New process for producing cellulose acetate from wood in concentrated acetic acid

To explore further potential applications of acetic acid pulp, an investigation was conducted to develop a direct method for producing cellulose acetate from wood in combination with atmospheric acetic acid pulping. The process consists of delignification, totally chlorine-free bleaching, and esterification, with the concentrated acetic acid aqueous solution being used as only solvent throughout the process. The acetic acid pulp with kappa number of 30 and ISO brightness of 16 was bleached with 5% ozone on pulp to kappa number of 1.4 and brightness of 61. The resulting bleached pulp was further bleached with peracetic acid to kappa number of less than 1.0 and brightness of 68. The final bleached acetic acid pulp was acetylated with acetic anhydride in the concentrated acetic acid for 45 min to produce cellulose acetate with an apparent degree of substitution (DS) of 2.54. Although the product was lower grade compared with commercially available cellulose diacetate because it was prepared from the chemical pulp but not dissolving pulp, the product was almost soluble in acetone. Eventually, the DS of the acetone-soluble fraction was 2.62. The acetone solubility might be attributed to the original acetic acid pulp that had been partially acetylated during the pulping.     

Preparation and properties of ligand-free methylcopper and of copper alkyls coordinated with 2,2′-bipyridyl and tricyclohexylphosphine

A series of copper alkyls (methyl, ethyl and n-propyl) with ligands (2,2′-bipyridyl and tricyclohexylphosphine) and copper methyl without ligands has been prepared by the reaction of copper(II) acetylacetonate with dialkylaluminum monoethoxides in the presence or absence of the ligand in diethyl ether under nitrogen at low temperature. The copper alkyls were characterized by elemental analysis, chemical reactions, and by IR and NMR spectra. The ligand-free methylcopper is thermally very unstable and decomposed explosively; the bipyridyl ligand showed little effect on the stability of the copper alkyl. In contrast, the tricyclohexylphosphine-coordinated complexes are thermally very stable. Various reactions of the tricyclohexylphosphine-coordinated copper alkyls toward carbon dioxide, alkyl halides and olefins have been studied.     

Practical synthesis of optically active amino alcohols via asymmetric transfer hydrogenation of functionalized aromatic ketones

2-Substituted acetophenones such as 2-cyano-, 2-azido-, or 2-nitroacetophenones were effectively reduced with a mixture of HCOOH/N(C(2)H(5))(3) containing a chiral Ru(II) catalyst, RuCl[(S,S)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine](p-cymene), giving the corresponding optically active alcohols, which can be converted to optically active amino alcohols with excellent ee's. Similarly, the reaction of 2-benzoylacetophenone with the same Ru catalyst gave a quantitative yield of the corresponding optically active 1,3-diol with 99% ee.     

Accurate mass measurement in nano-electrospray ionization mass spectrometry by alternate switching of high voltage between sample and reference sprayers

An electrospray dual sprayer, which generates separate sample and reference sprays by alternately switching the high voltage between the two sprayers, is described. The technique permits accurate mass measurements in nano-electrospray ionization mass spectrometry (ESI-MS) to be obtained using a quadrupole/orthogonal acceleration time-of-flight mass spectrometer (Q-TOF). Similar to the method employed with a dual ESI source (Wolff JC et al., Anal. Chem. 2001; 73: 2605), the two sprays are orthogonal with respect to each other, but can be independently sampled without any baffle between these sprays. The reference sprayer is used in the original configuration of the ESI source and was optimized for a 1-2 muL/min flow, whereas the sample sprayer can be either a conventional glass capillary or a borosilicate tip of the type used for nano-ESI. Both sprayers can be positioned close to the cone so as to give maximum ion currents. The sample and reference sprays are independently generated by raising the potentials on the sample and reference sprayers to 1.4 and 3.0 kV, respectively; the high voltages can be rapidly turned on and off in ca. 1 ms. A nano-ESI-MS or nano-flow LC/ESI-MS experiment using a Q-TOF coupled with the above system gave mass accuracies within 3 ppm for measurements of ions up to m/z 1000 using subpicomole samples.     

Production of (2R,3S)-3-(4-methoxyphenyl)glycidic acid methyl ester using an emulsion bioreactor containing lipase fromSerratia marcescens

An emulsion bioreactor for production of (2R,3S)-3-(4-methoxyphenyl) glycidic acid methyl ester ([-]MPGM) from a racemic mixture ([±]MPGM) using the lipase fromSerratia marcescens has been proposed. Kinetics of hydrolyzing reaction and purification of (-)MPGM from the reaction mixture were investigated to provide a basis for industrial application of this bioreactor. The hydrolyzing reaction in the bioreactor proceeded at a rate that was first order in substrate concentration. The reaction rate was affected by a stirring speed and the ratio of the aqueous phase containing lipase to the toluene phase containing substrate. Phase separation after the enzymatic reaction was accomplished by addition of surfactant to the reaction mixture, and crystalline (-)MPGM with a chemical purity of 100% and optical purity of 100% enantiomeric excess was obtained in a high yield of 40–43% by concentration of the toluene solution.     

