Solid-phase synthesis of 2,3-diphenylpropionic acid library as VLA-4 antagonists

2,3-Diphenylpropionic acid library for VLA-4 antagonist was synthesized on solid-phase. Comparison of the two synthetic routes via an orthogonal generation of two aromatic amino functional groups are discussed. From this work, several compounds were identified as potent VLA-4 antagonists.     

Solution structure of S-DNA formed by covalent base pairing involving a disulfide bond

Here, we present the solution structure of a DNA duplex containing a disulfide base pair (S-DNA). The unnatural nucleoside "S" possessing a thiophenyl group as base was incorporated into a self-complementary singled-stranded oligonucleotide. Crosslinking of the disulfide base pair was analyzed by non-denaturing polyacrylamide gel electrophoresis. Under oxidizing conditions a high molecular weight band as 18 mer, corresponding to the double-stranded molecule (5'-GCGASTCGC: 3'-CGCTSAGCG), was found, whereas single-stranded self-complementary 9 mer oligonucleotide GCGASTCGC was detected in the presence of a reducing agent. These results suggest that the oligonucleotide is covalently linked by disulfide bonding under oxidizing conditions, which can be reversibly reduced to two thiol groups under reducing conditions. CD spectrum of S-DNA (CGASTCG) under oxidizing conditions suggested that the duplex had a right-handed double-stranded structure similar to that of natural DNA (B-form, CGATCG). NMR studies confirmed that this CGASTCG resembled natural B-DNA and that the two phenyl rings derived from the disulfide base pairing intercalated into the duplex. However, these two phenyl rings were not positioned in the same plane as the other base pairs. Specifically, NOEs suggest that although CGASTCG adopts a structure similar to B-type DNA, the S-DNA duplex is bent at the point of disulfide base pairing to face the major groove.     

A novel measurement method of Donnan potential at an interface between a charged membrane and mixed salt solution

We developed a novel measurement method of the Donnan potential difference at a charged membrane/salt solution interface. The method can measure the potential under the condition that the membrane charge density is much lower than the KCl concentration of the salt bridge. This method is very useful for obtaining the effective charge density of each layer of a bipolar membrane. The present experiments in a system of a negatively charged poly(vinyl alcohol) membrane and a single salt solution of KCl, NaCl, LiCl, CaCl₂ and LaC₃ revealed that the membrane effective charged density has the same value for all the ions. The experiments in mixed KCl and CaCl₂ solution revealed that the potential in the system is governed mainly by the concentration of the counterion having the highest valence in the system.     

Palladium(O)-catalyzed allylic alkylation and amination of allylic phosphates

Allyl diethyl phosphates (1) can be easily substituted with malonates and amines in the presence of palladium(O) catalyst. Synthetic utility of the reaction is demonstrated by the sequential amination-amination and alkylation-amination of (Z)-4-acetoxybut-2-enyl diethyl phosphate (1b) with high regio- and stereoselectivity.     

Oxidation of Dimethyl Sulfide in Air Using Electron-Beam Irradiation,and Enhancement of its Oxidation Via an MnO<Subscript>2</Subscript> Catalyst

The decomposition of dimethyl sulfide (DMS) at initial concentrations of 4.5–18.0 ppmv in air was studied under electron-beam (EB) irradiation. Doses to decompose 90% of input DMS were 2.5 kGy for 4.5 ppmv, 3.4 kGy for 10.6 ppmv, and 3.9 kGy for 18.0 ppmv. HCOOH, (CH₃)₂SO, and trace CH₃OH and (CH₃)₂SO₂ were produced as irradiation products in addition to CO₂ and CO. Application of an O₃ decomposition catalyst to an irradiated sample gas led to an enhancement in the oxidation of DMS and its products into CO₂ and the decomposition of O₃. For 10.6 ppmv DMS/air, the mineralization ratio increased from 41% via only EB irradiation to 100% via the combination treatment at 6.3 kGy. The yield of CO₂ to CO_x increased from 5.3 to 87.6% by combination with catalytic oxidation. This combination treatment enables the irradiation energy used to deodorize gas streams containing DMS to be reduced.     

Finite-Difference Time-Domain Analysis of the Interaction of Gaussian Evanescent Light with a Single Dielectric Sphere or Ordered Dielectric Spheres

The interaction of gaussian evanescent light with a single dielectric sphere or ordered dielectric spheres in an attenuated total reflection (ATR) geometry was analyzed by the finite-difference time-domain method. Various aspects of this interaction were investigated in terms of spatial visualizations of light intensity, reflectance vs. wavelength characteristics, the transient behavior of reflectances, and so forth. In the case of a single sphere, it was evident that the whispering gallery mode can be excited in ATR geometries, but such excitation cannot be easily confirmed only through the observation of wavelength-scanned ATR spectra. In the case of a closely packed two-dimensional array of dielectric spheres, it was found that an easy axis and also a difficult axis for light propagation exist.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Phisics and Mombusho Grantin Aid for Scientific Research on Priority Areas “Near-field Nano-optics” Project, sponsored by Japan Society for the Promotion of Science.