Polyaromatic amines. Part 3: Synthesis of poly(diarylamino)styrenes and related compounds

The title compounds were synthesised and characterised as part of a study into new aromatic amines for charge transporting materials. Compounds 12-16, 20-24 and 27-34 are alkene linked triarylamines, compounds 35-36 are hydrazone derivatives and compounds 38-41 are pyrrole substituted triarylamines. Each compound was characterised by cyclic voltammetry.     

Functionalized nanoparticles for liquid atmospheric pressure matrix-assisted laser desorption/ionization peptide analysis

Nanoparticles for the extraction of peptides and subsequent analysis using atmospheric pressure matrix-assisted laser desorption/ionization (APMALDI) have been evaluated. The atmospheric pressure source allows for particles to be directly introduced in the liquid matrix, minimizing sample loss and analysis time. Described in this work are two sample preparation procedures for liquid APMALDI analysis: a C18 functionalized silica nanoparticle for hydrophobic extractions, and an aptamer functionalized magnetite core nanoparticle for rapid, affinity extractions. The C18 particles provide a non-selective support for rapid profiling applications, while the aptamer particles are directed towards reducing the complexity in biological samples. The aptamer functionalized particles provide a more selective analyte-nanoparticle interaction whereby the tertiary structure of the analyte becomes more critical to the extraction. In both cases, the liquid APMALDI matrix provides a support for ionization, and acts as the releasing agent for the analyte-particle interaction. Additionally, analyte enrichment was possible due to the large surface-to-volume ratio of the particles. The experiments conducted with functionalized nanoparticles, in an atmospheric pressure liquid matrix, present a basis for further methodologies and utilities of silica nanoparticles to be developed.     

On the semimartingale representation of reflecting Brownian motion in a cusp

Summary LetC be the symmetric cusp {(x, y)²:–x yx ,x0} where >1. In this paper we decide whether or not reflecting Brownian motion inC has a semimartingale representation. Here the reflecting Brownian motion has directions of reflection that make constant angles with the unit inward normals to the boundary. Our results carry through for a wide class of asymmetric cusps too.     

Light olefin production from CO/H2 over silica supported Fe/Mn/K catalysts derived from a bimetallic carbonyl anion, [Fe2Mn(CO)12]?

Fe/Mn/K catalysts derived from support of the anionic carbonyl, [Fe₂Mn(CO)₁₂]^– on silica were compared with catalysts prepared by aqueous impregnation methods, and found to be more selective for production of C₂–C₄ olefins. Addition of K had little effect, whereas variations in reaction conditions altered selectivity owing to secondary reactions of the alkene products.

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Fe/Mn/K, , [Fe₂Mn(CO)₁₂]^–, , , , C₂–C₄. , , .

     

Polyurethane elastomers with hydrolytic and thermooxidative stability. II. Polyurethanes with n-alkylated polyurethane soft blocks

Block copolyurethanes with N-alkylated polyurethanes as nonself-associating soft segments are prepared. The polymers compare well in hydrolytic stability with block copoly(N-alkylamide urethane)s prepared in an earlier study but have better dimensional stability on exposure to moist heat. They show comparable hydrolytic stability and better oxidative stability than a poly(ether urethane) from the earlier study. The effect of different alkyl substituents on tensile properties and thermostability is studied. The tensile properties are also examined as a function of soft-segment molecular weight at constant weight-percent of hard-block. It is shown that yield stress and ultimate stress increase and elongations decrease as the soft-block M?_n increases. DSC measurements do not generally show well defined endotherms with few exceptions but dynamic mechanical testing of some samples does show transitions between 14 and 23°C.     

