Reaction of carboxamide with Cu2Oisonitrile complex; formation of a new chelated copper(I) complex

Reaction of carboxamides with Cu₂O in the presence of t-butyl isocyanide gave new chelated copper(I) complexes, which probably are formed by the insertion of t-butyl isocyanide into the coppernitrogen bond of copper(I) amide isonitrile complexes, which were initially produced from the carboxamides and Cu₂Ot-butyl isocyanide complex. The same chelated copper(I) complexes were prepared more readily by the reaction of the corresponding N-trimethylsilyl-carboxamides with Cu₂Ot-butyl isocyanide complex. Reactions of the copper(I) complexes thus obtained with alkylating agents, such as alkyl halides, alkyl tosylates and triethyloxonium tetrafluoroborate, also were described.     

Enantioselective addition of ketene silyl acetals to nitrones catalyzed by chiral titanium complexes. Synthesis of optically active beta-amino acids

A chiral titanium complex, Ti(O-i-Pr)(4)/BINOL/tert-butylcatechol, catalyzes enantioselective addition reaction of ketene silyl acetals to nitrones to give optically active beta-amino acid derivatives which are biologically active compounds and useful synthetic intermediates of natural products and pharmaceuticals such as beta-lactam antibiotics. The combined process of catalytic oxidation of secondary amines and enantioselective carbon-carbon bond formation of nitrones thus obtained with ketene silyl acetals provides a useful two-step method for the synthesis of optically active beta-amino acid derivatives and related nitrogen compounds.     

Novel efficient preparative method for phthalocyanines from phthalimides and phthalic anhydride with HMDS

A convenient synthesis of peripherally substituted or unsubstituted phthalocyanines having a variety of metals is described. Phthalocyanines can be obtained by heating phthalimides or phthalic anhydride with metal salts, hexamethyldisilazane, a catalytic amount of p-TsOH, and DMF at 150 degrees C.     

Depolymerization of poly(2,6-dimethyl-1,4-phenylene oxide) under oxidative conditions

Depolymerization of an engineering plastic, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), was accomplished by using 2,6-dimethylphenol (DMP) under oxidative conditions. The addition of an excess amount of DMP to a solution of PPO in the presence of a CuCl/pyridine catalyst yielded oligomeric products. When PPO (M(n)=1.0x10(4), M(w)/M(n)=1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to M(n)=4.9x10(2) (M(w)/M(n)=1.5). By a prolonged reaction with the oxidant, the oligomeric product was repolymerized to produce PPO essentially identical to the starting material, making the oligomer useful as a reusable resource. During the depolymerization reaction, an intermediate phenoxyl radical was observed by ESR spectroscopy. Kinetic analysis showed that the rate of the oxidation of PPO was about 10 times higher than that of DMP. These results show that a monomeric phenoxyl radical attacks the polymeric phenoxyl to induce the redistribution via a quinone ketal intermediate, leading to the substantial decrease in the molecular weight of PPO, which is much faster than the chain growth.     

Slipping of a histidine improved the peroxidase activity of a de novo designed polypeptide packing an iron porphyrin

Polypeptides with two histidines and an iron porphyrin (1H⁴⁰-7H⁴⁶) were synthesized with a variety of positions of a histidine. In 4H⁴³, histidine (H⁴³) was in the hydrophobic region of an α-helix. The other polypeptides were of slightly or substantially distorted conformation. In the pH 7.2 buffer solution, two histidines of the polypeptide coordinated the iron porphyrin regardless of their positions. Some polypeptides (1H⁴⁰, 3H⁴², and 5H⁴⁴) showed an enhanced catalytic activity in the peroxidase reaction using cumene hydroperoxide compared to that of 4H⁴³, whereas some polypeptides (2H⁴¹ and 6H⁴⁵) were ineffective catalysts. The distortion of the peptide conformation by the addition of MeOH was also effective for the peroxidase reaction.     

Output and picosecond amplification characteristics of an efficient and high-power discharge excimer laser

Improvements in output pulse energy and efficiency of a conventional capacitor-transfer-type discharge excimer laser with automatic preionization have been achieved by extending the discharge volume and resulting moderate pumping of the active medium. The discharge laser produces a pulse energy of more than 1 J for XeCl, KrF, and ArF lasers in square beams of about 2×2 cm², and the maximum overall efficiency observed is 2.9% for XeCl, 3.2% for KrF and 1.8% for ArF. The laser device has been involved in a picosecond ( 32 ps) XeCl laser amplification system, and was operated as an amplifier at a repetitive frequency of 10 Hz. Saturation fluence for XeCl laser was measured to be 1.4 mJ/cm², and the picosecond pulse energy of 40 mJ was extracted from the amplifier.On leave from Ebara Corp., 6-6-7, Ginza, Chuo-ku, Tokyo 104, JapanOn leave from Mitsubishi Heavy Industries, LTD., 4-6-22, Kan-on shinmachi, Nishi-ku, Hiroshima 733, Japan     

PHOTOCHEMICAL REACTION OF 13-CIS-BACTERIORHODOPSIN STUDIED BY LOW TEMPERATURE SPECTROPHOTOMETRY

Abstract— The photoreaction cycle of 13- cis -bacteriorhodopsin (13- cis -bR) was investigated by low temperature spectrophotometry using two different preparations; 13- cis -bR constituted from bacterioopsin and 13- cis -retinal, and dark-adapted bacteriorhodopsin (bR^D), which is an equi-molar mixture of 13- cis -bR and trans -bR.
By irradiation with 500 nm light at — 190°C, 13- cis -bR was converted to its batho-product, batho-13- cis -bR (batho-bR¹³), which is different from batho-product from trans -bR, batho-bR^t. On warming batho-bR¹³ to -5°C in the dark, it completely changed to trans -bR. We estimated the composition of 13- cis -bR and trans -bR in the warmed sample spectrophotometrically and then the absorption spectrum of batho-bR¹³ was calculated. The absorption maximum lies at 608 nm, 1250 cm⁻¹ longer than that of 13- cis -bR; the molar extinction coefficient (ε) is about 74000 M ⁻¹ cm⁻¹, larger than that of 13- cis -bR (52000 M ⁻¹ cm⁻¹).
On the warming the sample containing batho-bR¹³ formed by irradiating 13- cis -bR or bR^D at — 190°C, we could not detect other intermediates such as the lumi- or meta-intermediates seen in trans-bR system.     

Recent progress in the improvement of hydrothermal stability of zeolites

Zeolites have been successfully employed in many catalytic reactions of industrial relevance. The severe conditions required in some processes, where high temperatures are frequently combined with the presence of steam, highlight the need of considering the evolution of the catalyst structure during the reaction. This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.

This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.     

On-line purification for the determination of catecholamines by liquid chromatography

An on-line purification method for catecholamines was studied using a flow system equipped with an alumina microcolumn. The procedure involves catecholamine adsorption, column washing and catecholamine elution steps. The system is designed not to decompose catecholamines under alkaline conditions in the adsorption step. Flow-rates and times for different solutions delivered in each step (alkaline buffer for adsorption, water for washing and an acidic solution for elution), column length and sample volume to be loaded were systematically investigated by liquid chromatography. Under optimum conditions, norepinephrine, epinephrine, dopamine and 3,4- dihydroxybenzylamine (internal standard) can be purified with recoveries of ? 90% within 11 min with manual operation. This method was efficiently applied to urine samples and the results indicate the possibility that catecholamines in biological samples are automatically purified.