An attempt directed toward enhanced shape selectivity in reversed-phase liquid chromatography: preparation of the dodecylaminated beta-cyclodextrin-bonded phase.

With the aim of preparing a stationary phase with a high shape-recognition ability for liquid chromatography, a new bonded phase was synthesized by coupling multiply dodecylamino-substituted beta-cyclodextrin (beta-CD) to 3-glycidoxypropyl-derivatized silica gel. The stationary phase prepared in this way was expected to have increased shape selectivity compared with that of conventional reversed-phase materials, due to solute interactions with the alkyl chain piles built up on the beta-CDs bonded to silica. The separation characteristics of the bonded phase were investigated using polycyclic aromatic hydrocarbons (PAHs) with different molecular shapes and compared with those of monomeric ODS and native beta-cyclodextrin-bonded phases. The newly developed stationary phase was found to be highly selective for PAHs.     

Rod-like liquid crystals of organic transition metal complexes. I. Reversible transformation between blue smectogen and red nematogen

Two novel types of transition-metal-containing liquid crystals, bis(p-n-koxydithiobenzoato)nickel(II) (abbreviated as (C_nO-DTB)₂Ni), and (p-n-alkoxydithiobenzoato)(p-n-alkoxyperthiobenzoato)nickel(II) (abbreviated as (C_nO-DTB)(C_nO-PTB)Ni), were synthesized. It was found that the (C_nO-DTB)₂Ni complex for n = 8 has smectic H and C mesophases, and that the (C_nO-DTB)₂Ni complexes for n = 4 and 8 easily transform into the corresponding monoperthio complexes, _nO-PTB)Ni, by heating at temperatures between 230°C and 285°C. It was confirmed that the transformation originates from an intermolecular reaction between the (C_nO-DTB)₂Ni complexes at high temperatures, and that the origin of the extra sulphurs in the resulting (C_nO-DTB)(C_nO-PTB)Ni complexes is the neighbouring (C_nO-DTB)₂Ni complexes. Interestingly, each of the (C_nO-DTB)(C_nO-PTB)Ni complexes (n = 4 and 8), has nematic mesophase and exhibits a unique double melting behaviour via the nematic phase, which is the first example in liquid crystals. The reversible transformation between the blue smectic rod-like (C_nO-DTB)₂Ni complex and the red nematic Λ-like (C_nO-DTB)(C_nO-PTB)Ni complex is possible.     

Reactions of lithium tributyl heteroaryl borates with allylic bromides in the presence of copper(I) cyanide

The reaction of various lithium tributylheteroarylborates with allylic bromides in the presence of copper(I) cyanide furnished the regioselective allylation at the heteroaryl ring.     

Protective effects of various Chinese traditional medicines against experimental cholestasis

In a previous paper, we reported that methanol extracts obtained from 13 Chinese traditional medicines showed remarkable choleretic effects in normal rats. This paper examines the protective effects against experimental cholestasis induced by carbon tetrachloride (CCl4) or alpha-naphthylisothiocyanate (ANIT) in rats. No medicines, including sodium dehydrocholate and 1-phenylpropanol which are used clinically as choleretic drugs, inhibited the decrease of bile flow induced by CCl4. On the other hand, Intinko-to, Saiko-seikan-to and Bohu-tusyo-san revealed marked improvement of the dysfunction in bile secretion induced by ANIT. These three medicines inhibited the decrease of excretion of bile acid or bilirubin in the bile. They also exerted a protective effect against the alterations of serum components induced by ANIT, i.e., of glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, alkaline phosphatase and the concentration of serum bilirubin. These results indicate that methanol extracts of Intinko-to, Saiko-seikan-to and Bohu-tusyo-san demonstrate not only choleretic effects but also improvement of cholestasis and liver parenchymal injury in rats.     

Stereoselective synthesis of trans olefins by the reaction of Wittig reagents with selenium. Formation of selenocarbonyl compounds.

Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium. The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction.     

New Magneto-Optical Effect in Co-Doped CuGeO3

We report the anomalous effect of the polarization dependence of electron paramagnetic resonance absorption in CuGeO₃ doped with 2% of Co. While the resonance line of Cu²⁺ chains is independent of the microwave polarization in the Faraday geometry, the resonant mode of Co impurity exhibits a strong polarization dependence for all directions of the external magnetic field. Possible reasons of such behavior are discussed. Authors' address: Alexey V. Semeno, Department of Low-Temperature and Cryogenic Engineering, A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Vavilov ulitsa 38, Moscow 119991, Russian Federation