Oxidative kinetic resolution of racemic alcohols catalyzed by chiral ferrocenyloxazolinylphosphine-ruthenium complexes

Oxidative kinetic resolution of racemic secondary alcohols by using acetone as a hydrogen acceptor in the presence of a catalytic amount of [RuCl(2)(PPh(3))(ferrocenyloxazolinylphosphine)] (2) proceeds effectively to recover the corresponding alcohols in high yields with an excellent enantioselectivity. When 1-indanol is employed as a racemic alcohol, the oxidation proceeds quite smoothly even in the presence of 0.0025 mol % of the catalyst 2 to give an optically active 1-indanol in good yield with high enantioselectivity (up to 94% ee), where turnover frequency (TOF) exceeds 80,000 h(-1). From a practical viewpoint, the kinetic resolution is investigated in a large scale, optically pure (S)-1-indanol (75 g, 56% yield, >99% ee) being obtained from racemic 1-indanol (134 g) by employing this kinetic resolution method twice.     

A potentiometric enzyme electrode for monitoring in organic solvents

A potentiometric enzyme electrode is described for monitoring reactions in organic solvents. By use of an enzyme deposited on magnetic particles which are attracted to the tip of the electrode by means of a magnetic field, it is possible to produce an electrode in which the enzyme can easily be exchanged. As an example, studies of the chymotrypsin-catalyzed ester synthesis in diisopropyl ether and in toluene at varying water contents are reported. The results are consistent with those obtained from batch experiments. Operational behaviour and signal stability of the system makes this kind of potentiometric enzyme electrode attractive for monitoring bioorganic processes.     

ENERGY TRANSFER FROM SODIUM N-ALKYL CARBAZOLE SULFONATE TO ZINC TETRAPHENYLPORPHYRIN IN MICELLAR SOLUTIONS

Abstract— In order to study energy transfer to zinc tetraphenylporphyrin (ZnTPP) in micellar solution, a series of surface active agents of sodium N-alkyl carbazole sulfonate, were synthesized. The energy transfer efficiency from the carbazole group near the surface to ZnTPP located in the core of sodium lauryl sulfate (NaLS) micelles was found to be 30%, as observed through the fluorescence of ZnTPP. The critical micelle concentrations (CMC) of the sodium N-alkyl carbazole sulfonate surfactants, determined by scattering, were 2 times 10_-4 M, 3 times 10_-5M and 3 times 10_-6 M, respectively, for alkyl: octyl, dodecyl and hexadecyl. The sensitivity of the CMC of NaLS to the presence of foreign surfactants and solubilizates was also investigated.     

Total synthesis of (+/-)-garsubellin A

The first total synthesis of garsubellin A, a neurotrophic compound with potent choline acetyltransferase-inducing activity, is described. Keys for success were (1) stereoselective intermolecular aldol reaction at the C-4 position with acetaldehyde, (2) stereoelective Claisen rearrangement to introduce an allyl group to the most sterically crowded position at C-6, (3) ring-closing metathesis to construct the B-ring, and (4) Wacker-type oxidative C-ring formation. This synthetic route can be extended to an asymmetric synthesis of garsubellin A using the Koga catalytic enantioselective alkylation, which produced enantioenriched alpha-prenyl cyclohexenone with excellent enantioselectivity (95% ee).     

Trypsin-catalyzed synthesis of dipeptide containing alpha-aminoisobutyric acid using p- and m-(amidinomethyl)phenyl esters as acyl donor

Two series of inverse substrates, p- and m-(amidinomethyl)phenyl esters derived from N-(tert-butyloxycarbonyl)amino acid, were prepared as acyl donor components for enzymatic peptide synthesis. They were found to be readily coupled with an acyl acceptor such as L-alanine p-nitroanilide to produce dipeptide. An alpha-aminoisobutyric acid containing dipeptide was especially obtained in satisfactory yield. Streptomyces griseus trypsin was a more efficient catalyst than the bovine trypsin. The optimum condition for the coupling reaction was studied by changing the organic solvent, pH, and acyl acceptor concentration. It was found that the enzymatic hydrolysis of the resulting product was negligible.     