Synthetic study of macquarimicins: highly stereoselective construction of the AB-ring system

The highly stereoselective synthesis of the AB-ring system of macquarimicins, a novel class of microbial metabolites with inhibitory activity for neutral sphingomyelinase, has been achieved. The present synthesis features the highly stereocontrolled construction of the cis-tetrahydroindan structure via the intramolecular Diels-Alder reaction of an (E,Z,E)-1,6,8-nonatriene derived from D-glyceraldehyde acetonide. Reaction: see text.     

Synthesis and characterization of aromatic poly(ether sulfone)s containing pendant sodium sulfonate groups

Poly(ether sulfone)s containing pendant sodium sulfonate groups were prepared by the aromatic nucleophilic substitution reaction of 4,4′-dichlorodiphenylsulfone ( 1 ) and sodium 5,5′-sulfonylbis (2-chlorobenzenesulfonate) ( 2 ) with bisphenols ( 3 ) in the presence of potassium carbonate in N,N-dimethylacetamide. A new monomer 2 containing the sodium sulfonate groups was synthesized by the sulfonation of 1 with fuming sulfuric acid. The polycondensation proceeded smoothly at 170°C and produced the desired poly(ether sulfone)s containing the sodium sulfonate with inherent viscosities up to 1.2 dL/g. The polymers were quite soluble in strong acid, dipolar aprotic solvents, m-cresol, and dichloromethane. The thermogravimetry of the polymers showed excellent thermal stability, indicating that 10% weight losses of the polymers were observed in the range above 460°C in nitrogen atmosphere. Both the glass transition temperatures and hydrophilicity of the polymers increased with increasing their concentrations of sodium sulfonate groups. © 1993 John Wiley & Sons, Inc.     

Total synthesis of (+)-tubelactomicin A. 1. Stereoselective synthesis of the lower-half segment by an intramolecular Diels-Alder approach

[reaction: see text]. Starting from diethyl (R)-malate, synthesis of the lower-half segment of (+)-tubelactomicin A, a 16-membered macrolide antibiotic, has been achieved. The synthesis involved the highly endo- and pi-facial selective intramolecular Diels-Alder reaction achieved using a trisubstituted methacrolein derivative tethering a 10-carbon dienyne unit at the beta-carbon, which in turn was prepared from a known allylated malic acid derivative.     

Stress and Cracks in Gel-Derived Ceramic Coatings and Thick Film Formation

Residual stress was evaluated by measuring the substrate curvature for alkoxide-derived silica and titania films deposited on silica glass substrates. The residual stress was tensile, increasing with increasing heat-treatment temperature. The stress in fired films was affected greatly by water/alkoxide ratio and chelating agents in starting solutions. Secondly, in situ observation was made on cracking of gel films subjected to heat-treatment. Silica and titania gel films deposited on silicon wafers were cracked in the heating-up stage at temperatures of 100°–400°C, depending on the film thickness and heating rate. Larger thickness and lower heating rates were found to lower the cracking onset temperature. Finally, organic polymers with amide groups were demonstrated to increase the uncracking critical thickness. The polymers include polyvinylpyrrolidone and polyvinylacetamide, allowing single layer ceramic coating films over 1 m in thickness to be formed without cracking.     

Biosynthetic studies on the cyclopentane ring formation of allosamizoline, an aminocyclitol component of the chitinase inhibitor allosamidin

Allosamizoline (1) is an aminocyclitol component of allosamidin, a Streptomyces metabolite, and has a cyclopentane ring originated from D-glucosamine. Biosynthesis of the cyclopentane ring was studied by feeding experiments with a variety of deuterium-labeled glucosamine and glucose. In the feeding experiments with [3-(2)H]- and [4-(2)H]-D-glucosamine and [1-(2)H]-D-glucose, deuterium was incorporated into C-3, C-4, and C-1 of 1, respectively. On the other hand, feeding experiments with [5-(2)H]- and [6,6-(2)H(2)]-D-glucosamine showed that deuterium on C-5 and one of the two deuterium atoms on C-6 of glucosamine were lost during the cyclopentane ring formation of 1. In the feeding experiments with (6R)- and (6S)-[6-(2)H(1)]-D-glucose, the (6R)-deuterium of glucose was incorporated into the proS position on C-6 of 1, but the (6S)-deuterium of glucose was not incorporated into 1. These results suggested that an intermediate with a 6-aldehyde group is involved in the biosynthesis of the cyclopentane ring moiety of 1 and overall inversion of stereochemistry of the C-6 methylene group occurred by stereospecific oxidation and reduction on C-6 during the formation of 1. The 6-aldehyde intermediate may play a key role in the biosynthetic step(s) of cyclization to form the cyclopentane ring and/or deoxygenation at C-5.