Stereoregularity of poly(methyl α-chloroacrylate)

Triad and tetrad tacticities of poly(methyl α-chloroacrylate) and poly(methyl α-chloroacrylate-β-d₁) were determined by nuclear magnetic resonance (NMR) spectroscopy. Methyl α-chloroacrylate-β-d₁ and its polymer were first synthesized. Isotactic poly(methyl α-chloroacrylate) was prepared with ethylmagnesium chloride-benzal-acetophenone in combination as catalyst. The syndiotacticity of radically polymerized polymers increased with decreasing polymerization temperature. For radical polymerization, enthalpy and entropy differences between isotactic and syndiotactic additions were calculated to give ΔH ? ΔH = 850 cal/mole and ΔS ? ΔS = 0.93 eu. The stereoregularity of the polymer prepared with phenylmagnesium bromide catalyst was analyzed in fairly good agreement with first-order Markov statistics, while polymerization with fluorenyllithium seems predominantly to proceed by a mechanism similar to free-radical mechanism. Stereoregularity-controlling power for individual substituents is briefly discussed.     

The intercalation of metalloporphyrin complex anions into layered double hydroxides

Investigations to elucidate the structures of the cobalt(III) and manganese(III) complexes of tetra(p-sulfonatophenyl)porphinate anions (M(III)TSPP; M = Co and Mn), intercalated in Mg-Fe/Cl and Mg-Al/Cl layered double hydroxides (LDHs) have been carried out. Powder X-ray diffraction analysis, IR and UV-vis diffuse reflectance spectroscopy of Co(III)TSPP and Mn(III)TSPP intercalated into the interlayer spaces of LDH resulted in their perpendicular alignment against the host layers in the plane of the hybrid.     

Resistance of zwitterionic telomers accumulated on metal surfaces against nonspecific adsorption of proteins

Telomers of N,N-dimethyl-N-(3-sulfopropyl)-3'-methacryloylaminopropanaminium inner salt (SPB), 2-methacryloyloxyethyl phosphorylcholine (MPC), and N,N-dimethyl-N-(1-carboxymethyl)-2'-methacryloyloxylethanaminium inner salt (CMB) were prepared by UV irradiation in the presence of N,N,N',N'-tetraethylthiuram disulfide and a disulfide-group-carrying iniferter (a compound which pursues initiation, chain transfer, and termination), Cys-BDC, which had been prepared by coupling N,N-diethyldithiocarbamoylmethylbenzoic acid succinimidyl ester with cystamine dihydrochloride. The telomers formed a self-assembled monolayer (SAM) on a gold electrode and a monolayer of colloidal gold deposited on a glass plate, as confirmed by the increase in potential difference (DeltaE(p)) of the voltammogram for hydroquinone as a probe using cyclic voltammetry (CV) and the increase in absorbance using localized surface plasmon resonance (LSPR) absorption spectroscopy, respectively. Nonspecific adsorption of various proteins onto the surfaces of various telomer SAMs was examined from the decrease in peak current (DeltaI) using CV and the absorption increase at 550 nm using LSPR absorption spectroscopy. The zwitterionic telomer SAM in general did not adsorb proteins significantly, suggesting the usability of zwitterionic polymer SAMs and brushes to coat various materials used in biomedical fields. The correlation between the structure of water in the vicinity of zwitterionic telomers and the resistance of the zwitterionic telomer SAMs against the nonspecific adsorption of proteins was discussed.     

Amino acids and peptides. XXXV. Facile preparation of p-nitroanilide analogs by the solid-phase method

p-Nitroanilides of amino acids and peptides are widely used as the chromogenic substrates for the determination of the activity of proteolytic enzymes. However, the preparation of a p-nitroanilide is not easy, in part due to the low nucleophilicity of the amino group of p-nitroaniline. A facile preparation of p-nitroanilide analog by the solid-phase method was investigated. 5-Amino-2-nitrobenzoic acid (Anb5,2) was used instead of p-nitroaniline (pNA) for preparation of p-nitroanilide analogs. Anb5,2 was introduced on a p-methylbenzhydrylamine resin without protection of the amino group of Anb5,2 by the 2-(H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) method in the presence of p-dimethylaminopyridine. The coupling reaction of a Nalpha-,NG-protected arginine with a Anb5,2-resin was difficult to achieve by common coupling methods (such as the carbodiimide and diphenylphosphoryl azide methods), but the phosphoryl chloride method was relatively successful. Synthetic benzoyl-Arg-Anb5,2-NH2 and benzoyl-Arg-pNA were hydrolyzed by trypsin and the both reaction mixtures exhibited same spectroscopic characteristics. H-D-Val-Leu-Arg-Anb5,2-NH2, an analog of human urine kallikrein substrate, was readily prepared by the solid-phase method. H-Arg-Anb5,2-OH and H-D-Val-Leu-Arg-Anb5,2-OH were also synthesized on a Wang resin by the solid-phase method. The aqueous solubility of these free-carboxyl materials was better than those of the corresponding amide analogs. 4-Amino-3-nitrobenzoic acid (Anb4,3) was also introduced on the p-methybenzhydrylamine resin, but the resulting H-Anb4,3-resin did not react with Nalpha,NG-protected arginine by any of the coupling methods.     

