Synthetic study of 1-substituted carbapenem antibiotics

Total synthesis of 1-substituted carbapenems is described. The key step is the reaction of acetoxyazetidinone ($\text{7}$) with ketene silyl acetal ($\text{8}$).     

Synthesis of quinoxaline 1,4-dioxides from 4,5(6,7)-dimethylbenzofuroxan

In this study, novel substituted quinoxaline 1,4-dioxides were synthesized from novel substituted benzofuroxan. 4,5(6,7)-Dimethylbenzofuroxan 3 was prepared by the thermal decomposition of 2,3-dimethyl-6-nitrophenylazide 2 . Novel quinoxaline 1,4-dioxides derivatives were obtained using compound 3 and the enolic form of 1,3-diketones 4 catalyzed by silica gel or molecular sieves. These reactions gave isomeric quinoxaline 1,4-dioxides 5 and 6 . These reactions of compound 3 may involve tautomers 4,5-dimethylbenzofuroxan 3a , 6,7-dimethylbenzofuroxan 3b on the surface of a solid catalyst.     

Pulse injection analysis of the binding of serum proteins to porous polymer gels modified with formyl groups

Highly porous spherical polymer gels were modified with formyl groups by a modified Friedel-Crafts reaction and the interaction of serum proteins with the modified gels were examined by pulse injection analysis. The introduction of formyl groups into the polymer greatly increases its protein-binding capacity, and the protein bound to the gel is not eluted by washing with acid, alkali or urea solution. The effects of temperature and the percentage of formyl group substitution on the binding capacity indicate that the binding process can be interpreted as initial approach of the protein to the polymer surface, caused by the hydrophobic interaction, followed by formation of a stable Schiff base between the polymer gel and the protein. Theoretical treatment of the elution behaviour of the protein from the polymer-packed column is also examined, with the assumption that there are three kinds of binding site in the polymer gel: surface, macropore and micropore regions. These polymers are shown to be useful for the removal of proteins from biological samples in clinical assays using immobilized enzymes.     

Electron transfer in metal-molecule-metal junction composed of self-assembled monolayers of helical peptides carrying redox-active ferrocene units

Electronic properties of three kinds of helical peptides with or without redox-active ferrocene units were investigated by using scanning tunneling microscopy under ultrahigh vacuum. The currents through the helical peptides carrying ferrocene units at the molecular terminals became significantly larger than that through a reference peptide without any ferrocene units. On the other hand, ferrocene units in the middle of the peptide chain did not affect the current-voltage characteristics. These results indicate that the ferrocene units near the metal electrode should play an important role for efficient electron transfer between the metal and the peptide molecules, which process is one of the rate-determining steps for characterizing molecular conductance in metal-molecule-metal junction.     

Nonlinear magnetooptical effects caused by piezoelectric ferromagnetism in F3m-type Prussian blue analogues

The second harmonic generation (SHG) and magnetization-induced SHG (MSHG) of AMA[MB(CN)6]-type (F3m) Prussian blue analogues (i.e., CsCo[Cr(CN)6].0.5H2O and RbMn[Fe(CN)6]) were observed. A large interaction between the nonlinear optical response and magnetic spins was observed in CsCo[Cr(CN)6].0.5H2O. These observations of SHG and MSHG imply that AMA[MB(CN)6]-type Prussian blue analogues are piezoelectric above the Curie temperature (TC) and piezoelectric ferromagnet below TC.     

Silica monolithic membrane as separation medium. Summable property of different membranes for high-performance liquid chromatographic separation

We studied an applicability of a silica monolithic membrane as separation medium for high-performance liquid chromatography (HPLC). We prepared porous monolithic silica membranes having a three-dimensional network structure to cut and shape into a membrane separation medium. We evaluated chromatographic properties of a variety of solutes using a column containing the membranes with HPLC to elucidate summable property of the membrane separation media. In addition, we made brief study on separation of HbA1c in whole blood with the stacked" membranes having different surface characteristics in one column, which is a membrane column. We confirmed that the membrane column was able to separate HbA1c from other matrix in whole blood to some extent, and it also had an excellent ability for hydrophobic and ion exchange adsorption.     

