A solid-supported acidic oxazolium perchlorate as an easy-handling catalyst for the synthesis of modified pyrimidine nucleosides via Vorbrüggen-type N-glycosylation

A solid-supported acidic oxazolium perchlorate was investigated as a heterogeneous catalyst in N-glycosylation reactions using silylated modified pyrimidines and an acylated ribose or glucose to afford the corresponding pyrimidine nucleosides. This salt is a nonhygroscopic and stable powder whose activity is comparable to that of 2-methyl-5-phenylbenzoxazolium perchlorate. A reaction with this polymer catalyst can be conducted on a gram scale. Reusability of the solid-supported catalyst was also investigated.     

The almost alternating diagrams of the trivial knot

Bankwitz characterized the alternating diagrams of the trivialknot. A non-alternating diagram is called almost alternatingif one crossing change makes the diagram alternating. We characterizethe almost alternating diagrams of the trivial knot. As a corollary,we determine the unknotting number one alternating knots withthe property that the unknotting operation can be done on itsalternating diagram. Received July 3, 2007. Revised September 29, 2008.     

Stereoselective one-pot preparation of 1,2,4,5-tetraalkylidene- and 1,4-dialkylidenecyclohexanes

1,2,4,5-Tetraalkylidene- and 1,4-dialkylidenecyclohexanes were prepared by the regio- and stereoselective homocoupling of skip-type diynes and enynes, and their Diels-Alder reaction to form a polycyclic compound was demonstrated.     

Holographic reconstruction with a 10- mum pixel-pitch reflective liquid-crystal display by use of a light-emitting diode reference light

We reconstructed an animation made from computer-generated holograms with a reflective LCD panel that had a pixel pitch of 10 mumx10 mum and resolution of 1400x1050 . Using a LED as the reference light, we could clearly observe three-dimensional images whose size was approximately 30 mmx10 mm x30 mm . Moreover, we reconstructed a color holograph by use of a simple system with a set of red, green, and blue LEDs as the reference light.     

Structure and synthesis of a new hypotensive vasodilator isolated from Streptomyces aureofaciens

The structure elucidation and synthesis of WS-1228 A, produced by $\text{Streptomyces aureofaciens}$, were described.     

Selective oxidation of hydroxy groups of phenylthio and phenylseleno alcohols

Various kinds of alcohols bearing phenylthio or phenylseleno moiety were converted into the corresponding carbonyl compounds in good to excellent yields by treating with dimesityl diselenide and $\text{tert}$-butyl hydroperoxide.     

Production of doubly charged helium ions by two-photon absorption of an intense sub-10-fs soft x-ray pulse at 42 eV photon energy

We report on the observation of doubly charged helium ions produced by a nonlinear interaction between a helium atom and photons with a photon energy of 42 eV which are generated with the 27th harmonic of a femtosecond pulse from a Ti:sapphire laser. The number of ions is proportional to the square of the intensity of the 27th harmonic pulse, and thus two-photon double ionization should be dominantly induced as compared with other nonlinear processes accompanying sequential ionization via a singly charged ion. This phenomenon is utilized to measure the pulse duration of the 27th harmonic pulse by using an autocorrelation technique, for the first time to our knowledge, and as a result a duration of 8 fs is found.     

Chaotic itinerancy in the oscillator neural network without Lyapunov functions

Chaotic itinerancy (CI), which is defined as an incessant spontaneous switching phenomenon among attractor ruins in deterministic dynamical systems without Lyapunov functions, is numerically studied in the case of an oscillator neural network model. The model is the pseudoinverse-matrix version of the previous model [S. Uchiyama and H. Fujisaka, Phys. Rev. E 65, 061912 (2002)] that was studied theoretically with the aid of statistical neurodynamics. It is found that CI in neural nets can be understood as the intermittent dynamics of weakly destabilized chaotic retrieval solutions.