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41.
Anaïs Geny Dr. Nicolas Agenet Dr. Laura Iannazzo Max Malacria Prof. Dr. Corinne Aubert Dr. Vincent Gandon Dr. 《Angewandte Chemie (International ed. in English)》2009,48(10):1810-1813
Cobalt cyclopentadienyl complexes incorporating a fumarate and a CO ligand (see picture) efficiently catalyze inter‐ and intramolecular [2+2+2] cycloadditions of alkynes, nitriles, and/or alkenes to give benzenes, pyridines, or 1,3‐cyclohexadienes. Unlike catalysts such as [CpCo(CO)2] or [CpCo(C2H4)2] (Cp=C5H5), they are air‐stable, easy to handle, compatible with microwave conditions, and do not necessarily require irradiation to be active.
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Christian R. Zwick Max B. Sosa Hans Renata 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19030-19034
The GE81112 tetrapeptides are a small family of unusual nonribosomal peptide congeners with potent inhibitory activity against prokaryotic translation initiation. With the exception of the 3‐hydroxy‐l ‐pipecolic acid unit, little is known about the biosynthetic origins of the non‐proteinogenic amino acid monomers of the natural product family. Here, we elucidate the biogenesis of the 4‐hydroxy‐l ‐citrulline unit and establish the role of an iron‐ and α‐ketoglutarate‐dependent enzyme (Fe/αKG) in the pathway. Homology modelling and sequence alignment analysis further facilitate the rational engineering of this enzyme to become a specific 4‐arginine hydroxylase. We subsequently demonstrate the utility of this engineered enzyme in the synthesis of a dipeptide fragment of the antibiotic enduracidin. This work highlights the value of applying a bioinformatics‐guided approach in the discovery of novel enzymes and engineering of new catalytic activity into existing ones. 相似文献
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Stíbr B Holub J Bakardjiev M Pavlík I Tok OL Císarová I Wrackmeyer B Herberhold M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(10):2239-2244
The reaction of nido-[7,8,9-PC(2)B(8)H(11)] (1) with [[CpFe(CO)(2)](2)] (Cp=eta(5)-C(5)H(5) (-)) in benzene (reflux, 3 days) gave an eta(1)-bonded complex [7-Fp-(eta(1)-nido-7,8,9,-PC(2)B(8)H(10))] (2; Fp=CpFe(CO)(2); yield 38 %). A similar reaction at elevated temperatures (xylene, reflux 24 h) gave the isomeric complex [7-Fp-(eta(1)-nido-7,9,10-PC(2)B(8)H(10))] (3; yield 28 %) together with the fully sandwiched complexes [1-Cp-closo-1,2,4,5-FePC(2)B(8)H(10)] 4 a (yield 30%) and [1-Cp-closo-1,2,4,8-FePC(2)B(8)H(10)] 4 b (yield 5%). Compounds 2 and 3 are isolable intermediates along the full eta(5)-complexation pathway of the phosphadicarbaborane cage; their heating (xylene, reflux, 24 h) leads finally to the isolation of compounds 4 a (yields 46 and 52%, respectively) and 4 b (yields 4 and 5%, respectively). Moreover, compound 3 is isolated as a side product from the heating of 2 (yield 10%). The structure of compound 4 a was determined by an X-ray structural analysis and the constitution of all compounds is consistent with the results of mass spectrometry and IR spectroscopy. Multinuclear ((1)H, (11)B, (31)P, and (13)C), two-dimensional [(11)B-(11)B]-COSY, and (1)H[(11)B(selective)] magnetic resonance measurements led to complete assignments of all resonances and are in excellent agreement with the structures proposed. 相似文献
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Anne-Marie Caminade Fayez El Khatib Antoine Baceiredo Max Koenig 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2-4):365-367
Abstract The ozonization of various halophosphines 1a-j leads with quantitative yields to the corresponding phosphine oxides 2a-j. Ozonization is a convenient method of oxidation, in particular of compounds with bulky ligands (1c, 1d, 1e). 相似文献
48.
Voinov VG Deinzer ML Beckman JS Barofsky DF 《Journal of the American Society for Mass Spectrometry》2011,22(4):607-611
Recently, we demonstrated that a radio-frequency-free electromagnetostatic (rf-free EMS) cell could be retrofitted into a
triple quad mass spectrometer to allow electron-capture dissociation (ECD) without the aid of cooling gas or phase-specific
electron injection into the cell (Voinov et al., Rapid Commun Mass Spectrom 22, 3087–3088, 2008; Voinov et al., Anal Chem 81, 1238–1243, 2009). Subsequently, we used our rf-free EMS cell in the same instrument platform to demonstrate ECD occurring in the same space
and at the same time with collision-induced dissociation (CID) to produce golden pairs and even triplets from peptides (Voinov
et al., Rapid Commun Mass Spectrom 23, 3028–3030, 2009). In this report, we demonstrate that ECD and CID product-ion mass spectra can be recorded at high resolution with flexible
control of fragmentation processes using a newly designed cell installed in a hybrid Q-TOF tandem mass spectrometer. 相似文献
49.
Setzer MJ 《Journal of colloid and interface science》2001,235(1):170-182
In contrast to the triple-point condition of bulk material, condensed matter in porous media can coexist stably as liquid, solid, and vapor over a wide temperature range. The necessary conditions are found by a thermodynamic approach starting with the potential which reflects the grand canonical distribution and is characterized by heat and matter exchange. The other parameters are volume and surface. Therefore, it is designated the free mechanical potential. General expressions for mechanical stability are given. On condensation and melting the nonwetting phases vanish. These are thermodynamically stable phase transitions. For the opposing effects evaporation and fusion, an energy barrier must be transgressed either by nucleation or by intrusion as discussed here. These are metastable states. Phase transitions are the conditions which limit the triple-phase region. Within this region high negative pressures are generated in the unfrozen liquid independent of the pore size where it exists. The findings are applied to water in the disperse matrix of hardened cement paste. They are the basis for "micro ice lens pumping". Copyright 2001 Academic Press. 相似文献
50.
Matthias Westerhausen Christin Birg Holger Piotrowski Tassilo Habereder Max Suter Heinrich Nth 《无机化学与普通化学杂志》2001,627(5):882-890
Formation of Alkaline Earth Metal‐Arsenic Cages via the Metalation of Triisopropylsilylarsane with Calcium, Strontium, and Barium Bis[bis(trimethylsilyl)amide] in Tetrahydrofuran The metalation of triisopropylsilylarsane with the alkaline earth metal bis[bis(trimethylsilyl)amides] in tetrahydrofuran yields the THF complexes of calcium ( 1 ), strontium ( 2 ), and barium‐bis(triisopropylsilylarsanide) ( 3 ). Dissolving of these compounds in toluene leads to the elimination of triisopropylsilylarsane and the formation of the THF complexes of tetraalkaline earth metal hexakis(triisopropylsilylarsanide)‐triisopropylsilylarsanediide of calcium ( 4 ), strontium ( 5 ), and barium ( 6 ), respectively. The central polyhedron of compound 4 can be described as two trigonal bipyramids with the metal atoms in apical positions, connected via the arsanediide substituent as a common corner. The central moieties of the compounds 5 and 6 consist of four trigonal bipyramids which are connected by common edges as well as common faces. 相似文献