Ultrasound-assisted lipase catalyzed hydrolysis of aspirin methyl ester

Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.ultsonch.2017.08.004.The ultrasound-assisted hydrolysis of aspirin methyl ester (AME) was investigated using immobilized Candida antarctica lipase B (CALB) (1%) in the presence of solvents like triolein, chloroform (CHCl3) and dichloromethane (DCM). The effect of ultrasound and the role of water on the conversion rates have also been investigated. Proton nuclear magnetic resonance spectroscopic (1H NMR) was chosen to calculate hydrolysis convertion rates. We observed that lipase-ultrasound assisted hydrolysis of AME in the presence of triolein and water showed the highest hydrolysis conversion rate (65.3%). Herein low water amount played an important role as a nucleophile being crucial for the hydrolysis yields obtained. Lipase activity was affected by the conjugated action of ultrasound and solvents (35.75% of decrease), however not disturbing its hydrolytic efficiency. It was demonstrated that lipase is able to hydrolyse AME to methyl 2-hydroxy benzoate (methyl salicylate), which applications include fragrance agents in food, beverages and cosmetics, or analgesic agent in liniments.All authors gratefully acknowledge the financial support provided by International Joint Research Laboratory for Textile and Fibre Bioprocesses at Jiangnan University. The authors are also thankful to the Department of Oils, Oleochemicals and Surfactants technology, Institute of Chemical Technology, Mumbai, India and to the Bioprocess and Bio nanotechnology Research Group (BBRG) of University of Minho. Authors would like also to acknowledge the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE01-0145-FEDER-000004) funded by European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte and to the Fundamental Research Funds for the Central Universities (No. JUSRP51622 A and No. JUSRP115A03), and to the Jiangsu Province Scientific Research Innovation Project for Academic Graduate Students in 2016 (No. KYLX16_0788).info:eu-repo/semantics/publishedVersio

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Aspherical-Atom modeling of coordination compounds by single-crystal X-ray diffraction allows the correct metal atom to be identified

Single-crystal X-ray diffraction (XRD) is often considered the gold standard in analytical chemistry, as it allows element identification as well as determination of atom connectivity and the solid-state structure of completely unknown samples. Element assignment is based on the number of electrons of an atom, so that a distinction of neighboring heavier elements in the periodic table by XRD is often difficult. A computationally efficient procedure for aspherical-atom least-squares refinement of conventional diffraction data of organometallic compounds is proposed. The iterative procedure is conceptually similar to Hirshfeld-atom refinement (Acta Crystallogr. Sect. A­ 2008, 64, 383–393; IUCrJ. 2014, 1,61–79), but it relies on tabulated invariom scattering factors (Acta Crystallogr. Sect. B­ 2013, 69, 91–104) and the Hansen/Coppens multipole model; disordered structures can be handled as well. Five linear-coordinate 3d metal complexes, for which the wrong element is found if standard independent-atom model scattering factors are relied upon, are studied, and it is shown that only aspherical-atom scattering factors allow a reliable assignment. The influence of anomalous dispersion in identifying the correct element is investigated and discussed

Lewis Base Stabilized Group 14 Metalylenes

The chemistry of stable metalylenes (the heavier group 14 element analogues of carbenes) is an intriguing target of main group chemistry due to their synthetic potential and industrial application. In the present study, we report on the utilization of an abnormal N-heterocyclic carbene (aNHC) and a cyclic alkyl-amino carbene (cAAC) as a Lewis base for the syntheses of compounds aNHC·SiCl₂ (<b>3</b>), aNHC·SnCl₂ (<b>4</b>), and cAAC·SnCl₂ (<b>5</b>). The synthesis of silylene <b>3</b> involved the ligand-substitution reaction between NHC·SiCl₂ and an aNHC. However, compounds <b>4</b> and <b>5</b> were synthesized by the reactions of aNHC and cAAC with SnCl₂ in the molar ratio of 1:1. Compounds <b>3</b>–<b>5</b> are well-characterized with various spectroscopic methods and single-crystal X-ray structural analysis

Lewis Base Stabilized Group 14 Metalylenes

The chemistry of stable metalylenes (the heavier group 14 element analogues of carbenes) is an intriguing target of main group chemistry due to their synthetic potential and industrial application. In the present study, we report on the utilization of an abnormal N-heterocyclic carbene (aNHC) and a cyclic alkyl-amino carbene (cAAC) as a Lewis base for the syntheses of compounds aNHC·SiCl₂ (<b>3</b>), aNHC·SnCl₂ (<b>4</b>), and cAAC·SnCl₂ (<b>5</b>). The synthesis of silylene <b>3</b> involved the ligand-substitution reaction between NHC·SiCl₂ and an aNHC. However, compounds <b>4</b> and <b>5</b> were synthesized by the reactions of aNHC and cAAC with SnCl₂ in the molar ratio of 1:1. Compounds <b>3</b>–<b>5</b> are well-characterized with various spectroscopic methods and single-crystal X-ray structural analysis

