Synthesis of fluspidine via asymmetric NaBH4 reduction of silicon enolates of β-keto esters

Asymmetric NaBH₄ reduction catalyzed by the Co(II) complex of a chiral diamidine-type sp²N ligand, Naph-diPIM-dioxo-iPr, was successfully applied to 3-silyloxycinnamate substrates without over-reduction, giving quantitatively 3-silyloxy-3-arylpropionates with an enantiomer ratio of up to 99:1. The high utility was confirmed on a 30-g scale using 0.1?mol% catalyst. Both Z and E substrates could be converted to a single enantiomeric product by changing the ligand chirality. The relationship between the Z/E stereochemistry and the absolute configuration of the 1,4-reduction product provided important information about the mechanism underlying enantioface selection. Combination of the asymmetric catalysis with two other key steps, Suzuki coupling with an N-protected tetrahydropyridine boronic acid derivative and intramolecular bromo etherification, realized an efficient synthetic route to both enantiomers of fluspidine. The new strategy permits the introduction of substituents on the two aryl groups and piperidine ring, allowing for structural variations toward the development of higher performance σ1 receptor antagonists.     

High quality a-Si film produced by horizontal plasma furnace

A series of investigation on the a-Si film quality in a p-i-n junction has been made by employing the separated three chamber system of horizontal plasma mode. A clear improvement of film quality has been experimentally verified in a-Si films prepared by this system as compared with those by the single chamber system. On the basis of these investigation, a-SiC/a-Si/μc-Si heterojunction solar cells having more than 9% conversion efficiency have been developed.     

Novel synthesis of conjugated dienes attached to a quaternary carbon center via Pd(0)-catalyzed deconjugative allylation of alkenylidenemalonates

Palladium(0)-catalyzed deconjugative allylation of alkenylidenemalonates and alkylidenemalonates was achieved for the first time. Reactions of dimethyl 2-((E)-but-2-enylidene)malonate with various allylic acetates using LHMDS as a base in DMF in the presence of Pd(2)dba(3) (2.5 mol %) and PPh(3) (10 mol %) proceeded at room temperature to give the corresponding alpha-allylation products in good yields in a regio- and stereoselective manner. This reaction can also be used for allylation of dimethyl ethylidenemalonate or dimethyl 2-((E)-pent-2-enylidene)malonate and give the desired alpha-allylation products in good yields.     

Interaction between dyes and polyelectrolytes. XI. Photoreduction of methylene blue bound to potassium polystyrenesulfonate

The effect of potassium polystyrenesulfonate (PSSK) on the quantum yield (Φ) in the photoreduction of methylene blue (MB) by allylthiourea was investigated. MB was bound to PSSK in monomeric, dimeric, or slightly aggregated form, depending on the polyanion–dye ratio (P/D). At a relatively lower P/D in which most MB molecules were bound to PSSK in dimeric or slightly aggregated form, the value of Φ was smaller than that at a P/D of zero. On the other hand, at a higher P/D, in which most MB molecules were bound to PSSK in monomeric form, the value of Φ was larger than that at a P/D of zero. It was suggested that the lower reactivity of dimeric or slightly aggregated MB on PSSK was caused by the length of its lifetime which is shorter than that of the monomeric form. It was also suggested that the increase in Φ at higher P/D was caused by the decreased deactivation of the triplet excited MB by the ground-state MB.     

Effect of laser supported detonation wave confinement on termination conditions

A laser supported detonation (LSD) wave was driven using line-focusing laser optics, in which an induced blast wave expanded laterally from the LSD region to surrounding air in two-dimensional space. The LSD wave was confined in quasi-1D space using a wedge nozzle to restrict the lateral expansion of a blast wave. The LSD termination threshold and the blast wave energy were deduced from shadowgraphs showing the blast wave expansion. The respective threshold laser intensities for cases with and without confinement were estimated as 17 and 34 GW/m², indicating that the lateral expansion strongly influenced on the LSD termination condition.      

