Chiral ligand exchange capillary electrophoresis using borate anion as a central ion

Native DL-pantothenic acid, having a 1,3-diol structure, was chirally resolved by ligand exchange capillary electrophoresis using (S)-3-amino-1,2-propanediol as a chiral selector and the borate anion as a central ion. The optimum conditions for both high resolution and short migration time of DL-pantothenic acid were found to be 200 mM (S)-3-amino-1,2-propanediol and 200 mM borate buffer (pH 9.2) containing 15% methanol with an applied voltage of +25 kV at 20 degrees C, using direct detection at 200 nm. With this system, the resolution (Rs) of racemic pantothenic acid was approximately 1.7. When (S)-1,2-propanediol, (S)-1,2,3-propanetriol, (S)-1,3-butanediol or (S)-1-amino-2-propanol were used as chiral ligand instead of (S)-3-amino-1,2-propanediol, DL-pantothenic acid was not enantioseparated. When borate was replaced with Tris or butylborate, no chiral separation was achieved. Therefore, the ionic interaction between the amino and carboxyl groups of the ternary complex may play an important role in the enantioseparation of DL-pantothenic acid by the proposed CE system.     

A simple method removing 2-oxazolidinone and 2-hydroxyethylamine auxiliaries in methoxide-carbonate systems for synthesis of planar-chiral nicotinate

A facile and practical removal of 2-oxazolidinone and 2-hydroxyethylamine auxiliaries was accomplished by treating the corresponding N-acyl-2-oxazolidinone and N-(2-hydroxyethyl)amide derivatives in simple methoxide-carbonate systems. The presence of excess DMC (dimethyl carbonate) accelerates the N-acyl bond cleavage for those substrates under mild reaction conditions, and the present method was found to be useful especially for the synthesis of planar-chiral nicotinate.     

Unperturbed dimensions of polystyrene derivatives. II. Poly-3,4-dichlorostyrene and poly-p-cyclohexylstyrene

The relationship of intrinsic viscosity to the number-average molecular weight has been obtained for poly-3,4-dichlorostyrene and poly-p-cyclohexylstyrene in a few solvents. Values of (〈L²〉₀/M)^1/2 have been estimated for poly-3,4-dichlorostyrene and poly-p-cyclohexylstyrene through the use of the treatment of Stockmayer and Fixman. The values of (〈L〉₀/M)^1/2 have been obtained as 2.18 ± 0.08 and 2.52 ± 0.07 for poly-3,4-dichlorostyrene and poly-p-cyclohexylstyrene, respectively. The σ value of a series of polystyrene derivatives has been found to increase with the bulk of side groups. This seems to indicate that the σ value is mainly determined by the steric repulsion between side groups.     

The behavior of water molecules in semi-crystalline bilayer structure of phosphatidylethanolamine

The crystalline phase of dimyristoylphosphatidylethanolamine (DMPE)-water system was obtained by annealing the gel phase at around ?5°C for periods up to 30 days. It was investigated by differential scanning calorimetry and negative-stain electron microscopy, particularly focusing on the behavior of water molecules. The crystalline phase showed a two-dimensional ribbonlike structure composed of regularly-stacked lamellae with an interlamellar spacing narrower than that of the gel phase. The conversion of the gel to crystalline phases on annealing was accompanied by a change in the bonding model of water molecules from a loosely-bound interlamellar water to a more loosely-bound water outside the lamellae. Ice-melting curves were deconvoluted using a computer program and different structures of water were estimated from enthalpy changes of each deconvoluted component. In accordance with a micrograph, only the loosely-bound water of one molecule of H₂O per lipid was shown to be located between lamellae of the crystalline phase.     

Protein boson peak originated from hydration-related multiple minima energy landscape

The boson peak is a broad peak found in the low-frequency region of inelastic neutron and Raman scattering spectra in many glassy materials, including biopolymers below approximately 200 K. Here, we give a novel insight into the origins of the protein boson peak, which may also be valid for materials other than proteins. Molecular simulation reveals that the structured water molecules around a protein molecule increase the number of local minima in the protein energy landscape, which plays a key role in the origin of the boson peak. The peak appears when the protein dynamics are trapped within a local energy minimum at cryogenic temperatures. This trapping causes very low frequency collective motions to shift to higher frequencies. We demonstrate that the characteristic frequency of such systems shifts higher as the temperature decreases also in model one-dimensional energy surfaces with multiple minima.     

Synthesis and DNA strand breakage activity of some 1,4-diazepines

Reactions of 1,3-propanediamine with alpha-dicarbonyl compounds (1a-e) were examined and various condensed heterocyclic compounds such as 1,4-diazepines (2) and 3-pyrimidine derivatives (3) were obtained. Some of 1,4-diazepines (2) showed DNA strand breakage activity.     

A novel palladium(0)-catalyzed addition of diphenyl disulfide to allenes leading to vicinal disulfides and its application to carbonylation with carbon monoxide

Tetrakis(triphenylphosphine)palladium(0) catalyzes a highly regioselective bisthiolation of terminal allenes with diphenyl disulfide to afford the corresponding 2-(phenylthio)-substituted allyl sulfides in good yields. In addition, this reaction system can be applied to the carbonylation under pressurized carbon monoxide.     

Development of a new traceless aniline linker for combinatorial solid-phase parallel synthesis of rod-shaped liquid crystals with an azomethine linkage

A new traceless linker was developed to synthesize a library of 28 compounds possessing an azomethine linkage using combinatorial solid-phase parallel synthesis. The loading of the substrates on a solid support and cleavage from the solid support were performed by an imine synthesis and by imine-exchanged process in the mild conditions, respectively. Products with a thioester group exhibited liquid crystalline properties with the higher transition temperatures than the others.     

Supramolecular architecture consisting of an enantiopure amine and an achiral carboxylic acid: application to the enantioseparation of racemic alcohols

Three-dimensionally dissymmetric cavities are created from an enantiopure amine and an achiral carboxylic acid, which can incorporate the third components to realize the formation of closely packed crystals. The combination demonstrates enantioselective inclusion for 20 kinds of racemic alcohols. The inclusion phenomenon occurs not only during crystallization but also in the solid state.