ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA New Bifunctional Asymmetric Catalysis: An Efficient Catalytic Cyanosilylation of AldehydesYoshitaka Hamashima, Daisuke Sawada, Motomu Kanai, and Masakatsu ShibasakiView Author Information Graduate School Pharmaceutical Sciences The University Tokyo Hongo, Bunkyo-ku, 113-0033, Japan Cite this: J. Am. Chem. Soc. 1999, 121, 11, 2641–2642Publication Date (Web):March 4, 1999Publication History Received11 November 1998Published online4 March...

Obtaining a better understanding of the complex mechanisms occurring during lignocellulosic deconstruction is critical to continued growth renewable biofuel production. A key step in bioethanol production thermochemical pretreatment reduce plant cell wall recalcitrance for downstream processes. Previous studies dilute acid (DAP) have shown significant changes cellulose ultrastructure that occur pretreatment, but there still substantial knowledge gap with respect influence lignin on these...

Abstract Determining the shape of plant cellulose microfibrils is critical for understanding cell wall molecular architecture and conversion into biofuels. Only recently has it been determined that these are composed 18 chains rather than 36 polymers arranged in a diamond-shaped pattern. This study uses density functional theory calculations to model three possible habits 18-chain microfibril compares calculated energies, structures, 13 C NMR chemical shifts WAXS diffractograms each evaluate...

Cellulose nanopaper is a strong lightweight material made from renewable resources with wide range of potential applications, membranes to electronic displays. Most studies on target high mechanical strength, which compromises ductility and toughness. Herein, we demonstrate the fabrication highly ductile tough cellulose via fibrillation hemicellulose-rich wood fibers dispersion obtained nanofibrils (CNFs) in an ionic liquid (IL)–water mixture. This treatment allows hemicellulose swelling,...

Abstract The production of sustainable and high-performance fabrics requires high mechanical strength the individual (staple) fibers. Although Ioncell fibers already exhibit higher fiber than commercial man-made cellulose or cotton fibers, we further aimed to increase both toughness gradually approach synthetic in these properties. Decisive factors for achievable properties were pulp purity, concentration spinning solution length-to-diameter (L/D) ratio cylindrical part spinneret. absence...

Abstract Naturally occurring plant cellulose, our most abundant renewable resource, consists of fibers long polymer chains that are tightly packed in parallel arrays either two crystal phases collectively referred to as cellulose I. During mercerization, a process involves treatment with sodium hydroxide, goes through conversion another form called II, within which every other chain has remarkably changed direction. We designed neutron diffraction experiment deuterium labelling order...

An enantioselective total synthesis of epothilones A (1) and B (2) using multifunctional asymmetric catalysis such as a cyanosilylation an aldehyde, aldol reaction unmodified ketone with protonation in the conjugate addition thiol to α,β-unsaturated thioester has been achieved. We divided 1 2 into fragment A, B, C. catalytic fragments was accomplished key step. enantiocontrolled C achieved two ways. One is use direct aldehyde step, other utilizes Suzuki cross-coupling followed by Yamaguchi...

Quorum sensing (QS) systems have been discovered in a wide variety of bacteria, and mediate both intra- interspecies communication. The AI-2-based QS system represents the most studied these proposed has shown to regulate diverse functions such as bioluminescence, expression virulence factors, biofilm formation. As such, development modulatory compounds, agonists antagonists, is great interest for study unknown potential treatment bacterial infections. fimbrolide class natural products...

We report a macroscopically anisotropic hydrogel developed by the facile dialysis of synthetic semirigid polyanion in aqueous solution multivalent cations. By uniaxial diffusion Ca2+ into two ends thin rectangular reaction cell containing poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT) solution, centimeter-scale hydrogels with PBDT molecules and their self-assembled fibrous bundles align perpendicular to direction are obtained. The gel shows higher elastic modulus tensile...

A robust, macroscopically anisotropic double-network (A-DN) hydrogel has been developed by combining the first anisotropic, physically cross-linked network of semirigid poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT) and second chemically flexible polyacrylamide (PAAm) through technology. Owing to cooperative orientation self-assembled bundle structure PBDTs, A-DN gel shows a very sensitive strong birefringence change upon deformation, which is always dominated PBDT for wide...

