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991.
Jane Luiza Nogueira Fernandes Rodrigo Octavio Mendonça Alves de Souza Rodrigo Bagueira de Vasconcellos Azeredo 《Magnetic resonance in chemistry : MRC》2012,50(6):424-428
In the present investigation, we studied the enzymatic synthesis of monoacylglycerols (MAG) and diacylglycerols (DAG) via the esterification of saturated fatty acids (stearic, palmitic and an industrial residue containing 87% palmitic acid) and glycerol in a solvent‐free system. Three immobilized lipases (Lipozyme RM IM, Lipozyme TL IM and Novozym 435) and different reaction conditions were evaluated. Under the optimal reaction conditions, esterifications catalyzed by Lipozyme RM IM resulted in a mixture of MAG and DAG at high conversion rates for all of the substrates. In addition, except for the reaction of industrial residue at atmospheric pressure, all of these products met the World Health Organization and European Union directives for acylglycerol mixtures for use in food applications. The products were quantified by 13C NMR, with the aid of an external reference signal which was generated from a sealed coaxial tube filled with acetonitrile‐d3. After calibrating the area of this signal using the classical external reference method, the same coaxial tube was used repeatedly to quantify the reaction products. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
992.
Sergey S. Golotvin Rostislav Pol Ryan R. Sasaki Asya Nikitina Philip Keyes 《Magnetic resonance in chemistry : MRC》2012,50(6):429-435
Automated structure verification using 1H NMR data or a combination of 1H and heteronuclear single‐quantum correlation (HSQC) data is gaining more interest as a routine application for qualitative evaluation of large compound libraries produced by synthetic chemistry. The goal of this automated software method is to identify a manageable subset of compounds and data that require human review. In practice, the automated method will flag structure and data combinations that exhibit some inconsistency (i.e. strange chemical shifts, conflicts in multiplicity, or overestimated and underestimated integration values) and validate those that appear consistent. One drawback of this approach is that no automated system can guarantee that all passing structures are indeed correct structures. The major reason for this is that approaches using only 1H or even 1H and HSQC spectra often do not provide sufficient information to properly distinguish between similar structures. Therefore, current implementations of automated structure verification systems allow, in principle, false positive results. Presented in this work is a method that greatly reduces the probability of an automated validation system passing incorrect structures (i.e. false positives). This novel method was applied to automatically validate 127 non‐proprietary compounds from several commercial sources. Presented also is the impact of this approach on false positive and false negative results. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
993.
Błażej Gierczyk Wojciech Ostrowski Marcin Kaźmierczak 《Magnetic resonance in chemistry : MRC》2012,50(4):271-277
2‐Aryl‐1,3,4‐selenadiazoles were studied by 1H, 13C, 15N and 77Se NMR spectroscopy. The results (chemical shifts and coupling constants) were correlated with Hammett substituent parameters as well as calculated chemical shifts and bond lengths. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
994.
Cheng‐Xiong Liu Zhi‐yong Guo Yan‐Hong Xue Hong‐Yan Zhang Hong‐Qi Zhang Kun Zou Nian‐Yu Huang 《Magnetic resonance in chemistry : MRC》2012,50(4):320-324
Three new steroidal compounds with polyhydroxy groups, tupisteroide A–C (1–3), were obtained from the roots of Tupistra chinensis, together with one known compound (4) that was isolated from this plant for the first time. The structures of tupisteroide A–C were determined on the basis of one‐ and two‐dimensional NMR spectroscopy, including 1H–1H Correlation Spectroscopy, Heteronuclear Multiple Bond Correlation, and Heteronuclear Single Quantum Coherence experiments. The isolated compounds were evaluated for their cytotoxic activities against A549, HepG2, and CaSki cancer cell lines in vitro. Among them, compounds 1, 2, and 4 did not show significant inhibitory activity, but compound 3 showed cytotoxicity against A549 cancer cell lines with IC50 values of 25.0 μM. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
995.
Ly Dieu Ha Poul Erik Hansen Fritz Duus Hung Dinh Pham Lien‐Hoa D. Nguyen 《Magnetic resonance in chemistry : MRC》2012,50(3):242-245
Four new prenylated depsidones, oliveridepsidones A–D, were isolated from the bark of Garcinia oliveri collected in Vietnam. Their structures were elucidated using mainly NMR techniques (1H and 13C NMR, HMQC, HMBC and NOE experiments). Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
996.
Dr. Michael L. Lejkowski Dr. Ronald Lindner Dr. Takeharu Kageyama Dr. Gabriella É. Bódizs Dipl.‐Chem. Philipp N. Plessow Dr. Imke B. Müller Dr. Ansgar Schäfer Dr. Frank Rominger Prof. Dr. Peter Hofmann Dr. Cornelia Futter Dr. Stephan A. Schunk Dr. Michael Limbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(44):14017-14025
For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C1 building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we describe a homogeneous catalyst based on nickel that permits the catalytic synthesis of the industrially highly relevant acrylate sodium acrylate from CO2, ethylene, and a base, as demonstrated, at this stage, by a turnover number of greater than 10 with respect to the metal. 相似文献
997.
We propose a new two-component geodesic equation with the unusual property that the underlying space has constant positive curvature. In the special case of one space dimension, the equation reduces to the two-component Hunter–Saxton equation. 相似文献
998.
Co (II)‐C12 alkyl carbon chain multi‐functional ionic liquid immobilized on nano‐SiO2 nano‐SiO2@CoCl3‐C12IL as an efficient cooperative catalyst for C–H activation by direct acylation of aryl halides with aldehydes
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Nano‐silica supported ionic liquids composed of alkyl carbon chain and transition metal chlorides anions have been prepared and successfully applied as a heterogeneous catalyst in the direct aldehyde C‐H activation. Catalytic results indicated that nano‐SiO2 supported ionic liquid consisting C12 alkyl carbon chain and CoCl3 anion nano‐SiO2@CoCl3‐C12IL showed excellent catalytic properties with good to excellent yields towards the desired aryl ketones. The excellent recyclability of the supported catalyst, mild reaction conditions, low catalyst loading, and operational simplicity are the important features of this methodology. 相似文献
999.
Discrete and continuous non-intersecting random processes have given rise to critical “infinite-dimensional diffusions”, like the Airy process, the Pearcey process and variations thereof. It has been known that domino tilings of very large Aztec diamonds lead macroscopically to a disordered region within an inscribed ellipse (arctic circle in the homogeneous case), and a regular brick-like region outside the ellipse. The fluctuations near the ellipse, appropriately magnified and away from the boundary of the Aztec diamond, form an Airy process, run with time tangential to the boundary. 相似文献
1000.
A novel heterogeneous nanocatalyst: 2‐Methoxy‐1‐phenylethanone functionalized MCM‐41 supported Cu(II) complex for C‐S coupling of aryl halides with thiourea
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An environmentally friendly copper‐based catalyst supported on 2‐Methoxy‐1‐phenylethanone functionalized MCM‐41 was prepared and characterized by FT‐IR, FE‐SEM, TEM, XRD, EDX, BET and ICP techniques. The catalyst was applied for the C?S cross‐coupling reaction of aryl halides with thiourea. Corresponding products were produced in good yields in aerobic conditions. The catalyst could be recovered and recycled for several times. 相似文献