Synthesis of novel 1,4-, 3,4-, and 4,5-dihydropyrimidines: First successful POCl3 chlorination and regioselective alkoxycarbonylation

Chlorination of 5,6-dihydropyrimidine-4-(3H)-one derivatives (1) with POCl₃ gave 1,4(3,4)-dihydropyrimidines (3), whose alkoxycarbonylation (ClCOOREt₃N or NaH) afforded regioselectively novel compounds (4). A new Pummerer rearrangement of compound (1, X= ---S(O)CH₃) with ₃, gave compound (5h).     

A direct identification method for current dipoles from electromagnetic fields

We discuss the identification problem for current dipoles in a spherically symmetric conductor. This mathematical model is used for a biomedical inverse problem such as the source current identification for the human brain activity. We have already proposed a direct identification method for this inverse source problem using observations of the magnetic fields outside of the conductor. One of the difficulties of current dipole identification using the magnetic fields is caused by the fact that magnetic field does not include any information about the radial component of dipole moments. In this paper, we consider an improvement of the direct method to identify both radial and tangential components of current dipole moments by combining electric and magnetic observation data. Furthermore, our approach is effective in the case where the number of dipoles is unknown.     

Polarographic studies on the electrode kinetics of the nickel(II) complexes with glycine and some of its derivatives: I. glycine complexes

D.C. polarograms of the Ni(II)-glycine complexes were measured with varying pH values at constant total glycine concentration (0.05 M) and conversely with varying total glycine concentration at constant pH values (3.5, 4.5, 7.5 and 9.5). The current—voltage curves obtained were analysed to determine the limiting currents, the transfer coefficients, and the half-wave potentials, by using the non-linear least squares method. From the dependence of the half-wave potentials on the free glycine concentration, the mechanism of the electrode processes was elucidated. It was shown that the first wave corresponded to the reduction of the Ni²⁺ aquo-complex, the second to the NiG⁺ complex, the third to the NiG₂ complex and the fourth to the NiG^?₃ complex. The kinetic parameters for the four charge transfer processes were determined.The second and third waves were kinetic in character and the rate constants of the dissociation and association reactions between NiG⁺ and NiG₂ and between NiG₂ and NiG^?₃ were determined by analysing the dependence of the kinetic limiting currents on the free glycine concentration.     

Systematic Measurement of pd Breakup Cross Section Around Space Star

Space Star (SS) anomaly in nd breakup cross section was first reported in 1989 at E _n = 13 MeV (Strate et al. in Nucl Phys A 501:51, 1989), but its origin has not been found yet. In order to obtain suggestions for its origin, we made systematic measurements of pd breakup cross section around SS. In SS configuration, three outgoing nucleons form an equilateral triangle and the triangle is perpendicular to the beam axis. Necessity of the equilateral and perpendicular conditions of SS anomaly was investigated by systematic experiments. Also energy dependence of SS anomaly is being studied at energies from E _p = 7.5 to 13 MeV.     

Concise asymmetric total synthesis of scyphostatin, a potent inhibitor of neutral sphingomyelinase

The concise asymmetric total synthesis of scyphostatin has been achieved by condensation of the optically active cyclohexane unit, prepared from the commercially available 1,4-cyclohexadiene by our own method, and the side chain, prepared by the method developed by Hoye and Tennakoon (T. R. Hoye, M. A. Tennakoon, Org. Lett. 2000, 2, 1481-1483). The modification of the epoxy cyclohexenone unit was achieved in a late stage of the total synthesis, and deprotection of the primary alcohol was conducted in the final step. During the synthesis several key reactions were attained: 1) intramolecular bromoetherification of the cyclohexadiene acetal; 2) stereoselective introduction of the tertiary alcohol, 3) deprotection of the acetal function to the aldehyde by combination with silyl triflate/2,4,6-collidine and the one-pot synthesis of the disilyl aldehyde compounds, with different types of silyl groups, from the dihydroxy acetal compounds; and 4) facile deprotection of the 2,4-dimethoxyphenylmethyl ((2,4)DMPM) protecting group of the primary alcohol.     

Reaction of Acetals with Various Carbon Nucleophiles under Non‐Acidic Conditions: C?C Bond Formation via a Pyridinium‐Type Salt

Mild substitution reactions of acetals with carbon nucleophiles via the pyridinium‐type salts generated by the treatment of acetals with TESOTf‐2,4,6‐collidine or 2,2′‐bipyridyl have been developed. Various carbon nucleophiles, such as organocuprates, silyl enol ethers, enamines, etc., reacted with the pyridinium‐type salts to give the corresponding substituted products in good yields. The reactions proceeded under very mild conditions (non‐acidic conditions) and thus acid‐sensitive functional groups can be tolerated during the reaction. In addition, only an acetal can form the pyridinium‐type salt and react with nucleophiles in the presence of a ketal. This unusual selectivity is in contrast to general methods conducted under acidic conditions.     

Levitation of metallic melt by using the simultaneous imposition of the alternating and the static magnetic fields

This study developed a new levitation method, which used the simultaneous imposition of static and alternating magnetic fields. Dynamic behavior was measured for pure Cu and pure Ni melts levitated by the proposed method. The oscillation due to surface tension and convection in levitated Cu melts were hardly observed at static magnetic fields exceeding 1 T. Only the rotation of this axis parallel to the static magnetic field was observed under high static magnetic fields. The proposed method demonstrated that metallic melt could be statically levitated like a solid sphere. It was also found that stable levitation of paramagnetic Ni melt was rather difficult at static magnetic fields exceeding 5 T, because of the magnetization force.     

Organic chemistry using weakly electrophilic salts: efficient formation of O,O-mixed, O,S- and N,O-acetals

A mild and efficient method for the preparation of O,O-mixed, O,S- and N,O-acetals from symmetrical O,O-acetals has been developed. Thus, the treatment of symmetrical O,O-acetals with TESOTf and 2,4,6-collidine formed weakly electrophilic collidinium salts. The addition of nucleophiles, such as an alcohol, lithium thioxide, and sodium azide, to the salts afforded the corresponding O,O-mixed, O,S- and N,O-acetals in good yields. The reaction proceeded under weakly basic conditions. No overreaction then occurred and many acid-labile functional groups could remain intact.     

On a numerical solution of the Cauchy problem for the Laplace equation by the fundamental solutions method

We discuss a numerical method to solve a Cauchy problem for the Laplace equation in the two-dimensional annular domain. We consider the case that the Cauchy data is given on an arc. We develop an approximation method based of the fundamental solutions method using the least squares method with Tikhonov regularization. The effectiveness of our method is examined by a numerical experiment. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)