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. Results showed that the mcl-PHA polymer derived from 13-MTDA was primarily composed of 3-hydroxy-7-methyloctanoic acid and 3-hydroxy-9-methyldecanoic acid (67 and 16 mol% by GC/MS, respectively). In contrast, the mcl-polymers synthesized from the IA isomeric mixture were more complex, containing both even and odd chain-length monomers as well as varying distributions of methyl-branched derivatives. The PHA distributions among the C8, C10, C12, and C14 carbon chain-length monomers included three isomers of C8, five isomers of C10, seven isomers of C12, and nine isomers of C14 each containing one linear-chain derivative and n-6 methyl-branched derivatives where n equals the total number of carbon atoms in each monomer unit (C8-C14).

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). DSI-GC x GC/ToF-MS is a powerful tool that attains high quality separations to achieve high selectivity while still providing a wide analytical scope with minimal sample preparation, especially in conjunction with DSr's high tolerance to dirty extracts. Gel permeation chromatography (GPC) was used for initial separation of lipids from POPs and other GC-amenable organic compounds from dietary cod liver oil. For comparison purposes, additional cleanup of the GPC extracts was done by silica adsorption and acidification, which helped provide clues in the identification of untargeted compounds, but in routine analysis, only GPC is needed for this analytical approach. The approach allowed simultaneous identification of known-POPs in the fish liver oils, and further permitted presumptive identifications of multiple groups of halogenated natural products (HNPs) and other organic chemicals of interest through comparisons of the mass spectra from analyses with those from mass spectral libraries and/or reports in the literature (approximately 60 PCB congeners and 76 compounds in total). Subsequent confirmations were made by reanalysis and comparison of chromatographic retention times and mass spectra with contemporaneously analyzed reference standards. Otherwise, ion fragmentation patterns of unknown compounds were assessed for tentative identifications. Some of the HNPs in the fish oils were detected and identified for the first time. Our study demonstrates that the wide monitoring scope provided by the DSI-GC x GC/ToF-MS method after GPC provides many logistical and performance advantages over the conventional use of several different methods designed for individual classes of targeted analytes after extensive sample preparation.

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. Moreover, the less volatile organic compounds, such as polybrominated diphenyl ethers and brominated HNPs, were detected at similar levels in all three cod liver oils. This suggests that the commercial molecular distillation treatment used for removal of organic/inorganic toxic contaminants is only effective for the lighter organic contaminants.

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. With 0.1% catalyst loading, complete conversion and enantioselectivity greater than 99% were obtained for most of the aromatic ketones examined. These Ru catalysts thus gave the highest ee for asymmetric hydrogenation of aromatic ketones among all of the catalysts reported in the literature. A single-crystal X-ray diffraction study of Ru[(R)-L(4)()][(R,R)-DPEN]Cl(2) indicated that the 4-methyl group of the naphthyl ring and the methyl groups of the two xylyl moieties form a fence on the opposite side of the DPEN ligand of the Ru center. These three methyl groups will have significant repulsive interactions with the bulky aryl ring of the hydrogen-bonded aromatic ketone in the disfavored transition state. These results support our hypothesis of combining dual modes of enantiocontrol (i.e., the substituents on 4,4'-positions of the binaphthyl framework and the methyl groups on the bis(xylyl)phosphino moieties) to achieve higher stereoselectivity in the hydrogenation of aromatic ketones.

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%. These solid catalysts can also be easily recycled and reused for eight times without the loss of activity and enantioselectivity. Ready tunability of such a molecular building-block approach will allow the optimization of these hybrid materials and promise to lead to other practically useful heterogeneous asymmetric catalysts.

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...pi stacking interactions and acts as a host for the inclusion of guest molecules.

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.

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.

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.

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)].2DMF.2H(2)O, 2. Both 1 and 2 contain open channels occupied by DMF and water guest molecules. Crystal data for 1:[?] triclinic, space group P(-)1, a = 8.869(2) A, b = 16.437(3) A, c = 21.586(4) A, alpha = 78.18(3), beta = 79.19(3), gamma = 83.66(3), U = 3017.0(11) A(3), and Z = 1. Crystal data for 2: triclinic, space group P(-)1, a = 8.254(2) A, b = 12.154(2) A, c = 15.348(3) A, alpha = 95.34(3), beta = 93.38(3), gamma = 94.37(3), U = 1525.1(5) A(3), and Z = 1.