1075-49-6Relevant articles and documents
Structural insights into the role of the acid-alcohol pair of residues required for dioxygen activation in cytochrome P450 enzymes
Coleman, Tom,Stok, Jeanette E.,Podgorski, Matthew N.,Bruning, John B.,De Voss, James J.,Bell, Stephen G.
, p. 583 - 596 (2020)
The cytochrome P450 heme monooxygenases commonly use an acid-alcohol pair of residues, within the I-helix, to activate iron-bound dioxygen. This work aims to clarify conflicting reports on the importance of the alcohol functionality in this process. Mutants of the P450, CYP199A4 (CYP199A4D251N and CYP199A4T252A), were prepared, characterised and their crystal structures were solved. The acid residue of CYP199A4 is not part of a salt bridge network, a key feature of paradigmatic model system P450cam. Instead, there is a direct proton delivery network, via a chain of water molecules, extending to the surface. Nevertheless, CYP199A4D251N dramatically reduced the activity of the enzyme consistent with a role in proton delivery. CYP199A4T252A decreased the coupling efficiency of the enzyme with a concomitant increase in the hydrogen peroxide uncoupling pathway. However, the effect of this mutation was much less pronounced than reported with P450cam. Its crystal structures revealed fewer changes at the I-helix, compared to the P450cam system. The structural changes observed within the I-helix of P450cam during oxygen activation do not seem to be required in this P450. These differences are due to the presence of a second threonine residue at position 253, which is absent in P450cam. This threonine forms part of the hydrogen bonding network, resulting in subtle structural changes and is also present across the majority of the P450 superfamily. Overall, the results suggest that while the acid-alcohol pair is important for dioxygen activation this process and the method of proton delivery can differ across P450s. Graphic abstract[Figure not available: see fulltext.].
High density scaffolding of functional polymer brushes: Surface initiated atom transfer radical polymerization of active esters
Orski, Sara V.,Fries, Kristen H.,Sheppard, Gareth R.,Locklin, Jason
, p. 2136 - 2143 (2010)
In this Article, we describe a method, for the polymerization of active esters based on N-hydroxysuccinimide 4-vinyl benzoate (NHS4VB) using surface initiated atom, transfer radical polymerization (SI-ATRP). Poly(NHS4VB) brushes have high grafting density and a uniform and smooth morphology, and film thickness increases linearly with reaction time. Block copolymer brushes with 2-hydroxyethyl acrylate, tert-butyl acrylate, and styrene were synthesized, from surface bound poly(NHS4VB) macroinitiators, The active ester brushes show rapid and quantitative conversion under aminolysis conditions with primary amines, which was studied using grazing incidence attenuated total reflection. Fourier transform infrared (GATR-FTIR) and UV-vis spectroscopy. UV-vis was also used to quantify the amount of reactive groups in polymer brush layers of differing thickness. Functionalization of the active ester pendant groups with chromophores containing primary amines showed a linear correlation between the amount of chromophore incorporated, into the brush layer and brush thickness. Grafting densities as high as 25.7 nmol/cm2 were observed for a 50 nm brush. Block copolymer brushes with buried active ester functional moieties also undergo quantitative conversion with primary amines as confirmed by GATR-FTIR, We discuss the potential of activated ester brushes as universal scaffolds for sensor and microarray surfaces, where the twofold, control of functionalizable active ester polymer and block copolymers provides well-ordered, tunable microenvironments.
Precision polyelectrolytes
Srichan, Sansanee,Oswald, Laurence,Zamfir, Mirela,Lutz, Jean-Franois
, p. 1517 - 1519 (2012)
Charged macromolecules with controlled microstructures were prepared. Well-defined non-ionic precursors were first synthesized by sequence-controlled radical polymerization of tert-butyl 4-vinyl benzoate with various N-substituted maleimides. Afterwards, these macromolecules were hydrolyzed into polyanions.
Preparation and Characterization of Some Nickel(II) Tetra-aza Macrocyclic Complexes bearing Pendant Polymerisable Groups as Part of the Ligand Superstructure
Cameron, James H.,Graham, Stephen
, p. 1599 - 1608 (1989)
The synthesis and characterisation of some new nickel(II) macrocyclic complexes of the 'lacunar' type have been performed where the ligand has, as part of the ligand superstructure, either 4-vinylphenyl or allyl groups capable of undergoing polymerisation reactions with selected comonomers.The n.m.r. spectra of a number of these new complexes show them to be fluxional on the n.m.r. time-scale and the nature of this fluxional behaviour is discussed.Some copolymerisation reactions of these complexes, with styrene or methyl methacrylate comonomers, have been performed.
Amphiphilic polymethacrylate- and polystyrene-based chemical delivery systems for damascones
Berthier, Damien,Trachsel, Alain,Fehr, Charles,Ouali, Lahoussine,Herrmann, Andreas
, p. 3089 - 3108 (2005)
Amphiphilic polystyrene- and polymethacrylate-based β-acyloxy ketones were investigated as potential delivery systems for the controlled release of damascones by retro-1,4-addition in applications of functional perfumery. A series of random copolymers being composed of the hydrophobic damascone-release unit and a second hydrophilic monomer were obtained by radical polymerization in organic solution by using 2,2-azobis[2-methylpropanenitrile] (AIBN) as the radical source (Schemes 2 and 3). A first evaluation of the polymer conjugates in acidic or alkaline buffered aqueous solution, and in the presence of a surfactant, showed that polymethacrylates and polystyrenes having a carboxylic acid function as hydrophilic group are particularly interesting for the targeted applications (Table 2). The release of δ-damascone (1) from polymers with poly(methacrylic acid) and poly(vinylbenzoic acid) comonomers in different stoichiometric ratios was thus followed over several days at pH 4, 7, and 9 by comparison of fluorescence probing, solvent extraction, and particle-size measurements (Tables 3 and 4). In acidic media, the polymers were found to be stable, and almost no δ-damascone (1) was released. In neutral or alkaline solution, where the carboxylic acid functions are deprotonated, the concentration of 1 increased over time. In the case of the polymethacrylates, the fluorescence probing experiments showed an increasing hydrophilicity of the polymer backbone with increasing fragrance release, whereas in the case of the polystyrene support, the hydrophilicity of the environment remained constant. These results suggest that the nature of the polymer backbone may have a stronger influence on the fragrance release than the ratio of hydrophilic and hydrophobic monomers in the polymer chain.