Polyketide double bond biosynthesis. Mechanistic analysis of the dehydratase-containing module 2 of the picromycin/methymycin polyketide synthase

Picromycin/methymycin synthase (PICS) is a modular polyketide synthase (PKS) that is responsible for the biosynthesis of both 10-deoxymethynolide (1) and narbonolide (2), the parent 12- and 14-membered aglycone precursors of the macrolide antibiotics methymycin and picromycin, respectively. PICS module 2 is a dehydratase (DH)-containing module that catalyzes the formation of the unsaturated triketide intermediate using malonyl-CoA as the chain extension substrate. Recombinant PICS module 2+TE, with the PICS thioesterase domain appended to the C-terminus to allow release of polyketide products, was expressed in Escherichia coli. Purified PICS module 2+TE converted malonyl-CoA and 4, the N-acetylcysteamine thioester of (2S,3R)-2-methyl-3-hydroxypentanoic acid, to a 1:2 mixture of the triketide acid (4S,5R)-4-methyl-5-hydroxy-2-heptenoic acid (5) and (3S,4S,5R)-3,5-dihydroxy-4-methyl-n-heptanoic acid-delta-lactone (10) with a combined kcat of 0.6 min(-1). The triketide lactone 10 is formed by thioesterase-catalyzed cyclization of the corresponding d-3-hydroxyacyl-SACP intermediate, a reaction which competes with dehydration catalyzed by the dehydratase domain. PICS module 2+TE showed a strong preference for the syn-diketide-SNAC 4, with a 20-fold greater kcat/K(m) than the anti-(2S,3S)-diketide-SNAC 14, and a 40-fold advantage over the syn-(2R,3S)-diketide-SNAC 13. PICS module 2(DH(0))+TE, with an inactivated DH domain, produced exclusively 10, while three PICS module 2(KR(0))+TE mutants, with inactivated KR domains, produced exclusively or predominantly the unreduced triketide ketolactone, (4S,5R)-3-oxo-4-methyl-5-hydroxy-n-heptanoic acid-delta-lactone (7). These studies establish for the first time the structure and stereochemistry of the intermediates of a polyketide chain elongation cycle catalyzed by a DH-containing module, while confirming the importance of key active site residues in both KR and DH domains.     

Preparative access to medicinal chemistry related chiral alcohols using carbonyl reductase technology

Libraries of highly enantioenriched secondary alcohols in both enantiomeric forms were synthesised by enzymatic reduction of their parent ketones using selectAZyme? carbonyl reductase (CRED) technology. Commercially available CREDs were able to reduce a range of substrate classes efficiently and with very high enantioselectivity. Matching substrate classes to small subsets of CREDs enabled the fast development of preparative bioreductions and the rapid generation of 100–1500 mg samples of chiral alcohols in typically >95% ee and the majority in ?99.0% ee. The conditions for small scale synthesis were then scaled up to 0.5 kg to deliver one of the chiral alcohols, (S)-1-(4-bromophenyl)-2-chloroethanol, in 99.8% ee and 91% isolated yield.     

Synthesis and characterization of eumelanin‐inspired poly(indoylenearylenevinylene)s and poly(indoylenearyleneethynylene)s

Four novel conjugated polymers containing the eumelanin‐inspired indole core have been successfully synthesized using common cross coupling reactions. These polymers differed by the arylene and the carbon–carbon bond linkage. Optoelectronic experiments of these polymers suggest that the ethynylene linkage contributed to the red‐shifted absorption spectra and blue‐shifted emission spectra when compared to the vinylene linkage polymers. Furthermore, the optical bandgaps of the poly(indoylenearyleneethynylene)s (PIAEs) were smaller compared to the poly(indoylenearylenevinylene)s (PIAVs). Surprisingly, the HOMOs of these polymers were less affected by the nature of the carbon–carbon linkage. However, the LUMOs of the PIAEs were lower in comparison to the PIAVs. These eumelanin‐inspired PIAEs and PIAVs are good fluorophores with fluorescence quantum yields ranging from 0.12 to 0.67 and have good thermal stability for applications such as in organic light‐emitting diodes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 457–463     

Synthesis of cananodine by intramolecular epoxide opening

Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared.