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排序方式: 共有91条查询结果,搜索用时 140 毫秒
31.
Patricia Gomez de Santos Alejandro González-Benjumea Angela Fernandez-Garcia Carmen Aranda Yinqi Wu Andrada But Patricia Molina-Espeja Diana M. Maté David Gonzalez-Perez Wuyuan Zhang Jan Kiebist Prof. Katrin Scheibner Prof. Martin Hofrichter Katarzyna Świderek Prof. Vicent Moliner Prof. Julia Sanz-Aparicio Prof. Frank Hollmann Prof. Ana Gutiérrez Prof. Miguel Alcalde 《Angewandte Chemie (International ed. in English)》2023,62(9):e202217372
The hydroxylation of fatty acids is an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. In this study, we have engineered a highly regioselective fungal peroxygenase for the ω-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutation near the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward subterminal hydroxylation with a drop in the over-oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced by Pichia pastoris at 0.4 g L−1 in a fed-batch bioreactor and used in the preparative synthesis of 1.4 g of (ω-1)-hydroxytetradecanoic acid with 95 % regioselectivity and 83 % ee for the S enantiomer. 相似文献
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Dennis Rottschäfer Beate Neumann Dr. Hans‐Georg Stammler Dr. Maurice van Gastel Dr. Diego M. Andrada Priv.‐Doz. Dr. Rajendra S. Ghadwal 《Angewandte Chemie (International ed. in English)》2018,57(17):4765-4768
One‐electron reduction of C2‐arylated 1,3‐imidazoli(ni)um salts (IPrAr)Br (Ar=Ph, 3 a ; 4‐DMP, 3 b ; 4‐DMP=4‐Me2NC6H4) and (SIPrAr)I (Ar=Ph, 4 a ; 4‐Tol, 4 b ) derived from classical NHCs (IPr=:C{N(2,6‐iPr2C6H3)}2CHCH, 1 ; SIPr=:C{N(2,6‐iPr2C6H3)}2CH2CH2, 2 ) gave radicals [(IPrAr)]. (Ar=Ph, 5 a ; 4‐DMP, 5 b ) and [(SIPrAr)]. (Ar=Ph, 6 a ; 4‐Tol, 6 b ). Each of 5 a , b and 6 a , b exhibited a doublet EPR signal, a characteristic of monoradical species. The first solid‐state characterization of NHC‐derived carbon‐centered radicals 6 a , b by single‐crystal X‐ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent aryl group. 相似文献
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Observation of Main‐Group Tricarbonyls [B(CO)3] and [C(CO)3]+ Featuring a Tilted One‐Electron Donor Carbonyl Ligand 下载免费PDF全文
Jiwen Jian Jiaye Jin Hui Qu Dr. Hailu Lin Dr. Mohua Chen Dr. Guanjun Wang Prof. Mingfei Zhou Dr. Diego M. Andrada Dr. Markus Hermann Prof. Gernot Frenking 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2376-2385
A combined experimental and theoretical study on the main‐group tricarbonyls [B(CO)3] in solid noble‐gas matrices and [C(CO)3]+ in the gas phase is presented. The molecules are identified by comparing the experimental and theoretical IR spectra and the vibrational shifts of nuclear isotopes. Quantum chemical ab initio studies suggest that the two isoelectronic species possess a tilted η1(μ1‐CO)‐bonded carbonyl ligand, which serves as an unprecedented one‐electron donor ligand. Thus, the central atoms in both complexes still retain an 8‐electron configuration. A thorough analysis of the bonding situation gives quantitative information about the donor and acceptor properties of the different carbonyl ligands. The linearly bonded CO ligands are classical two‐electron donors that display classical σ‐donation and π‐back‐donation following the Dewar–Chatt–Duncanson model. The tilted CO ligand is a formal one‐electron donor that is bonded by σ‐donation and π‐back‐donation that involves the singly occupied orbital of the radical fragments [B(CO)2] and [C(CO)2]+. 相似文献
35.
Extended VIKOR method in comparison with outranking methods 总被引:1,自引:0,他引:1
The VIKOR method was developed to solve MCDM problems with conflicting and noncommensurable (different units) criteria, assuming that compromising is acceptable for conflict resolution, the decision maker wants a solution that is the closest to the ideal, and the alternatives are evaluated according to all established criteria. This method focuses on ranking and selecting from a set of alternatives in the presence of conflicting criteria, and on proposing compromise solution (one or more). The VIKOR method is extended with a stability analysis determining the weight stability intervals and with trade-offs analysis. The extended VIKOR method is compared with three multicriteria decision making methods: TOPSIS, PROMETHEE, and ELECTRE. A numerical example illustrates an application of the VIKOR method, and the results by all four considered methods are compared. 相似文献
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The current–voltage characteristics and photoresponse of mesa structured {111}‐oriented homoepitaxial CVD diamond p(i)n‐junctions with different intrinsic layer thickness are investigated. When a sufficiently thick intrinsic layer is present, a rectification ratio of 108 at ±10 V could be obtained. Good rectifying diodes show a high photoresponse ratio between 210 nm (above bandgap) and 500 nm (below bandgap), making them suitable for UV detection purposes. The results are compared with similar measurements carried out on polycrystalline CVD diamond pn‐junctions.
39.
Mateo Alajarín Prof. Carmen López‐Leonardo Dr. Ángel Álvarez‐García Pilar Llamas‐Lorente Dr. Pilar Sánchez‐Andrada Dr. José Berná Dr. Aurelia Pastor Dr. Delia Bautista Dr. Peter G. Jones Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(12):3728-3735
A series of N,P,P‐trisubstituted aminophosphanes react with diphenylcyclopropenone to afford an easily separable mixture of two diastereomeric α,β‐diphenyl‐β‐phosphinoyl carboxamides in good yields. X‐ray crystal structures reveal that these compounds associate into dimers, formed from two enantiomeric units linked by two bifurcated hydrogen bonds, whereby the oxygen atom of the phosphoryl group acts as a dual acceptor for the vicinal NH and CH of a carbonyl group of a neighbouring molecule. Studies on the interconversion between diastereomeric phosphinoyl carboxamides in basic solution show that the thermodynamically most stable isomer depends on the nature of the substituent at the nitrogen atom. Simple computational calculations explain this phenomenon. 相似文献
40.
J. C. Garro Martinez M. F. Andrada M. R. Estrada E. A. Castro G. N. Zamarbide Z. Mucsi I. G. Csizmadia 《Journal of Physical Organic Chemistry》2008,21(5):409-418
A general structure, substituent and activity relationship of the following type has been fitted to the available ED50 values of cyclic enaminone antiepileptic compounds: . In this relationship ‘structure’ was quantified by d, the distance measured between the carbonyl oxygen and the first atom of the aromatic ring. The ‘substituent’ was quantified by Hammett substituent constant: (σ). With the aid of the above function of two independent variables, a new molecular structure was predicted by extrapolation that has shown about two orders of magnitude greater activity than the most active molecule in the original set with measured ED50 values. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献