Catalytic Asymmetric Epoxidation of α,β‐Unsaturated Esters with Chiral Yttrium–Biaryldiol Complexes

The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)₃–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)₃–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent.     

Synthetic polymers adsorbing bisphenol A and its analogues prepared by covalent molecular imprinting using bisphenol A dimethacrylate as a template molecule

Synthetic polymers which can adsorb bisphenol A (BPA) and related compounds were prepared by a covalent molecular imprinting technique. BPA dimethacrylate, used as template molecule, was polymerized with a crosslinker, triethylene glycol dimethacrylate (TEGDMA) or trimethylol propane trimethacrylate (TRIM). After the polymerization treatment with dilute NaOH was used to cleave BPA from the polymers. For high recovery of BPA with low polymer matrix degradation, the hydrolysis conditions were determined to be treatment with 1.0 mol L^–1 NaOH for 48 h. The binding sites generated by the hydrolysis were evaluated by determination of the retentivity of BPA, BPA analogues, and other endocrine disruptors. The polymers strongly adsorbed compounds with two hydroxyl groups at the 4,4-positions. Generally the TEGDMA-based polymers had stronger affinity than the TRIM-based polymers, although the TRIM-based polymer adsorbed steroidal hormones with two hydroxyl groups, for example 17-estradiol and 17-estradiol, more strongly than the TEGDMA-based polymer, meaning that the crosslinkers affected the properties of the binding sites and, depending upon the target molecules, suitable crosslinkers should be chosen in this system.     

New types of Br?nsted acid-base ionic liquids-based membranes for applications in PEMFCs.

A series of ionic liquids (ILs) are prepared by neutralizing tertiary amines with N,N-bis(trifluoromethanesulfonyl)imide (HTFSI). As demonstrated by thermal and electrochemical characterizations, these ILs have very good temperature stability and a high ionic conductivity, that is, of the order of 10(-2) S cm-1. By incorporating these ILs into a poly(vinylidenfluoride-co-hexafluoropropylene) polymer matrix, membranes with a high melting temperature, high decomposition point and with an ionic conductivity of about 10(-2) S cm-1 at 140 degrees C, are obtained. These IL-based, proton-conducting membranes are proposed as new polymer electrolytes for high-temperature polymer electrolyte membrane fuel cells (PEMFCs).     

Matrix metalloproteinases in lung diseases

Matrix metalloproteinases (MMPs) are a pivotal family of zinc enzymes responsible for degradation of the extracellular matrix (ECM) components including basement membrane collagen, interstitial collagen, fibronectin, and various proteoglycans, during normal remodeling and repair processes. The potent proteolytic activities of MMPs is mainly regulated by the balance with specific tissue inhibitors of Matrix metalloproteinases (TIMP). Excessive or inappropriate expression of MMP may contribute to the pathogenesis of tissue destructive processes in a wide variety of diseases including lung diseases. Although the precise mechanisms are still unknown, the contribution of individual MMPs are worth investigating in seeking the pathogenesis of various lung diseases such as lung cancer, bronchial asthma, chronic obstructive pulmonary disease, acute lung injury, pulmonary hypertension and interstitial lung diseases. In particular, the close association of each lung disease with the destructive effects of gelatinase A and B (also called MMP-2 and MMP-9) on the basement membrane in early alveolar remodeling, and that of collagenase-1 (MMP-1) on the major interstitial structural protein of ECM have received considerable attention. The interaction of MMPs with chemical mediators and inflammatory cytokines has also been reported in some recent studies. Several promising therapeutic approaches to inhibit MMPs have just started in the field of oncology, while more specific MMP inhibitors may be required for further investigation in other fields of lung diseases. In this review, the main focus is on the recent clinical and experimental findings and the contributions of MMPs and/or TIMPs in the lung diseases.     

Ladderlike ferromagnetic spin coupling network on a pi-conjugated pendant polyradical

A poly(9,10-anthryleneethynylene)-based polyradical with two pendant stable phenoxyls in one anthracene skeleton was newly synthesized via polymerization of the corresponding bromoethynylanthracene monomer using a Pd(0) catalyst. The average molecular weight of the polymer reached M(n) = 5 x 10(3) and was soluble in common organic solvents. The polyradical was prepared from the corresponding hydroxyl precursor polymer and was appropriately stable at room temperature. The ESR spectrum of the corresponding monomeric radical suggested an effectively delocalized spin density distribution on the backbone anthracene. The magnetization and the static magnetic susceptibility of the polyradical were measured using a SQUID magnetometer. The large average spin quantum number (S = (5)/(2)) of the polyradical indicated that the ferromagnetic spin coupling network of the polyradical had spread throughout the pi-conjugated chain and that it was considerably insensitive to spin defects.     