Oxidative Addition Versus Substitution Reactions of Group 14 Dialkylamino Metalylenes with Pentafluoropyridine

Dialkylamino compounds of group 14 elements (Si, Ge, Sn) in the +2 oxidation state supported by benzamidinate ligands were synthesized and treated with pentafluoropyridine. Two different modes of reactivity were observed, depending on the metal atom and the basicity of the substituent at the metal. Pentafluoropyridine undergoes oxidative addition reaction at the Si­(II) and Ge­(II) atoms whereas at the Sn­(II) atom substitution of the NMe₂ group by the para fluorine of pentafluoropyridine occurs. The C–F bond activation by the lone pair of germanium is the first report of this kind. The Sn­(II) fluoride obtained has an elongated Sn–F bond length and can be used as a good fluorinating agent. The compounds were characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray structural analysis. Single crystal X-ray structural analysis of the tin fluoride shows an asymmetric dimer with weak interactions

Oxidative Addition Versus Substitution Reactions of Group 14 Dialkylamino Metalylenes with Pentafluoropyridine

Dialkylamino compounds of group 14 elements (Si, Ge, Sn) in the +2 oxidation state supported by benzamidinate ligands were synthesized and treated with pentafluoropyridine. Two different modes of reactivity were observed, depending on the metal atom and the basicity of the substituent at the metal. Pentafluoropyridine undergoes oxidative addition reaction at the Si­(II) and Ge­(II) atoms whereas at the Sn­(II) atom substitution of the NMe₂ group by the para fluorine of pentafluoropyridine occurs. The C–F bond activation by the lone pair of germanium is the first report of this kind. The Sn­(II) fluoride obtained has an elongated Sn–F bond length and can be used as a good fluorinating agent. The compounds were characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray structural analysis. Single crystal X-ray structural analysis of the tin fluoride shows an asymmetric dimer with weak interactions

A Singlet Biradicaloid Zinc Compound and Its Nonradical Counterpart

Metal ions with radical centers in their coordination sphere are key participants in biological and catalytic processes. In the present study, we describe the synthesis of the cAAC:ZnCl₂ adduct (<b>1</b>) using a cyclic alkylaminocarbene (cAAC) as donor ligand. Compound <b>1</b> was treated with 2 equiv of KC₈ and LiB­(<i>sec-</i>Bu)₃H to yield a deep blue-colored dicarbene zinc compound (cAAC)₂Zn (<b>2</b>) and the colorless hydrogenated zinc compound (cAACH)₂Zn (<b>3</b>), respectively. Compounds <b>2</b> and <b>3</b> were well characterized by spectroscopic methods and single-crystal X-ray structural analysis. Density functional theory calculations were performed for <b>2</b> which indicate that this molecule possesses a singlet biradicaloid character. Moreover, we show the application of <b>2</b> in CO₂ activation, which yields a zwitterionic cAAC·CO₂ adduct

A Singlet Biradicaloid Zinc Compound and Its Nonradical Counterpart

Metal ions with radical centers in their coordination sphere are key participants in biological and catalytic processes. In the present study, we describe the synthesis of the cAAC:ZnCl₂ adduct (<b>1</b>) using a cyclic alkylaminocarbene (cAAC) as donor ligand. Compound <b>1</b> was treated with 2 equiv of KC₈ and LiB­(<i>sec-</i>Bu)₃H to yield a deep blue-colored dicarbene zinc compound (cAAC)₂Zn (<b>2</b>) and the colorless hydrogenated zinc compound (cAACH)₂Zn (<b>3</b>), respectively. Compounds <b>2</b> and <b>3</b> were well characterized by spectroscopic methods and single-crystal X-ray structural analysis. Density functional theory calculations were performed for <b>2</b> which indicate that this molecule possesses a singlet biradicaloid character. Moreover, we show the application of <b>2</b> in CO₂ activation, which yields a zwitterionic cAAC·CO₂ adduct

A Singlet Biradicaloid Zinc Compound and Its Nonradical Counterpart

Metal ions with radical centers in their coordination sphere are key participants in biological and catalytic processes. In the present study, we describe the synthesis of the cAAC:ZnCl₂ adduct (<b>1</b>) using a cyclic alkylaminocarbene (cAAC) as donor ligand. Compound <b>1</b> was treated with 2 equiv of KC₈ and LiB­(<i>sec-</i>Bu)₃H to yield a deep blue-colored dicarbene zinc compound (cAAC)₂Zn (<b>2</b>) and the colorless hydrogenated zinc compound (cAACH)₂Zn (<b>3</b>), respectively. Compounds <b>2</b> and <b>3</b> were well characterized by spectroscopic methods and single-crystal X-ray structural analysis. Density functional theory calculations were performed for <b>2</b> which indicate that this molecule possesses a singlet biradicaloid character. Moreover, we show the application of <b>2</b> in CO₂ activation, which yields a zwitterionic cAAC·CO₂ adduct