ-lactone (R)-(+)-$\text{6}$ was found to be prepared in reasonable yield from the easily available chiral γ-lactone synthon ($\text{1}$) which had been also reported to give an antipode (S)-(-)-$\text{6}$. The optically pure (R)-(+)-$\text{6}$ was shown to be converted successfully into several optically pure natural lignan lactones.     

Optimization of matrix-assisted laser desorption/ionization time-of-flight collision-induced dissociation using poly(ethylene glycol)

Details of the optimization of the collision-induced dissociation (CID) process, using a collision cell on a matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometer, are described using poly(ethylene glycol) 1000 (PEG 1000) as a model analyte. The effects of collision gas identity (helium, air, and argon), as well as collision gas pressure, on the resulting MS/MS data were investigated. With PEG 1000, helium was found to give the best results with respect to signal-to-noise (S/N) ratio. The optimum pressure for each gas was found to be in the range where the precursor ion signal was attenuated to approximately 30-50% for helium and 40-60% for argon. The effect of cation choice (Li, Na, and K) on the CID of PEG was also studied. CID spectra were produced for each, but PEG cationized with lithium was found to produce the spectra with the highest S/N ratio. The MALDI-TOF CID spectra that were generated for PEG were compared with the high-energy and low-energy MS/MS spectra obtained from a sector mass spectrometer and from a triple quadrupole mass spectrometer, respectively. The results observed for PEG confirm that CID on a MALDI-TOF mass spectrometer is a high-energy MS/MS technique.     

First asymmetric total synthesis of (+)-steganacin determination of absolute stereochemistry

(+)-Steganacin was synthesized in a new and highly specific asymmetric pathway based on the novel application of chiral γ-lactone as a chiral synthon. By this synthesis the absolute stereochemistry of natural (?)-steganacin could be determined in unequivocal way.     

Effects of catechins on superoxide and hydroxyl radical

Superoxide (O2-.) was reduced by the addition of superoxide dismutase (SOD: O2-. scavenger) and catechins. In competitive reactions utilizing different concentrations of spin-trap agent, the IC50 values of each sample were changed. With regard to the Cu2+/H2O2 and Fe2+/H2O2 reaction systems, metal chelater, hydroxyl radical (.OH) scavenger and catechins eliminated the levels of .OH. For the Cu2+/H2O2 reaction systems, the IC50 for .OH scavenger changed, but that for metal chelater and catechins did not. However, for the Fe2+/H2O2 reaction system, the IC50 for .OH scavenger and catechins changed, whereas that for metal chelater did not. The ESR signal for free Cu2+ was changed by addition of metal chelater and catechins. In the spectrophotometer experiments, it was confirmed that the CuCl2 spectrum was changed by addition of metal chelater and catechins but not by .OH scavenger. Conversely, the FeSO4 spectrum was not changed by addition of .OH scavenger or catechins, but was altered by metal chelater. Lipid peroxidation was inhibited by catechins in a concentration-dependent manner. Therefore, it was suggested that the catechins did not scavenge directly the generated .OH from the Cu2+/H2O2 reaction system, but inhibited the generation of .OH by acting on the Cu2+/H2O2 reaction system. On the other hand, with respect to the .OH generated from the Fe2+/H2O2 reaction system, it was suggested that the catechins had a direct scavenging capacity of the .OH, but had little chelating activity of iron. It was confirmed that catechins have the ability to scavenge for O2-. as well as .OH and to inhibit the generation of .OH by chelation with metal ions.