Structural scaffold of 18-crown-6 tetracarboxylic acid for optical resolution of chiral amino acid: X-ray crystal analyses and energy calculations of complexes of D- and L-isomers of tyrosine, isoleucine, methionine and phenylglycine

To clarify the structural scaffold of (+)-18-crown-6 tetracarboxylic acid ((+)-18C6H4) for the optical resolution of a chiral amino acid, the crystal structures of its equimolar complexes with L- and D-isomers of tyrosine (Tyr), isoleucine (Ile), methionine (Met) and phenylglycine (PheG) were analysed by X-ray diffraction methods. (+)-18C6H4 took very similar conformations for all complexes. Although the chemical structure of (+)-18C6H4 is C2-symmetric, it took a similar asymmetric ring conformation of radius ca. 6.0 A. In all complexes, the amino group of chiral amino acids was located near the center of the ring and formed three hydrogen bonds and five electrostatic interactions with eight oxygen atoms of the ether ring and carboxyl groups. Also, the Calpha atom of chiral amino acids participated in Calpha-H...O interaction with the oxygen atom of (+)-18C6H4. In contrast, the carboxyl group of chiral amino acids did not directly interact with (+)-18C6H4. These results indicate that the structural scaffold of (+)-18C6H4 for the optical resolution of chiral amino acids is mainly based on the mode of interaction of (+)-18C6H4 with the amino and Calpha-H groups of chiral amino acids. The differences in interaction pattern and binding energy between the L- and D-isomers of each amino acid are discussed in relation to the chiral recognition of (+)-18C6H4.     

Crystal and solution structures of photochromic spirobenzothiopyran. First full characterization of the meta-stable colored species.

Full elucidation for stable, colorless, and meta-stable colored structures of a new spirobenzothiopyran has been achieved both in the solid state and in a solution. 1',3',3'-Trimethyl-6-nitrospiro[(2H)-1-benzothiopyran-2,2'-indoline] with an ester group as a substituent at the 8-position of 1-sp shows photochromism. The blue-green colored species resulted from UV irradiation (365 nm) in one minute and spontaneously bleaches within one minute in acetone and methanol at 27 degrees C. UV exposure (365 nm) of 1-sp in methanol for 3 h at room temperature results in the growth of deep blue needlelike single crystals of the open form of spirobenzothiopyran, photomerocyanine 1-pmc, whose structures in the solid state and in solution were obtained unambiguously. The X-ray structural analysis of 1-pmc revealed the molecular structure of the zwitterionic photomerocyanine with s-trans,s-trans conformation. 1-pmc is soluble to polar solvents and thermally returns to 1-sp. In the DMSO solution, 1-pmc is found to return slowly to 1-sp (1-pmc gave only 18% of 1-sp for 30 min at 22 degrees C). The detailed NMR studies in DMSO-d(6) including COSY and NOE techniques as well as isotope labeling of the compound showed the structure with s-trans,s-cis conformation in a solution.     

Measurement of bisphenol A in human serum by gas chromatography/mass spectrometry

The purpose of this study is to establish an easy and accurate method for the determination of bisphenol A (BPA) in the human serum. The samples were applied to the C₁₈ solid phase extraction (SPE) column for clean up of samples. The BPA is conjugated with tetrabutylammonium hydrogen sulfate as the counter ion in alkali solution. The ion paired BPA is moves from the aqueous phase to the organic phase as an ion paired extraction. BPA extracted from human serum were derivatized with pentafluorobenzyl bromide (PFBBr). The derivative was analyzed by gas chromatography (GC)/mass spectrometry (MS) using negative chemical ionization (NCI). The instrumental detection limit of BPA was 5 pg/ml (10 fg). The instrumental response between 0.01 and 100 pg/ml of BPA standards was linear (r²=0.998). The recovery of BPA spiked into human serum was 101.0±4.63 (1 pg/ml) and 100.9±3.75 (10 pg/ml), respectively. The concentration of BPA in the human serum from 20 individuals was 0.54 pg/ml.     

Measurement of 4-nonylphenol and 4-tert-octylphenol in human urine by column-switching liquid chromatography-mass spectrometry

We report a method for determining 4-nonylphenol (NP) and 4-tert-octylphenol (OP) levels in human urine samples by column-switching liquid chromatography-electrospray mass spectrometry after enzymatic deglucuronidation. The method involves enzymatic deconjugation by β-glucuronidase and correction by the stable isotopically labeled internal standard, 4-(1-methyl)octylphenol-d₅. The compounds were separated by reversed-phase chromatography with a C₁₈ column, and detected by selected ion monitoring in the negative mode. After adding an internal standard to urine samples, a direct analysis was carried out. The average recoveries of OP and NP were above 85.0% with correction using the added internal standard. The quantitation limit in the urine samples was 0.3 ng ml⁻¹. The method enables the precise determination of standards and may be applied to the detection of trace amounts of OP and NP in human urine samples.     

Carboxymethyl poly(L‐histidine) as a new pH‐sensitive polypeptide at endosomal/lysosomal pH

A carboxymethyl poly(L ‐histidine) has been synthesized as a new pH‐sensitive polypeptide at endosomal/lysosomal pH. Because of its poor water solubility at physiological pH, an application of poly(L ‐histidine) with a pK_a around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the unmodified poly(L ‐histidine) suddenly precipitates out of the aqueous medium above pH 6.0 as the result of the deprotonation of the imidazole groups, the water solubility of the resulting carboxymethyl poly(L ‐histidine) has been improved at physiological pH. A solution turbidity measurement proved that no significant effect on a rapid aggregate formation or phase separation of serum proteins is induced by carboxymethyl poly(L ‐histidine). Hemolysis assay showed that the carboxymethyl poly(L ‐histidine) enhances membrane disruptive ability at endosomal/lysosomal pH. The cellular uptake of luciferase in the presence of the carboxymethyl poly(L ‐histidine) increases intracellular luciferase activity, which suggests that the carboxymethyl poly(L ‐histidine) makes the luciferase escape from lysosomal degradation. The carboxymethyl poly(L ‐histidine) would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal/lysosomal pH. Copyright © 2007 John Wiley & Sons, Ltd.