Selective Transfer Semihydrogenation of Alkynes with H2O (D2O) as the H (D) Source over a Pd-P Cathode
Liu, Cuibo,Lu, Siyu,Wang, Changhong,Wu, Yongmeng,Zhang, Bin
supporting information, p. 21170 - 21175 (2020/09/11)
We reported a selective semihydrogenation (deuteration) of numerous terminal and internal alkynes using H2O (D2O) as the H (D) source over a Pd-P alloy cathode at a lower potential. P-doping caused the enhanced specific adsorption of alkynes and the promoted intrinsic activity for producing adsorbed atomic hydrogen (H*ads) from water electrolysis. The semihydrogenation of alkynes could be accomplished at a lower potential with up to 99 % selectivity and 78 % Faraday efficiency of alkene products, outperforming pure Pd and commercial Pd/C. This electrochemical semihydrogenation of alkynes might proceed via a H*ads addition pathway rather than a proton-coupled electron transfer process. The decreased amount of H*ads at a lower potential and the more preferential adsorption of the Pd-P to C≡C π bond than C=C moiety resulted in the excellent alkene selectivity. This method was capable of producing mono-, di-, and tri-deuterated alkenes with up to 99 % deuterium incorporation.
Cobalt-Catalyzed Reductive Carboxylation of Aryl Bromides with Carbon Dioxide
Hang, Wei,Yi, Yaping,Xi, Chanjuan
supporting information, p. 2337 - 2341 (2020/04/30)
Cobalt-catalyzed reductive carboxylation of aryl bromides with carbon dioxide has been developed. The reaction proceeded under one atm pressure of CO2 at 40 °C in the presence of cobalt iodide/2,2′-bipyridine catalysts and zinc dust as a reducing reagent. Various aryl bromides could be converted to the corresponding carboxylic acids in good to high yields. Preliminary mechanistic experiments ruled out intervention of intermediate organozinc species for carboxylation with CO2, thus suggesting a direct CO2 insertion into the corresponding ArCoBr species. (Figure presented.).
Pd-Catalyzed Synthesis of Vinyl Arenes from Aryl Halides and Acrylic Acid
Gao, Yang,Ou, Yang,Goo?en, Lukas J.
supporting information, p. 8709 - 8712 (2019/06/17)
Acrylic acid is presented as an inexpensive, non-volatile vinylating agent in a palladium-catalyzed decarboxylative vinylation of aryl halides. The reaction proceeds through a Heck reaction of acrylic acid, immediately followed by protodecarboxylation of the cinnamic acid intermediate. The use of the carboxylate group as a deciduous directing group ensures high selectivity for monoarylated products. The vinylation process is generally applicable to diversely substituted substrates. Its utility is shown by the synthesis of drug-like molecules and the gram-scale preparation of key intermediates in drug synthesis.
Manganese-Catalyzed N-Alkylation of Sulfonamides Using Alcohols
Reed-Berendt, Benjamin G.,Morrill, Louis C.
, p. 3715 - 3724 (2019/03/30)
An efficient manganese-catalyzed N-alkylation of sulfonamides has been developed. This borrowing hydrogen approach employs a well-defined and bench-stable Mn(I) PNP pincer precatalyst, allowing benzylic and simple primary aliphatic alcohols to be employed as alkylating agents. A diverse range of aryl and alkyl sulfonamides undergoes mono-N-alkylation in excellent isolated yields (32 examples, 85% average yield).
Terminal Alkenes from Acrylic Acid Derivatives via Non-Oxidative Enzymatic Decarboxylation by Ferulic Acid Decarboxylases
Aleku, Godwin A.,Prause, Christoph,Bradshaw-Allen, Ruth T.,Plasch, Katharina,Glueck, Silvia M.,Bailey, Samuel S.,Payne, Karl A. P.,Parker, David A.,Faber, Kurt,Leys, David
, p. 3736 - 3745 (2018/08/03)
Fungal ferulic acid decarboxylases (FDCs) belong to the UbiD-family of enzymes and catalyse the reversible (de)carboxylation of cinnamic acid derivatives through the use of a prenylated flavin cofactor. The latter is synthesised by the flavin prenyltransferase UbiX. Herein, we demonstrate the applicability of FDC/UbiX expressing cells for both isolated enzyme and whole-cell biocatalysis. FDCs exhibit high activity with total turnover numbers (TTN) of up to 55000 and turnover frequency (TOF) of up to 370 min?1. Co-solvent compatibility studies revealed FDC's tolerance to some organic solvents up 20 % v/v. Using the in-vitro (de)carboxylase activity of holo-FDC as well as whole-cell biocatalysts, we performed a substrate profiling study of three FDCs, providing insights into structural determinants of activity. FDCs display broad substrate tolerance towards a wide range of acrylic acid derivatives bearing (hetero)cyclic or olefinic substituents at C3 affording conversions of up to >99 %. The synthetic utility of FDCs was demonstrated by a preparative-scale decarboxylation.
