91751-55-2Relevant academic research and scientific papers
The Mechanism of Dehydrating Bimodules in trans-Acyltransferase Polyketide Biosynthesis: A Showcase Study on Hepatoprotective Hangtaimycin
Deng, Zixin,Dickschat, Jeroen S.,Dong, Yulu,Lu, Junlei,Luo, Minghe,Qi, Miaomiao,Shen, Kun,Sun, Guo,Sun, Yuhui,Tang, Lingjie,Xiang, Jin,Xu, Houchao,Yin, Zhiyong
supporting information, p. 19139 - 19143 (2021/08/03)
A bioassay-guided fractionation led to the isolation of hangtaimycin (HTM) from Streptomyces spectabilis CCTCC M2017417 and the discovery of its hepatoprotective properties. Structure elucidation by NMR suggested the need for a structural revision. A putative HTM degradation product was also isolated and its structure was confirmed by total synthesis. The biosynthetic gene cluster was identified and resembles a hybrid trans-AT PKS/NRPS biosynthetic machinery whose first PKS enzyme contains an internal dehydrating bimodule, which is usually found split in other trans-AT PKSs. The mechanisms of such dehydrating bimodules have often been proposed, but have never been deeply investigated. Here we present in vivo mutations and in vitro enzymatic experiments that give first and detailed mechanistic insights into catalysis by dehydrating bimodules.
Enantioselective and Diastereodivergent Synthesis of Spiroindolenines via Chiral Phosphoric Acid-Catalyzed Cycloaddition
Gandon, Vincent,Masson, Géraldine,Mati?i?, Mateja,Neuville, Luc,Van Elslande, Elsa,Varlet, Thomas
supporting information, p. 11611 - 11619 (2021/08/16)
A diastereodivergent and enantioselective synthesis of chiral spirocyclohexyl-indolenines with four contiguous stereogenic centers is achieved by a chiral phosphoric acid-catalyzed cycloaddition of 2-susbtituted 3-indolylmethanols with 1,3-dienecarbamates. Modular access to two different diastereoisomers with high enantioselectivities was obtained by careful choice of reaction conditions. Their functional group manipulation provides an efficient access to enantioenriched spirocyclohexyl-indolines and -oxindoles. The origins of this stereocontrol have been identified using DFT calculations, which reveal an unexpected mechanism compared to our previous work dealing with enecarbamates.
Preparation method of gamma-substituted hexadienoic acid
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Paragraph 0019, (2021/01/20)
The invention relates to a preparation method of gamma-substituted hexadienoic acid. The method is characterized by comprising the following steps: (1) at -10-40 DEG C, adding a solvent, a catalyst and a catalytic assistant into a reaction vessel, stirring, introducing oxygen, adding 1-(2-furyl)-1-alkyl methanol, controlling the molar ratio of the catalyst to the catalytic assistant to the 1-(2-furyl)-1-alkyl methanol at 0.0001-5:0.0001-3:100, reacting at 0-200 DEG C under 0.1-20 MPa for 1-74 h, wherein the solvent is a mixed solution composed of a water phase and an organic phase according toa volume ratio of 1:0.01-3, the water phase is a phosphate acidic solution, the organic phase is a reaction inert solvent, the catalyst is a palladium compound, and the catalytic assistant is an amine or phosphine compound; and (2) cooling the reaction vessel to room temperature, adding an organic solvent, extracting, and carrying out reduced pressure distillation on the organic phase. The methodhas the advantages that the defect of technical economy in an existing synthesis route is overcome, the technological process is simplified, consumption and emission are reduced, energy consumption and cost are reduced, and the method is suitable for industrial production for increasing productivity.
Ether-functionalized ionic liquids for nonaqueous biocatalysis: Effect of different cation cores
Zhao, Hua,Kanpadee, Naphatsawan,Jindarat, Chanida
, p. 104 - 112 (2019/03/28)
Ether-functionalized ionic liquids (ILs) usually have low viscosities, and can be designed to be compatible with enzymes. However, there is a lack of understanding of the effect of different ether-functionalized structures on the enzyme activity. We systematically evaluated new ether-functionalized ILs carrying different cation cores (pairing with Tf2N? anions) in two Novozym 435-catalyzed reactions: (1) the transesterification of ethyl sorbate with 1-propanol at 50 °C; (2) the ring-opening polymerization (ROP) of ε-caprolactone at 70 °C. The lipase showed different activities: in the first reaction, [CH3OCH2CH2-Et3N][Tf2N] and [CH3OCH2CH2-Py][Tf2N] gave the highest reaction rates; in the second reaction, [CH3OCH2CH2-PBu3][Tf2N] produced the highest molecular mass (Mw up to 25,400 Da). The lipase's thermal stability in [CH3OCH2CH2-Et3N][Tf2N] was found much higher than that in t-butanol. The fluorescence spectra of free lipase (excited at 280 nm) in these ILs reveal that the wavelength of the maximum emission peak occurred at 314 nm for both [CH3OCH2CH2PBu3][Tf2N] and [CH3OCH2CH2PEt3][Tf2N], which matched closely with that (313 nm) in aqueous phosphate buffer (pH 7.5, 20 mM), while other ether-functionalized ILs led to various degrees of red shifts. In summary, the lipase activity is not only dependent on the IL structure, but also on the substrate and other reaction conditions.
Iron-Catalyzed Reactions of 2-Pyridone Derivatives: 1,6-Addition and Formal Ring Opening/Cross Coupling
Huang, Lin,Gu, Yiting,Fürstner, Alois
, p. 4017 - 4023 (2019/08/07)
In the presence of simple iron salts, 2-pyridone derivatives react with Grignard reagents under mild conditions to give the corresponding 1,6-addition products; if the reaction medium is supplemented with an aprotic dipolar cosolvent after the actual addition step, the intermediates primarily formed succumb to ring opening, giving rise to non-thermodynamic Z,E-configured dienoic acid amide derivatives which are difficult to make otherwise. Control experiments as well as the isolation and crystallographic characterization of a (tricarbonyl)iron pyridone complex suggest that the active iron catalyst generated in situ exhibits high affinity to the polarized diene system embedded into the heterocyclic ring system of the substrates, which likely serves as the actual recognition element.
An Efficient Aerobic Oxidation Protocol of Aldehydes to Carboxylic Acids in Water Catalyzed by an Inorganic-Ligand-Supported Copper Catalyst
Yu, Han,Ru, Shi,Zhai, Yongyan,Dai, Guoyong,Han, Sheng,Wei, Yongge
, p. 1253 - 1257 (2018/02/16)
A method for the aerobic oxidation of aldehydes to carboxylic acids in water by using an inorganic-ligand-supported copper catalyst was developed. This method was performed with the use of atmospheric oxygen as the sole oxidant under extremely mild aqueous conditions, and furthermore, a wide range of aldehydes with various functional groups were tolerated. The copper catalyst could be recycled and used in successive reactions at least six times without any appreciable degradation in performance. This method is operationally simple and avoids the use of high-costing, toxic, air/moisture-sensitive, and commercially unavailable organic ligands. The generality of this method gives it potential to be used on the industrial scale.
A colourful azulene-based protecting group for carboxylic acids
Bevan, Thomas W.,Francis-Taylor, James,Wong, Helena,Northcote, Peter T.,Harvey, Joanne E.
supporting information, p. 2942 - 2955 (2018/05/16)
An intensely blue-coloured protecting group for carboxylic acids has been developed. The protecting group is introduced through a Steglich esterification that couples 6-(2-hydroxyethyl)azulene (AzulE) and the carboxylic acid substrate. Deprotection is effected under basic conditions by the addition of the amidine base DBU, whereupon cleavage occurs, accompanied by a colour change. A two-step deprotection methodology comprising activation with oxalyl chloride and deprotection with a very mild base was developed for use with base-sensitive substrates. The AzulE esters were found to be compatible with other commonly employed protecting groups – silyl ethers, MOM acetals – by studying their orthogonal and concomitant deprotections. The stability of the new protecting group towards various synthetic processes – oxidation, reduction, cross-coupling, olefination and treatment with base – provided the basis of a versatility profile. This indicated that AzulE esters are sensitive to strongly oxidising and basic agents while being compatible with reducing conditions and selected other reactions. The convenience of a highly coloured protecting group for tracking material (and avoiding loss of compound) through laboratory processes warrants further investigation of this and/or related species.
An Efficient Iron(III)-Catalyzed Aerobic Oxidation of Aldehydes in Water for the Green Preparation of Carboxylic Acids
Yu, Han,Ru, Shi,Dai, Guoyong,Zhai, Yongyan,Lin, Hualin,Han, Sheng,Wei, Yongge
, p. 3867 - 3871 (2017/03/27)
The first example of a heterogeneous iron(III)-catalyzed aerobic oxidation of aldehydes in water was developed. This method utilizes 1 atmosphere of oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. Its operational simplicity, gram-scale oxidation, and the ability to successively reuse the catalyst, make this new methodology environmentally benign and cost effective. The generality of this methodology gives it the potential to be used on an industrial scale.
Enantioselective Synthesis of N?H-Free 1,5-Benzothiazepines
Wang, Guojin,Tang, Yu,Zhang, Yu,Liu, Xiaohua,Lin, Lili,Feng, Xiaoming
supporting information, p. 554 - 557 (2017/01/18)
An enantioselective sulfa-Michael-cyclization reaction was developed for the synthesis of 1,5-benzothiazepines with versatile pharmacological activities. The reaction between 2-aminothiophenol and α,β-unsaturated pyrazoleamides gave direct access to N?H-free 1,5-benzothiazepines in the presence of a chiral N,N′-dioxide/Yb(OTf)3complex. Excellent enantioselectivities (up to 96 % ee) and high yields (up to 99 %) were obtained for a broad range of substrates under mild reaction conditions. This method provided a facile approach to the antidepressant drug (R)-(?)-Thiazesim.
Solar lab and pilot scale photo-oxidation of ethylparaben using H2O2 and TiO2 in aqueous solutions
Zú?iga-Benítez, Henry,Pe?uela, Gustavo A.
, p. 62 - 70 (2017/02/05)
Ethylparaben (Eth-PB) is one of the most used parabens for preservation of many personal care products and food. However, a number of scientific studies have indicated that this compound could interfere with the endocrine or hormonal system of different living beings, which along with data about its presence in different water bodies generates the necessity of seeking alternatives to minimize the potential negative effect of this situation. In this way, removal of Eth-PB using heterogeneous photocatalysis with TiO2, hydrogen peroxide and light radiation (solar spectrum: wavelength >290 nm) was assessed, considering the individual effects of different operational parameters like the catalyst and H2O2 dosages, the pH and the pollutant initial concentration. According to this, conditions that, under the experimental range, promote a higher paraben elimination were established. Tests were carried out at lab-scale using a photo-simulator equipped with a Xenon lamp, and at pilot scale (volume treated ～100 L) using a compound parabolic collector and direct solar light radiation. In both cases, more than a 80% of substrate elimination was reached in less than 6 h of reaction, demonstrating the effectiveness of the photocatalytic system to remove this kind of compounds. Additionally, a significant reduction of the total organic carbon present in the solutions, and an increment of the biodegradability of the samples were appreciated. Finally, some of the by-products generated during the contaminant removal were identified.