Anodic modification of proline derivatives using a lithium perchlorate/nitromethane electrolyte solution

[reaction: see text] N-Acyliminium cation of prolines was efficiently generated to accumulate in an undivided cell at 0 degrees C by an anodic oxidation of N-acylprolines or alpha'-phenylsulfanylated N-acylproline derivatives in a lithium perchlorate/nitromethane solution. The iminium cation intermediates gave modified prolines by a reaction with nucleophiles under mild conditions.     

Combination of an aromatic core and aromatic side chains which constitutes discotic liquid crystal and organogel supramolecular assemblies

This paper reports unique and unusual formations of columnar liquid crystals and organogels by self-assembling discotic molecules, which are composed of an aromatic hexaazatriphenylene (HAT) core and six flexible aromatic side chains. In HAT derivatives 3a, with 4'-(N,N-diphenylamino)biphenyl-4-yl chains, 3b, with 4'-[N-(2-naphthyl)-N-phenylamino]biphenyl-4-yl chains, and 3c, with 4'-phenoxybiphenyl-4-yl chains, the two-dimensional hexagonal packings can be created by their self-assembling in the liquid crystalline phase, which were characterized by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction analysis. In certain solvents, HAT molecules 3a-c can form the viscoelastic fluid organogels, in which one-dimensional aggregates composed of the HAT molecules are self-assembled and entangled into three-dimensional network structures. The organogel structures were analyzed by scanning electron microscopy observation, (1)H NMR, UV-vis, and circular dichroism spectroscopy. In contrast to 3a-c, none of the liquid crystalline and organogel phases could be formed from 3d and 3e with short aromatic side chains including a phenylene spacer, and 3f (except a few specific solutions) and 3g without terminal diarylamino and phenoxy groups. In 3a-c, the aromatic side chains with terminal flexible groups make up soft regions that cooperatively stabilize the liquid crystalline and organogel supramolecular structures together with the hard regions of the hexaazatriphenylene core.     

Aerobic catechol oxidation catalyzed by a bis(mu-oxo)dimanganese(III,III) complex via a manganese(II)-semiquinonate complex

A 3,5-di-tert-butyl-1,2-semiquinonato (DTBSQ) adduct of Mn(II) was prepared by a reaction between Mn(II)(TPA)Cl(2) (TPA = tris(pyridin-2-ylmethyl)amine) and DTBSQ anion and was isolated as a tetraphenylborate salt. The X-ray crystal structure revealed that the complex is formulated as a manganese(II)-semiquinonate complex [Mn(II)(TPA)(DTBSQ)](+) (1). The electronic spectra in solution also indicated the semiquinonate coordination to Mn. The exposure of 1 in acetonitrile to dioxygen afforded 3,5-di-tert-butyl-1,2-benzoquione and a bis(mu-oxo)dimanganese(III,III) complex [Mn(III)(2)(mu-oxo)(2)(TPA)(2)](2+) (2). The reaction of 2 with 3,5-di-tert-butylcatechol (DTBCH(2)) quantitatively afforded two equivalents of 1 under anaerobic conditions. The highly efficient catalytic oxidation of DTBCH(2) with dioxygen was achieved by combining the above two reactions, that is, by constructing a catalytic cycle involving both manganese complexes 1 and 2. It was revealed that dioxygen is reduced to water but not to hydrogen peroxide in the catalytic cycle.     

Dielectrophoretic micropatterning with microparticle monolayers covalently linked to glass surfaces

Two-dimensional micropatterns of microparticles were fabricated on glass substrates with negative dielectrophoretic force, and the patterned microparticles were covalently bound on the substrate via cross-linking agents. The line and grid patterns of microparticles were prepared using the repulsive force of negative dielectrophoresis (n-DEP). The template interdigitated microband array (IDA) electrodes (width and gap 50 mum) were incorporated into the dielectrophoretic patterning cell with a fluidic channel. The microstructures on the glass substrates with amino or sulfhydryl groups were immobilized with the cross-linking agents disuccinimidyl suberate (DSS) and m-maleimidobenzoyl-N-hydroxy-succinimide ester (MBS). Diaphorase (Dp), a flavoenzyme, was selectively attached on the patterned microparticles using the maleimide groups of MBS. The enzyme activity on the patterned particles was electrochemically characterized with a scanning electrochemical microscope (SECM) in the presence of NADH and ferrocenylmethanol as a redox mediator. The SECM images proved that Dp was selectively immobilized onto the surface of microparticles to maintain its catalytic activity.