Methanol oxidation on a Pt(111)-OH/O surface

The methanol oxidation on a hydroxylated Pt (Pt(111)-OH) surface has been investigated by means of infrared reflection absorption spectroscopy (IRAS) in ultra-high vacuum (UHV) and in acidic solution. The Pt(111)-OH surface in UHV was prepared by introducing water molecules on a Pt(111)-(2 x 2)-O surface and annealed at temperature higher than 160 K. Methanol was then, introduced to the Pt(111)-OH surface to show the dependence of the reaction intermediate on the annealing temperature. At an annealing temperature below 160 K, IR bands assignable to methanol overlayer were observed and no detectable intermediates, such as CO, formaldehyde and formate, were formed, suggesting that methanol molecules remain stable on Pt(111) surface without dissociation at this temperature region. At an annealing temperature above 160 K, on the other hand, CO and formate were observed. In addition, the oxidation of CO on Pt(111)-OH showed no sign of formate formation, indicating that formate is not derived from CO, but from a direct oxidation of methanol. Methanol oxidation was carried out in 0.1 mol dm(-3) HClO(4) solution on Pt(111) with a flow cell configuration and showed the formation of formate. These results indicate that the formate is the dominant non-CO intermediate both in UHV and in acidic solution, and the preadsorbed oxygen-containing species, in particular OH adsorbates, on Pt(111) surface plays a very important role in the formate formation process in methanol oxidation reaction.     

Microstructure evolution in Stöber-type silica nanoparticles and their in vitro apatite deposition

Prepared via Stöber-type sol–gel routes were three types of silica particles of <1 μm in size: pure silica, Ca-involving silica, and chitosan/alginate-coated silica with a polymershell-silica core structure. Calcium ions were impregnated in the organic layers of the polymer-coated silica particle. The sol–gel procedure was applied to tetraethoxysilane dissolved in an ethanol/water mixture, while Ca–silica was derived from CaCl₂-containing ethanol/water solutions. Scanning and transmission electron micrograph analyses indicated that those silica particles consisted of ~10 nm primary particles, the Ca–silica particles (~500 nm) were larger than the Ca-free ones (~200 nm) and that their size increased with the Ca concentration in the precursor solutions. From ¹H- and ²⁹Si- magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra and ²⁹Si cross-polarization NMR spectra, the mechanism of primary particle agglomeration and degradation of the secondary particles in saline were discussed in terms of the content of H₂O molecules and >Si–OH as well as hydrogen bonding interactions among them. In addition, the Ca–silica and core-shell silica deposited apatite in Kokubo’s simulated body fluid. Thus, the present Ca–silica and polymer-coated silica particles were suggested to be applicable to injectable bone fillers for bone generation.     

Covalent immobilization of antibody fragments on well-defined polymer brushes via site-directed method

Well-defined polymer brushes and block copolymer brushes consisting of 2-methacryloyloxyethyl phosphorylcholine (MPC) and glycidyl methacrylate (GMA) were prepared by surface-initiated atom transfer radical polymerization (ATRP). The polymer brushes were used for the immobilization of antibody fragments in a defined orientation. Pyridyl disulfide moieties were introduced to the polymer brushes via a reaction of epoxy groups in GMA units. Fab’ fragments were then immobilized onto these surfaces via a thiol-disulfide interchange reaction and the reactivity of antibodies with antigens was investigated. Antigen/antibody binding on the polymer brushes was more preferable than that on epoxysilane films as a control surface. Furthermore, the activity of the antibodies immobilized on the block copolymer brushes having biocompatible PMPC was greater than that on other surfaces that did not have PMPC in their structures.     

Dynamical observation of structural transition of polymers using an X‐ray diffraction system with imaging plates. II. Crystalline transition of poly(butylene terephthalate)

Poly(butylene terephthalate) has two crystalline forms of α and β. The α form is more stable and is transformed into the β form by stretching. The α↔β transition stress was measured at various temperatures with the use of an X‐ray diffraction system with imaging plates, and the relationship between the transition stress and temperature was obtained. Further, using the X‐ray diffraction system, the drawing behavior of the nearly amorphous, undrawn polymer film was observed by taking up dynamically a series of X‐ray diffraction patterns while a film was being drawn. The α form never occurred during drawing at any temperature because the stress to draw the film exceeded the α→β transition stress. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 838–845, 2000     

Synthesis and Characterization of Gelatin-Siloxane Hybrids Derived through Sol-Gel Procedure

A new type of inorganic-organic hybrid materials incorporating gelatin and 3-(glycidoxypropyl) trimethoxysilane (GPSM) was prepared through sol-gel processing. A solid-state ²⁹Si NMR analysis indicated that all the methoxy silane groups of GPSM were polymerized to yield —Si—O—Si— bridging bonds. An amino acid analysis confirmed grafting reactions of GPSM against gelatin chains. The increasing GPSM/gelatin ratio stimulated gel formation, phase separation, and the density of GPSM-crosslinking of the gelatin chains as well as it changed the micro- and macro- structures and the viscoelastic properties of the final products.