Release of intracellular enzymes increases the total extracellular activities of carbohydrate-processing enzymes in marine environment.

Microbial extracellular enzymatic activities (EEAs) produced by microbes to degrade biopolymers are the 'gatekeeper' of carbon cycle in the marine ecosystem. It is usually assumed that these extracellular enzymes are actively secreted by microbes. However, biopolymer-degrading enzymes also exist in the intracellular space.

Identification and Characterization of Three Chitinases with Potential in Direct Conversion of Crystalline Chitin into ,'-diacetylchitobiose.

Chitooligosaccharides (COSs) have been widely used in agriculture, medicine, cosmetics, and foods, which are commonly prepared from chitin with chitinases. So far, while most COSs are prepared from colloidal chitin, chitinases used in preparing COSs directly from natural crystalline chitin are less reported. Here, we characterize three chitinases, which were identified from the marine bacterium DSM 14401, with an ability to degrade crystalline chitin into (GlcNAc) ('-diacetylchitobiose).

Exploiting Pincer Ligands to Perturb the Geometry at Boron.

Boranes are ubiquitous in synthesis and materials but advancements in their development have been primarily restricted to the geometric energetic minima, trigonal planar complexes. This report discloses a class of boranes with expanded bond angles achieved by taking advantage of the structural rigidity of tridentate pincer ligands. The bonding of these novel boranes is investigated by X-ray crystallography and computationally.

Ring expansion reactions of anti-aromatic boroles: a promising synthetic avenue to unsaturated boracycles.

Conjugated boron heterocycles have emerged as attractive synthetic targets due to their potential in medicinal chemistry and as electronic materials. However, the development of unsaturated boracycles has been hampered by difficulties in their preparation. Recently, a new synthetic avenue to access these species has been developed that takes advantage of the high reactivity of boroles.

Probing the reactivity of pentaphenylborole with N-H, O-H, P-H, and S-H bonds.

The reactions of molecules containing E-H functionalities (E = Group 15 or 16 element) and pentaphenylborole were investigated revealing diverse outcomes. For aniline and water, protodeborylation ring opening reactions occurred via the N-H or O-H bonds. Pentaphenylborole reacted with water in a 1 : 1 or 2 : 1 ratio to yield the corresponding boroxane and diboroxane, respectively, whereas aniline reacted strictly in a 1 : 1 ratio.

Peculiar Reactivity of Isothiocyanates with Pentaphenylborole.

The reactions of isothiocyanates with the antiaromatic pentaphenylborole were investigated, revealing significantly different outcomes than the analogous reactions with isocyanates. The 1:1 stoichiometric reaction products isolated include a seven-membered BNC5 heterocycle and a fused bicyclic 4/5-ring system. Studies suggest that the seven-membered ring undergoes an intramolecular [2 + 2] electrocyclic ring closure to produce the bicyclic system.

Reactions of imines, nitriles, and isocyanides with pentaphenylborole: coordination, ring expansion, C-H bond activation, and hydrogen migration reactions.

The reactions of pentaphenylborole with imines, isocyanides, and acetonitrile were investigated experimentally and theoretically. On the basis of literature precedent, we envisioned that the dipolar substrates would undergo facile ring expansion reactions to yield new BNC5 heterocycles. For acetonitrile and one particular imine, this ring expansion process was observed.

Ring expansion reactions of pentaphenylborole with dipolar molecules as a route to seven-membered boron heterocycles.

Reactions of pentaphenylborole with isocyanates, benzophenone, and benzaldehyde produced new seven-membered heterocycles in high yields. For 1-adamantyl isocyanate, a BNC5 heterocycle was obtained from the insertion of the C-N moiety into the five-membered borole, whereas for 4-methoxyphenyl isocyanate, a BOC5 heterocycle was generated from the insertion of the C-O unit. These reactions are believed to occur via a mechanism wherein coordination of the nucleophile to the borole (1-adamantyl, N-coordination or O-coordination for 4-methoxyphenyl) is followed by ring expansion to afford the observed seven-membered heterocycles.

Enantioselective hydrogenation of α,β-disubstituted nitroalkenes.

The first highly chemo- and enantioselective hydrogenation of α,β-disubstituted nitroalkenes was accomplished with rhodium/JosiPhos-J2 as a catalyst, with the yield and enantioselectivity of up to 95% and 94%, respectively. The α-chiral nitroalkanes will provide an entry to valuable chiral amphetamines which are otherwise not so easily accessed.

Rhodium-catalyzed asymmetric hydrogenation of unprotected NH imines assisted by a thiourea.

Asymmetric hydrogenation of unprotected NH imines catalyzed by rhodium/bis(phosphine)-thiourea provided chiral amines with up to 97% yield and 95% ee. (1)H NMR studies, coupled with control experiments, implied that catalytic chloride-bound intermediates were involved in the mechanism through a dual hydrogen-bonding interaction. Deuteration experiments proved that the hydrogenation proceeded through a pathway consistent with an imine.

Direct catalytic asymmetric reductive amination of simple aromatic ketones.

A green method for chiral amine synthesis, the direct catalytic asymmetric reductive amination, was developed. Phenylhydrazide is an ideal nitrogen source for reductive amination. Molecular sieves play dual roles in this reaction.

A novel chiral bisphosphine-thiourea ligand for asymmetric hydrogenation of β,β-disubstituted nitroalkenes.

A novel chiral bisphosphine-thiourea ligand was developed and applied in the highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes (up to 99% yield and 99% ee). With low catalytic loading (0.25 mol %), 98% ee and 98% conversion were obtained.

