Methyl-branched poly(hydroxyalkanoate) biosynthesis from 13-methyltetradecanoic acid and mixed isostearic acid isomer substrates.

Pseudomonas resinovorans, a known medium-chain-length (mcl-) poly(hydroxyalkanoate) (PHA) producer, was grown on 13-methyltetradecanoic acid (13-MTDA) and a mixture of isostearic acid (IA) isomers to produce methyl-branched mcl-PHA polymers. Shake-flask experiments revealed polymer productivities (the percent of the cell mass that is polymer) of 31 +/- 1% (n = 3) and 23 +/- 3% (n = 3) when grown in 13-MTDA and IA, respectively. Monomer content was determined by a combination of gas chromatography/mass spectrometry (GC/MS) of the acid hydrolyzed, silylated methyl esters, and nuclear magnetic resonance spectroscopy.

Capabilities of direct sample introduction--comprehensive two-dimensional gas chromatography--time-of-flight mass spectrometry to analyze organic chemicals of interest in fish oils.

Most analytical methods for persistent organic pollutants (POPs) focus on individual groups of targeted analytes. Therefore, analysis of multiple classes of POPs typically entails several sample preparations, fractionations, and injections, whereas other chemicals of possible interest are neglected or lost. To analyze a wider scope of organic contaminants in fish oil, we developed an approach to combine the analysis of targeted and untargeted chemicals using an automated direct sample introduction (DSI) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC x GC/ ToF-MS).

Simultaneous quantitation of multiple classes of organohalogen compounds in fish oils with direct sample introduction comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry.

We successfully optimized an analytical method using gel permeation chromatography followed by direct sample introduction comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry to quantify multiple groups of targeted persistent organic pollutants and halogenated natural products (HNPs) simultaneously in fish oil samples. This new method has a wider analytical scope than the traditional approach to use multiple methods to cover each class of compounds. Our analysis revealed that the relatively more volatile and lighter organic compounds, such as polychlorinated biphenyls (PCBs), organochlorine pesticides, and other smaller organohalogen compounds, were still present in two brands of "PCB-free" cod liver oils, albeit at much lower levels than in an untreated commercial sample.

Catalytic synthesis of biodiesel from high free fatty acid-containing feedstocks.

Recyclable and reusable heterogeneous diarylammonium catalysts are highly effective in catalyzing the esterification of the free fatty acid (FFA) present in greases to methyl esters to reduce the FFA content from 12-40 wt% to 0.5-1 wt%; the resulting ester-glyceride mixture (pretreated grease) could then be readily converted to methyl esters by base-catalyzed transesterification.

Applications of 4,4'-(Me3Si)2-BINAP in transition-metal-catalyzed asymmetric carbon-carbon bond-forming reactions.

[structure: see text] A recently developed BINAP derivative with trimethylsilyl substituents on the 4- and 4'-positions of the binaphthyl skeleton, 2,2'-bis(diphenylphosphino)-4,4'-bis(trimethylsilyl)-1,1'-binaphthyl (tms-BINAP), was used in a variety of transition-metal-catalyzed asymmetric carbon-carbon bond-forming reactions. In pi-allylpalladium-mediated reactions, tms-BINAP gave better enantioselectivity than the unsubstituted BINAP, and the origin of the improved enantioselectivity was gained from an X-ray structural study of [Pd(eta(3)-C(3)H(5))((R)-tms-BINAP)]ClO(4).

Development of 4,4'-substituted-XylBINAP ligands for highly enantioselective hydrogenation of ketones.

[reaction: see text] A family of 4,4'-substituted-xylBINAPs was synthesized in multistep sequences and characterized by NMR spectroscopy and mass spectrometry. Ru(diphosphine)(diamine)Cl(2) complexes based on these 4,4'-substituted-xylBINAPs and chiral diamines (DPEN and DAIPEN) were synthesized by treatment of [(benzene)RuCl(2)](2) with 4,4'-substituted-xylBINAP followed by chiral diamine, and characterized by (1)H and (31)P NMR spectroscopy and mass spectrometry. These Ru complexes were used for asymmetric hydrogenation of aromatic ketones in a highly enantioselective manner with complete conversion.

4,4'-Disubstituted BINAPs for highly enantioselective Ru-catalyzed asymmetric hydrogenation of ketones.

A family of tunable precatalysts Ru(4,4'-BINAP)(chiral diamine)Cl2 was synthesized and used for highly enantioselective hydrogenation of aromatic ketones. This result differs from previous chiral diphosphines that rely on the bis(xylyl)phosphino groups to control enantioselectivity. An X-ray structural study reveals that the bulky substituents on the 4,4'-positions of BINAP can effectively create a suitable chiral pocket in the transition state and thus provide a new mechanism for the enantiocontrol in such a remarkable asymmetric catalytic process.

Luminescent homochiral silver(I) lamellar coordination networks built from helical chains.

