Efficient h/d exchange reactions of alkyl-substituted benzene derivatives by means of the Pd/C-H(2)-D(2)O system

A method for efficient and extensive H/D exchange of substituted benzene derivatives which is catalyzed by heterogeneous Pd/C in D(2)O as a deuterium source under hydrogen atmosphere is described. Multi-deuterium incorporation into unactivated linear or branched alkyl chains that bear a carboxyl, hydroxyl, ether, ester, or amide moiety and are connected with a benzene ring was achieved by using the Pd/C-H(2)-D(2)O system. The present method does not require expensive deuterium gas or any special equipment.     

Colle-Salvetti-type correction for electron-nucleus correlation in the nuclear orbital plus molecular orbital theory

A Colle-Salvetti (CS)-type electron-nucleus correction in the nuclear orbital plus molecular orbital theory is proposed. The CS-type correction is designed to satisfy the cusp condition for the electron-nucleus interaction. Since the CS-type correction is expressed in terms of the electron and nucleus densities, its evaluation is computationally feasible. Numerical assessment confirms that the CS-type correction performs well for the small G2 set.     

Preparation of Mitochondria- and Epigenetics-Targeting Nanoparticles for Suppression of Cancer Metastasis

Epithelial-to-mesenchymal transition (EMT) of carcinoma cells is a promising target for cancer therapy since it is closely related to tumor metastasis and therapeutic resistance. The process of EMT is strongly associated with epigenetic alterations in cancer cells. In addition, recent accumulating evidence suggests that EMT also has a significant influence on inducing cancer stem cells (CSCs). In this study, novel polymer core–lipid shell nanoparticles (PLNPs) are prepared to suppress cancer EMT by the combined effects of the antioxidant activity of core-encapsulated Mn imidazolium porphyrin (MnImP) and the epigenetic control by histone acetyltransferase-encoding plasmid DNA (pHAT) hybridized onto the shell surface. PLNPs show the ability to control the expression of EMT-related markers, resulting in the suppression of EMT in lung epithelial cancer cells (paraquat-treated A549 cells). Furthermore, PLNPs suppress the levels of intracellular mitochondrial ROS and the transformation to CSCs. The results of this study may provide a novel therapeutic strategy against tumor metastasis and treatment resistance.     

Large-Scale Preparation of N,N'-Diacetylchitobiose by Enzymic Degradation of Chitin and its Chemical Modifications

Abstract

Hundred gram quantities of peracetylated chitobiose were prepared by degradation of colloidal chitin with commercially available chitinase (EC 3.2.1.14) from Streptomyces griseus and subsequent acetylation, the product being readily convertible into N, N'-diacetylchitobiose by conventional de-O-acetylation. These chitobiose derivatives were subjected to further chemical modifications to give novel disaccharide derivatives composed of a pair of 2-acetamido-2-deoxy-D-allopyranose moieties that are potential intermediates for the synthesis of an enzyme inhibitor.     

Gas transport properties of asymmetric polyimide membranes prepared by plasma‐based ion implantation

In this study, we report the gas permeance and selectivity of the asymmetric polyimide membrane prepared by plasma‐based ion implantation (PBII). The asymmetric polyimide membranes were prepared using a dry–wet phase inversion process, and the surface skin layer on the membrane was implantated by He ions at 2.5 keV. The asymmetric membranes treated by PBII were measured using a high vacuum apparatus with a Baratron absolute pressure gauge at 76 cmHg and 35°C. The (O₂/N₂) and (CO₂/CH₄) selectivities in the He⁺‐implanted asymmetric membrane at 60 sec resulted in 1.5 and 1.8 time increases, respectively, when compared to those of the asymmetric membrane before PBII. On the other hand, the O₂ and CO₂ permeances in the asymmetric membrane after PBII decreased with an increase in the He⁺ treatment time. In this paper, we addressed, for the first time, the gas permeation behavior of the asymmetric polyimide membranes prepared by PBII. Copyright © 2009 John Wiley & Sons, Ltd.     

Study of types and mixture ratio of organic solvent used to dissolve polymers for preparation of drug-containing PLGA microspheres

The effects of the types and the ratios of various organic solvents used as a mixtures to dissolve poly (lactide-co-glycolide) (PLGA) by using a solvent evaporation method, a technique used to prepare polymer particles, were carefully studied in order to investigate their advantages in developing drug delivery system (DDS) formulations for the prepared microspheres. The particle size and drug loading efficiency of drug-containing PLGA microspheres were found to be dependent on the types of solvent used due to the interfacial tension between the organic solvent and water phase. The drug loading efficiency of monodisperse microspheres prepared by using a membrane emulsification technique employing organic solvents and high interfacial tension for dissolving the PLGA was increased in a controlled manner. The organic solvents with high interfacial tension in the water phase used for the preparation of polymer particles by means of the solvent evaporation method were found to be suitable in terms of improvement in the properties of DDS formulations.     

Selective cleavage of primary MPM ethers with TMSI/Et3N

A useful method for the selective cleavage of primary MPM ethers by using TMSI/Et₃N is described. Other protective groups such as secondary MPM ethers, silyl ethers, and benzylidene acetal were stable under the reaction conditions.     

Rhodium-catalyzed asymmetric coupling reaction of allylic ethers with arylboronic acids

An asymmetric allylic substitution of simple allylic ethers with arylboronic acids in the presence of a rhodium(I)/(R)-DTBM-SEGPHOS catalyst has been developed. The reactions proceeded smoothly at room temperature to give the corresponding branch products with excellent regioselectivities and good to excellent enantioselectivities.     

Design of NIR-absorbing simple asymmetric squaraine dyes carrying indoline moieties for use in dye-sensitized solar cells with Pt-free electrodes

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.5G) with an incident photon-to-current conversion efficiency of 63% (650 nm), a short-circuit photocurrent density of 13.64 mA, an open-circuit photovoltage of 0.48, and a fill factor of 0.57.     

Improved synthesis of the A-G ring segment of brevetoxin B

An efficient synthesis of the A-G ring segment 2, a key intermediate for the total synthesis of brevetoxin B (1), was achieved in 37 steps and 5.0% overall yield. The intramolecular allylation of the O,S-acetal 22, prepared from the ABC ring segment 15 and the FG ring segment 17, was carried out using AgOTf as a Lewis acid to give the desired compound 23, predominantly. Ring-closing metathesis of 23 with the Grubbs catalyst 12 afforded the heptacyclic ether 25. Selective hydrogenation of the E ring olefin of 25 was performed by diimide reduction to afford 2.