The complete crystal structure (including hydrogen) of dihydrate β-chitin, a homopolymer N-acetylglucosamine hydrate, was determined using high-resolution X-ray and neutron fiber diffraction data collected from bathophilous tubeworm Lamellibrachia satsuma. Two water molecules per residue are clearly localized in the these participate most hydrogen bonds. conformation labile acetamide groups hydroxymethyl similar to those found anhydrous but more relaxed. Unexpectedly, intrachain O3-H…O5 bond...

Abstract A novel, small‐volume vertically arranged spin bath was successfully developed for an air gap lyocell‐type spinning process. maximum regeneration length with a minimum free volume characterizes the concept of new bath. Using ionic liquid (IL) 1,5‐diazabicyclo[4.3.0]non‐5‐enium acetate [DBNH][OAc], showed very good performances IL‐cellulose dopes at high draw ratios and duration single filament experiments. this device, it possible to get step further in optimization Ioncell® process...

Abstract Lyocell fibers have received increased attention during the recent years. This is due to their high potential satisfy rising market demand for cellulose-based textiles in a sustainable way. Typically, this technology adopts dry-jet wet spinning process, which offers regenerated cellulose of excellent mechanical properties. Compared widely exploited viscose lyocell fosters an eco-friendly process employing green direct solvents that can be fully recovered with low environmental...

A catalytic version has now been developed for the enantioselective total synthesis of epothilone (1). The key is use multifunctional asymmetric catalyses a direct aldol reaction and cyanosilylation. This successful approach demonstrated usefulness these reactions complex molecules.

ADVERTISEMENT RETURN TO ISSUEPerspectiveNEXTMedicinal Chemistry as a Conduit for the Modulation of Quorum SensingColin A. Lowery†, Nicholas T. Salzameda†, Daisuke Sawada†, Gunnar F. Kaufmann†, and Kim D. Janda*†‡View Author Information† Department Immunology Microbial Science, The Skaggs Institute Chemical Biology, Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037‡ Worm Medicine (WIRM), 92037*To whom correspondence should be addressed. Phone: (858) 784-2516....

ABSTRACT We determined the crystal structure of anhydrous chitosan at atomic resolution, using X‐ray fiber diffraction data extending to 1.17 Å resolution. The unit cell [a = 8.129(7) Å, b 8.347(6) c 10.311(7) space group P2 1 2 ] contains two chains having one glucosamine residue in asymmetric with primary hydroxyl gt conformation, that could be directly located Fourier omit map. molecular arrangement is very similar corner cellulose II implying intermolecular hydrogen bonding between O6...

A low carbon yield is a major limitation for the use of cellulose-based filaments as fiber precursors. The present study aims to investigate an abundant biopolymer chitosan natural charring agent particularly on enhancing cellulose-derived fiber. ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH]OAc) was used direct dissolution cellulose and spin cellulose–chitosan composite fibers through dry-jet wet spinning process (Ioncell). homogenous distribution tight packing revealed by...

A new type of polysaccharide (hemicellulose) nanocrystal, bearing the shape an anisotropic nanoflake, emerged from a dimethyl sulfoxide (DMSO) dispersion wood-based xylan through heat-induced crystallization. The dimensions these nanocrystals were controlled by crystallization conditions. Sharp signals in solid-state NMR indicated well-ordered crystal structure. unit cell is constituted two asymmetric xylose residues, and DMSO molecules resided host–guest arrangement with more than one local...

The hydrogen bonding arrangement in anhydrous β-chitin, a homopolymer of N-acetylglucosamine, was directly determined by neutron fiber diffraction. Data were collected from sample prepared the bathophilous tubeworm Lamellibrachia satsuma which all labile atoms had been replaced deuterium. Initial positions deuterium on hydroxyl and acetamide groups located Fourier maps synthesized using phases calculated X-ray structure amplitudes measured data. bond refined is general agreement with...

In plant cell walls and cellulose-containing composites, nanocrystalline cellulose interacts with water molecules or matrix polymers through hydrogen bonding of the hydroxyl groups at surface. These interactions play key roles in assembly mechanical properties composites; however, they could not be studied properly due to spectroscopic difficulty selectively detecting surface domains. This study employed sum frequency scattering principle distinguish inside crystalline nanodomain those...

Tension wood is a type of reaction in response to bending or leaning stem as corrective growth process. formed by both natural and man-made processes. Most attractively, tension contains higher glucan content undergoes enzymatic conversion fermentable sugars. Here, we have employed structural techniques, small-angle neutron scattering (SANS) wide-angle X-ray diffraction (WAXD) elucidate morphological aspects conducive sugar yields. Small-angle data exhibited tri-modal distribution the fibril...