The sennoside constituents of rhei rhizoma and sennae folium as inhibitors of serum monoamine oxidase

Four (in total) compounds with inhibitory effects on the activity of bovine serum monoamine oxidase were isolated from the methanol-water extracts of Rhei Rhizoma (Daiou) and Sennae Folium (Senna), and identified as sennosides A, B, E and F. Among them, sennosides A and B were obtained from both Rhei Rhizoma and Sennae Folium, while sennosides E and F were detected only in the former. The 50% inhibitory concentrations of the four sennosides were 17, 9, 24 and 13 microM, respectively, and the type of inhibition by seenosides A and B with respect to allylamine as the substrate was non-competitive.     

Resin glycosides. XV. Simonins I-V, ether-soluble resin glycosides (jalapins) from the roots of Ipomoea batatas (cv. Simon).

Five new ether-soluble resin glycosides (jalapins), simonins I-V, have been isolated from the roots of Ipomoea batatas and characterized on the bases of chemical and spectral data. Simonin I is the first example of resin glycoside with aromatic acid (trans-cinnamic acid) as a component organic acid.     

Industrial production of L-2-amino-4-phenylbutyric acid from 2-oxo-4-phenylbutyric acid by paracoccus denitrificans containing aminotransferase activity

An industrial production method of L-2-amino-4-phenylbutyric acid from 2-oxo-4-phenylbutyric acid by microbial cells containing aminotransferase activity was investigated. By usingParacoccus denitrificans pFPr-1, 0.19M L-2-amino-4-phenylbutyric acid was produced with a 95% conversion yield. Accumulated L-2-amino-4-phenylbutyric acid was readily isolated in pure form. Overall yield from 2-oxo-4-phenylbutyric acid was 83.7%.     

The absolute configuration of the side chain diol moiety of the poison-frog alkaloid pumiliotoxin B

The absolute configuration of the diol moiety in the side chain of pumiliotoxin B has been established by comparison of the ozonolysis product from pumiliotoxin B diacetate with the synthetic 3,4-diacetoxy-2-pentanone derived from L-(+)-tartaric acid. This indicates the absolute configuration (R, R) of C-15, C-16 diol of pumiliotoxin B.     

Utility of the iridium complex of the pybox ligand in regio- and enantioselective allylic substitution

The viability of the iridium complex of pybox as chiral catalyst in allylic substitutions and the enantioselective synthesis of branched products was studied. Among several chiral ligands evaluated, the iridium complex of pybox having a phenyl group catalyzed the reaction with high activity to form the branched amines with good enantioselectivities when hydroxylamine, amine, and aniline were employed as a nucleophile. The allylic substitution with oximes proceeded smoothly to give the branched oxime ethers with good enantioselectivities. [reaction: see text]     

Reduction of Iron(III) Ion by Activated Carbon Fiber

The mechanisms of adsorption of iron(II) ion, iron(III) ion, and reduced iron(III) ion onto an activated carbon fiber and the ability of carbon fibers to reduce iron(III) ion were investigated on the basis of the amounts of iron ion adsorbed. The amount of iron(II) ion adsorbed onto the activated carbon fiber increased with increasing adsorption temperature. Iron(II) ion was more easily removed by the activated carbon fiber than iron(III) ion. Iron(III) ion was adsorbed onto the activated carbon fiber after being reduced to iron(II) ion. The reduction ability of A-20 was stronger than that of A-10 because the hydrophilic groups of A-20 were larger than those of A-10. It is concluded that the activated carbon fiber has a reduction effect on iron(III) ion and that the reduction effect of the activated carbon fiber depended on the number of hydrophilic groups on the activated carbon fiber. Copyright 2000 Academic Press.