Direct and stereoselective synthesis of β-d-mannosides using 4,6-O-benzylidene-protected mannosyl diethyl phosphite as a donor

A direct and practical method for the construction of β-mannosidic linkages is described. While β-selectivities in the TMSOTf-promoted glycosidation of 2,3,4,6-tetra-O-benzyl-d-mannosyl diethyl phosphite are found to be highly dependent on the reactivity of acceptor alcohols, 2,3-di-O-benzyl-4,6-O-benzylidene-d-mannosyl diethyl phosphite reacts with a wide range of acceptor alcohols in the presence of TMSOTf in CH₂Cl₂ at −45 °C to give β-mannosides in high yields with good to high β-selectivities.     

New steroidal alkaloids from Fritillaria imperialis and their cholinesterase inhibiting activities

Two new cevanine steroidal alkaloids, impericine (1) and forticine (2) along with known bases delavine (3), persicanidine A (4), and imperialine (5) were isolated from the bulbs of Fritillaria imperialis. The structures of impericine (1) [(20R,22S,25S)-5alpha-cevanin-23-ene-3beta,6beta,16beta-triol] and forticine (2) [(20S,22S,25S)-5alpha-cevanine-3beta,6beta-diol] were determined with the help of spectroscopic studies. These steroidal bases showed anti-acetylcholinesterase and anti-butyrylcholinesterase inhibitory activity.     

Electrical conduction through linear porphyrin arrays

Electrical conduction measurements were made on two extreme types of directly linked porphyrin arrays by using nanoelectrodes. One type is the directly linked Zn(II)porphyrin arrays, consisting of 48 Zn(II)porphyrin moieties (Z48), and the other type is the completely flat, tape-shaped Zn(II)porphyrin arrays, consisting of eight Zn(II)porphyrin units (T8). The I-V curve for Z48 exhibits the diode-like behavior and the hysteresis depending on the voltage sweep direction presumably due to the conformational heterogeneity arising from the dihedral angle distribution in Z48. On the other hand, the I-V curve for T8 is nearly symmetric without any hysteresis, leading to the higher conductivity and the smaller band gap. These results illustrate that the stronger pi-electron conjugation in T8, as compared with that of Z48, results in better electrical conduction.     

Preparation of red blood cell column for capillary electrochromatography.

A column packed with red blood cells (RBCs) was prepared for electrochromatography as a separation and reaction column. RBCs were kept inside a piece of fused silica capillary tubing with 2% agarose gel. In the column, RBCs were uniformly distributed in the agarose gel matrix and their electrophoretic movements due to an applied voltage were suppressed well. The durability of the biological function of the column under applied voltage was about 1 h, although it could remain for 2-3 days without applied voltage. The column could not be used when hemolysis of the RBCs was observed in the column. When the developed "RBC-gel column" was used, both pyridoxamine and serotonin were converted to other compounds through their direct contact with RBCs.     

Synthesis of 1-triazolyl-4-trimethylsilyl-2-butanol and 1-triazolyl-5-trimethylsilyl-2-pentanol derivatives and an investigation of their fungicidal activities

A new series of azole derivatives of 1-triazolyl-4-trimethylsilyl-2-butanol and 1-triazolyl-5-trimethylsilyl-2-pentanol were synthesized and evaluated for fungicidal activities against rice blast, sheath blight, and powdery mildew on barley. The derivatives of 2,4-difluorobenzene exhibited high antifungal activities when applied by spray, but exhibited no fungicidal activity by submerged application.     

Acid-catalyzed degradation mechanism of poly(phthalaldehyde): Unzipping reaction of chemical amplification resist

The acid-catalyzed degradation mechanism of chemical amplification resists based on end-capped poly(phthalaldehyde) has been elucidated by semi-empirical molecular orbital calculations. It is concluded that: (i) two different starting points exist in the degradation of end-capped poly(phthalaldehyde), the central part of the polymer as well as the polymer end; (ii) in both cases, after the first protonation, cationic hydroxyl compounds generated decompose to the identical cation intermediate, which can unzip itself to phthalaldehyde monomers successively (unzipping reaction); (iii) the hemiacetal type intermediates hardly degrade to the same intermediate without acid catalyst; (iv) the overall activation energy for the degradation reaction is less than 14 kcal/mol in all the cases. Thus, the poly(phthalaldehyde) resist can easily self-develop below 100°C, as reported in the literature. © 1997 John Wiley & Sons, Inc.     

Amino acids and peptides. LV. Application of 2-adamantyl derivatives as protecting groups to the synthesis of peptide fragments related to Sulfolobus solifataricus ribonuclease. II.

Segment condensations were performed to construct peptide fragments related to Sulfolobus solifataricus Ribonuclease. At each condensation step, the new protecting groups were stable. The protected peptide fragments were treated with a low-high HF procedure to give the desired peptide fragments. These peptide fragments were also prepared by the solid-phase method, and the obtained peptides were compared with those obtained by the solution method. The peptide fragments obtained by the solution method were identical with those obtained by the solid-phase method on analytical HPLC, indicating that the new protecting groups could be easily removed by HF, and no racemization occurred during the synthesis of the protected peptides.     

Synthesis of pyrazinone ring-containing opioid mimetics and examination of their opioid receptor-binding activity.

Cyclization of dipeptidyl chloromethyl ketones gave 6-(4-aminobutyl)-3-carboxyethyl-5-methyl-2(1H)-pyrazinone, 3-(4-aminobutyl)-6-carboxyethyl-5-methyl-2(1H)-pyrazinone, and 3,6-bis(4-aminobutyl)-5-methyl-2(1H)-pyrazinone, which were inserted into the enkephalin sequence to give opioid mimetics. Thus, it was confirmed that a pyrazinone ring can be easily inserted into a peptide sequence in order to evaluate structural components required for biologically active peptides.     

An ab initio theoretical research on perfluorochemicals as oxygen carriers

In order to elucidate the nature of the interaction force effected in perfluorochemical artificial blood, the basis set dependence of the stabilization energy between a model perfluorochemical and oxygen was investigated in detail. The basis set superposition error was removed in each case. The interaction was estimated to arise from dispersion forces.