Rhodium-catalyzed highly regioselective hydroaminomethylation of styrenes with tetraphosphorus ligands.

The highly linear-selective hydroaminomethylation of styrenes is very challenging. Herein, an efficient, highly chemoselective, and linear-selective hydroaminomethylation (l/b up to >99:1) of styrenes using Rh(nbd)2SbF6 with a pyrrole-based 3,3',5,5'-substituted tetraphosphorus ligand is documented. This is in sharp contrast to other available processes leading to branched amines and provides a novel atom economic approach to 3-arylpropylamines.

Cascade synthesis of fenpiprane and related pharmaceuticals via rhodium-catalyzed hydroaminomethylation.

A novel rhodium catalytic system with Naphos as ligand was developed for an efficient hydroaminomethylation of 1,1-diphenylethene under relatively mild conditions. This will allow for an atom-economic and environmentally benign synthesis of fenpiprane and related pharmaceuticals.

Rhodium-catalyzed enantioselective hydrogenation of oxime acetates.

Rh-catalyzed enantioselective hydrogenation of oxime acetates was first reported, which afforded a new approach for chiral amine synthesis.

Highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes.

Building the building blocks: A highly enantioselective hydrogenation of β-aryl-β-alkyl disubstituted nitroalkenes 1 has been developed. This method results in enantiomerically pure nitroalkanes 2, which are versatile precursors for chemical synthesis.

Highly regioselective isomerization-hydroaminomethylation of internal olefins catalyzed by Rh complex with Tetrabi-type phosphorus ligands.

A highly regioselective isomerization-hydroaminomethylation of internal olefins has been developed. A 95.3% amine selectivity and 36.

Highly regioselective hydroaminomethylation of terminal olefins to linear amines using Rh complexes with a Tetrabi phosphorus ligand.

A highly regioselective hydroaminomethylation of terminal olefins catalyzed by Rh complexes with 2, 2', 6, 6'-tetrakis ((diphenylphosphino)methyl)-1, 1'-biphenyl (Tetrabi) ligand has been developed. Up to 99 % amine selectivity, 168 linear/branched amine product ratio (n/i), and 97.4 % linear amine yield has been obtained at a substrate/rhodium precursor ratio (S/Rh) of 1000 with this methodology.

Enantioselective synthesis of optically pure β-amino ketones and γ-aryl amines by Rh-catalyzed asymmetric hydrogenation.

A series of optically pure β-amino ketones have been synthesized in high enantioselectivities (ee > 99%) by Rh-DuanPhos-catalyzed asymmetric hydrogenation of readily prepared β-keto enamides. Further reduction of these β-amino ketones with hydrogen and Pd/C leads to the formation of a variety of protected enantiomerically pure γ-aryl amines (ee > 99%), which are key building blocks in many bioactive molecules.

Design and synthesis of a novel three-hindered quadrant bisphosphine ligand and its application in asymmetric hydrogenation.

A novel three hindered quadrant bisphosphine ligand has been synthesized. The ligand shows excellent enantioselectivities and reactivities for rhodium-catalyzed hydrogenations of various functionalized olefins.

Three new heterothiometallic cluster polymers with fascinating topologies.

Three new heterothiometallic cluster polymers with fascinating topologies have been synthesized by the self-assembly of preformed heterothiometallic cluster monomers and appropriate ligands. Reaction of the monomeric cubic-shaped cluster [Et(4)N](3)[MoOS(3)Cu(3)I(4)] with the D(2h) symmetry rigid bidentate 4,4'-bipy (4,4'-bipyridine) gave a two-dimensional (2D) layer compound [Mo(2)O(2)S(6)Cu(6)I(2)(4,4'-bipy)(3)(H(2)O)](n) (1); the assembly of pentanuclear cluster monomer [Et(4)N](4)[WS(4)Cu(4)I(6)] with C(s)-symmetrical bpe (1,2-bis(4-pyridyl)ethane) afforded a 2D layer compound [WS(4)Cu(4)I(2)(bpe)(3)(H(2)O)](n) (2), and the assembly of heptanuclear cluster monomer [Et(4)N](4)[WS(4)Cu(6)I(8)] with D(3h) symmetry trigonal planar ligand timtz (2, 4, 6-tri(1H-imidazol-1-yl)-1, 3, 5-triazine) afforded a three-dimensional (3D) compound [WS(4)Cu(6)I(4)(timtz)(8/3)(H(2)O)(12)](n) (3). X-ray crystallographic analysis reveals that 1 crystallizes in trigonal space group R3c with 2D 3(6)-hxl net which is the first heterothiometallic superamolecular structure based on a twin cubic-shaped cluster monomer and also the first example of 4,4'-bipy-connected compound of this net.

Synthesis of enamides via Rh/C-catalyzed direct hydroacylation of ketoximes.

Enamides were efficiently prepared via a novel Rh/C-catalyzed direct hydroacylation of ketoximes. Up to 88% isolated yield of enamides were obtained with this method. Subsequent asymmetric hydrogenation of the enamides with Rh/DuanPhos complex gave the corresponding chiral amine in excellent enantioselectivities (up to 99.

Porous nonlinear-optical material based on a twin-nest-shaped heterothiometallic cluster: {[NH(4)][W(2)O(2)S(6)Cu(6)I(3)(4,4'-bipy)(4)].5H(2)O}n.

A novel 3D porous coordination complex based on a twin-nest-shaped heterothiometallic cluster has been synthesized and characterized. The complex shows an unprecedented structure type and interesting nonlinear-optical properties. Its gas sorption property was studied and shown to be comparable to that of previously reported metal-organic frameworks.