A stereoselective cyclisation cascade mediated by SmI2–H2O: synthetic studies towards stolonidiol

A cascade reaction involving sequential conjugate reduction, stereoselective aldol cyclisation and chemoselective lactone reduction mediated by SmI₂–H₂O provides access to a cyclopentanol bearing two vicinal quaternary stereocentres with good stereocontrol. The functionalised cyclopentanol product has been converted to a key intermediate in ongoing asymmetric studies towards stolonidiol.     

Determination of the Distribution of Cupric Chloro-Complexes in Hydrochloric Acid Solutions at 298 K

The distribution of metal-chloro complexes in hydrochloric acid solutions is a fundamental aspect of anion exchange reactions that allows ultrahigh purification during hydrometallurgical processes. However, these exchange reactions are not yet understood in detail. To clarify and improve anion exchange separation so as to obtain a more sophisticated purification process, it is necessary to accurately determine the distribution of metal-chloro complexes. In the present work, cupric-chloro complexes were investigated because copper is one of the most important base metals in modern society. The absorption spectra of solutions of these complexes were acquired at 298 K and analyzed by multivariate curve resolution–alternating least squares method (MCR–ALS), a factor analysis technique widely used in chemometrics. The resulting cupric-chloro complex distributions were fitted with a thermodynamic model using appropriate activity coefficients extended to the concentrated solutions. These calculations employed a modified Debye–Hückel model because the distributions acquired through the model-free MCR–ALS analysis were less meaningful, both physically and chemically. It was concluded that five [Cu^IICl _n ]^2?n species, where n = 0–4, are present in the hydrochloric acid solutions. In addition, cumulative formation constants and pure molar attenuation coefficients were obtained.     

Internal delivery of soft chlorine and bromine atoms: stereoselective synthesis of (E)-beta-halogenovinyl(aryl)-lambda3-iodanes through domino lambda3-iodanation-1,4-halogen shift-fluorination of alkynes

4-(Difluoroiodo)toluene-induced domino lambda(3)-iodanation-1,4-halogen shift-ring enlargement-fluorination reaction of 5-halopentynes with a four-, five-, or six-membered carbocycle afforded the ring-expanded (E)-delta-fluoro-beta-halovinyl-lambda3-iodanes stereoselectively in high yields, probably via the intermediacy of five-membered halonium ions. Use of internal alkynes makes it possible to synthesize tetrasubstituted beta-halovinyl-lambda(3)-iodanes with defined stereochemistry.     

Stability of solitary waves for the Ostrovsky equation

Considered herein is the Ostrovsky equation which is widely used to describe the effect of rotation on the surface and internal solitary waves in shallow water or the capillary waves in a plasma. It is shown that the solitary-wave solutions are orbitally stable for certain wave speeds.

     

Abnormal Li diffusion in β-LiGa by the formation of defect complex

The diffusion coefficients of Li in the NaTl-type Li intermetallic compound of β-LiGa have been measured by using a short-lived radioactive diffusion tracer. As the tracer, the α-emitting radioisotope of ⁸Li delivered as the energetic and pulsed beam from Tokai Radioactive Ion Accelerator Complex (TRIAC) was implanted into the β-LiGa compounds with the composition in the range of about 43 to 54 at.% Li. By analyzing the time-dependent yields of the α-particles measured according to the repetition cycle of the beam, the tracer diffusion coefficients were extracted over the wide range of Li composition. Abnormal composition-dependence of Li diffusion coefficients in β-LiGa was observed; the stoichiometric β-LiGa showed the highest diffusivity of Li. By referring to the composition-dependent diffusivity of Li in the iso-structural β-LiAl and β-LiIn, we could identify the abnormal diffusion of Li in very Li-poor composition of β-LiGa. The anomaly has been discussed qualitatively in terms of the formation of defect complex and the interaction between the constitutional defects.     

Strong instability of solitary waves for nonlinear Klein–Gordon equations and generalized Boussinesq equations

We study here instability problems of standing waves for the nonlinear Klein–Gordon equations and solitary waves for the generalized Boussinesq equations. It is shown that those special wave solutions may be strongly unstable by blowup in finite time, depending on the range of the wave's frequency or the wave's speed of propagation and on the nonlinearity.     

Critical Blowup for Systems of Semilinear Wave Equations in Low Space Dimensions

We consider the Cauchy problem for systems of semilinear wave equations in two and three space dimensions with small initial data. Del Santo et al. [“Geometric Optics and Related Topics” (F. Colombini and N. Lerner, Eds.), Progress in Nonlinear Differential Equations and Their Applications, Vol. 32, pp. 117–140, Birkhauser, Boston, 1997] have studied the existence and nonexistence of global classical solutions of the Cauchy problem except for the critical case. In this paper we study the critical case, and we show the nonexistence of global classical solutions and also give the upper bounds of the life span.     

Orbital stability of solitary waves for a higher-order nonlinear Schrödinger equation

We show by the variational method that there exist orbitally stable solitary waves of a higher-order nonlinear Schrödinger equation, which describes the propagation of pulses in optical fibres.     

(S)-stereoisomer of telomestatin as a potent G-quadruplex binder and telomerase inhibitor

Total synthesis of the (S)-stereoisomer of telomestatin (1) was accomplished. (S)-Telomestatin exhibited potency four times that of the natural product, (R)-telomestatin, which was the most potent telomerase inhibitor previously reported. In the circular dichroism spectral analysis of the complexes possessing randomly structured single-stranded d[TTAGGG](4) oligonucleotide, (S)-telomestatin, like (R)-telomestatin, induced an antiparallel G-quadruplex structure. The melting temperature (T(m)) value of the (S)-isomer complex was greater than that of the (R)-telomestatin complex. Therefore, it is concluded that the stereochemistry of the thiazoline of telomestatin is important to the binding ability of a G-quadruplex binder, and (S)-telomestatin as a G-quadruplex binder is more potent than the natural product.