Asymmetric borane reduction of ketones catalyzed by N‐hydroxyalkyl‐l‐menthopyrazoles

The equimolar mixture of N‐(hydroxyalkyl)pyrazoles and borane formed boric ester complex, in which the remaining borane was stabilized by the adjacent nitrogen of thr pyrazole ring. The borane complex derived from the chiral pyrazoles such as 3‐phenyl‐l‐menthopyrazole reduced p‐methylacetophenone ( 21 ) enantioselectively. When (2′S)‐2‐(2′‐phenyl‐2′‐hydroxyethyl)‐3‐phenyl‐l‐menthopyrazole ((2′S)‐ 10b ) was used, 21 was reduced into (S)‐p‐methylphenyl‐1‐ethanol ( 22 ) in moderate chemical and optical yields. Due to the inconvenience of the preparation and the lower optical yield, the use of N‐(α‐hydroxyalkyl)pyrazoles was unpromising for the enantioselective reduction of ketones by borane.     

Freeze-fracture electron microscopic and calorimetric studies on microscopic states of surface-modified liposomes with poly(ethylene glycol) chains

The differential scanning calorimetry (DSC) and the freeze-fracture electron microscopy of dipalmitoyl phosphatidylcholine (DPPC) liposomes containing distearoyl-N-monomethoxy poly(ethylene glycol)-succinyl-phosphatidylethanolamines (PEG-DSPE) were carried out. The DSC peak of DPPC liposomes containing PEG-DSPE had a shoulder. The main phase transition temperature of DPPC bilayer membranes containing PEG-DSPE whose molecular weight of PEG is less than 3000 was slightly shifted to a higher temperature, while that containing PEG-DSPE whose molecular weight of PEG is more than 5000 was slightly shifted to a lower temperature. The electron micrographs of freeze-fracture replicas of DPPC liposomes containing PEG-DSPE quenched from 37±2°C exhibited banded and planar textures, suggesting the lateral phase separation in the bilayer membranes.     

Finite-size-scaling analyses of the chiral ordert in the Josephson-junction ladder with half a flux quantum per plaquette

Chiral order of the Josephson-junction ladder with half a flux quantum per plaquette is studied by means of the exact diagonalization method. We consider an extreme quantum limit where each superconductor grain (order parameter) is represented by S=1/2 spin. So far, the semi-classical case, where each spin reduces to a plane rotator, has been considered extensively. We found that in the case of S=1/2, owing to the strong quantum fluctuations, the chiral (vortex lattice) order becomes dissolved except in a region, where attractive intrachain and, to our surprise, repulsive interchain interactions both exist. On the contrary, for considerably wide range of parameters, the superconductor (XY) order is kept critical. The present results are regarded as a demonstration of the critical phase accompanying chiral-symmetry breaking predicted for frustrated XXZ chain field-theoretically. Received 20 February 2000     

Optical Properties and Photopolymerization of Liquid Crystalline (Acetyl) (Ethyl) Cellulose/Acrylic Acid System

The structure and properties of a chiral nematic phase, which reflects one hand of circularly polarized light in a narrow region of wavelength, of fully acetylated (ethyl) cellulose [(acetyl) (ethyl) cellulose, AEC] in acrylic acid (AA) were studied in comparison with (ethyl) cellulose (EC). AEC mesophase formed right-handed chiral nematic structure while EC formed left-handed one. AEC mesophase showed higher birefringence and reflection intensity. The relationship between the reflection wavelength and the polymer concentration was negatively correlated for both AEC and EC mesophases. The relationship between the reflection wavelength and the molecular weight was also negative for AEC mesophase whereas positive for EC mesophase. AEC mesophase was solidified by photopolymerization of AA moiety. It was revealed that the optical properties of AEC mesophase could be preserved by photopolymerization, since the resulting solid material reflects selectively one hand of circularly polarized light.