The reactions of 2,2'-dimethoxy-1,1'-binaphthyl-3,3'-bis(4-vinylpyridine)(L) with AgNO3 or AgClO4 at 70 degrees C gave rise to two novel luminescent homochiral lamellar coordination polymers, AgL2X (X = NO3- for 1 or ClO4- for 2), which are built from linking helical chains by Ag(I) atoms as hinges.

Chiral porous hybrid solids for practical heterogeneous asymmetric hydrogenation of aromatic ketones.

Chiral porous zirconium phosphonates containing Ru-BINAP-DPEN moieties were synthesized via a molecular building-block approach, and characterized by a variety of techniques including TGA, adsorption isotherms, XRD, SEM, IR, and microanalysis. These hybrid solids were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with remarkably high ee values of up to 99.2%.

Highly enantioselective catalytic asymmetric hydrogenation of beta-keto esters in room temperature ionic liquids.

Polar phosphonic acid-derived Ru-BINAP systems were used to catalyze asymmetric hydrogenation of beta-keto esters in room temperature ionic liquids (RTILs) with complete conversions and ee values higher than those obtained from homogeneous reactions in MeOH (up to 99.3%), and were recycled by simple extraction and used for four times without the loss of activity and enantioselectivity.

A homochiral triple helix constructed from an axially chiral bipyridine.

A homochiral triple helix was self-assembled from an axially chiral bipyridine and a linear metal-connecting point, which further assembles into a 2D network via infinite pi...

Homochiral 3D open frameworks assembled from 1- and 2-D coordination polymers.

Homochiral 3D open frameworks have been assembled from 1- and 2-D coordination structures via hydrogen bonding and are stable towards the removal of included guest molecules.

Hierarchical assembly of homochiral porous solids using coordination and hydrogen bonds.

A family of homochiral metal carboxylate coordination polymers have been synthesized by treating 2,2'-dihydroxy-1,1'-binaphthalene-6,6'-dicarboxylic acid (H(2)BDA) with metal salts at elevated temperatures. BDA ligands link adjacent metal centers to form 1D coordination polymeric chains using the carboxylate functionality, while the hydroxyl groups of BDA ligands form H-bonds with carboxylate oxygen atoms to link 1D coordination polymeric chains into open frameworks of higher dimensionality. We also present evidence for the important role played by H-bonds in the stabilization of open framework structures which allows for the hierarchical assembly of chiral porous solids.

Chiral crown ether pillared lamellar lanthanide phosphonates.

A new chiral bridging ligand, 2,2'-pentaethylene glycol-1,1'-binaphthyl-6,6'-bis(phosphonic acid), was synthesized in 40.7% overall yield in five steps and used to generate single crystals of the first porous lanthanide phosphonates with chiral crown ether pillars. Single-crystal and powder X-ray crystallography established that these chiral crown ether decorated lamellar solids retain their framework structures after the removal of their included guest molecules and serve as structural models for porous solids that are exploitable for bulk chiral separations.

Self-assembly of nanoscale, porous T-symmetric molecular adamantanoids.

Treatments of lanthanide nitrate or perchlorate and C2-symmetric 2,2'-hydroxy-1,1'-binaphthalene-6,6'-dicarboxylic acid (6,6'-H2BDA) led to diastereoselective self-assembly of nanoscale, porous molecular adamantanoids [Ln4(BDA)6(H2O)12]*12DMF (Ln = Gd, La, 1a,b). These adamantanoid clusters possess perfect T symmetry as a result of the C2-symmetric nature of BDA bridging ligands and C3-symmetric nature of lanthanide ions. Face-to-face intercluster hydrogen bonds formed between 2,2'-dihydroxyl groups of BDA ligands and carboxylate oxygen atoms direct the assembly of 3D polycages based on chiral molecular adamantanoid building blocks which possess two different types of open channels.

Homochiral 3D lanthanide coordination networks with an unprecedented 4(9)6(6) topology.

Homochiral 3D metal-organic open frameworks based on enantiopure atropisomeric dicarboxylic acid bridging ligands and dilanthanide secondary building units exhibit an unprecedented 4(9)6(6) topology, and possess ethoxy-protected BINOL functionalities that are pointing toward the open channels.

New rigid angular dicarboxylic acid for the construction of nanoscopic supramolecules: from a molecular rectangle to a 1-D coordination polymer.

A new rigid angular bridging ligand, 7-oxa-dibenzofluorene-3,11-dicarboxylic acid (H(2)L), was synthesized by cyanation of known rac-6,6'-dibromo-1,1'-bi-2-naphthol followed by ring closure and hydrolysis with concentrated sulfuric acid and used for the self-assembly of nanoscopic molecular rectangle [Cu(4)(L)(4)(Py)(8)].2DMF.10H(2)O, 1, and 1-D coordination polymer [Co(2)(L)(2)(Py)(4)].