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551.
LiAlH4‐Induced Selective Ring Rearrangement of 2‐(2‐Cyanoethyl)aziridines toward 2‐(Aminomethyl)pyrrolidines and 3‐Aminopiperidines as Eligible Heterocyclic Building Blocks
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Jeroen Dolfen Dr. Karel Vervisch Prof. Dr. Norbert De Kimpe Prof. Dr. Matthias D'hooghe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4945-4951
2‐(2‐Cyanoethyl)aziridines and 2‐aryl‐3‐(2‐cyanoethyl)aziridines were deployed as substrates for an In(OTf)3‐mediated regio‐ and stereoselective ring rearrangement upon treatment with LiAlH4, affording a variety of novel 2‐(aminomethyl)pyrrolidines and 3‐aminopiperidines, respectively. Further synthetic elaboration of the obtained 3‐aminopiperidines resulted in the formation of a peculiar and unexplored conformationally constrained imidazolidinone and diketopiperazine scaffold. 相似文献
552.
Xiaoying Xu Stephan M. Rummelt Flavien L. Morel Dr. Marco Ranocchiari Prof. Dr. Jeroen A. van Bokhoven 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15467-15472
Steric hindrance by a metal–organic framework (MOF) is shown to influence the outcome of a catalytic reaction by controlling the orientation of its intermediates. This is demonstrated using an organocatalyst, phosphine MOF LSK‐3, which is evaluated with the aid of molecular modeling and NMR spectroscopy techniques. This report is the first application of phosphine MOFs in organocatalysis and explores the potential of a framework steric hindrance to impose selectivity on a catalytic reaction. These findings expand the opportunities for control and design of the active site in the pocket of heterogeneous catalysts. 相似文献
553.
In this article we show that non-singular quadrics and non-singular Hermitian varieties are completely characterized by their
intersection numbers with respect to hyperplanes and spaces of codimension 2. This strongly generalizes a result by Ferri
and Tallini [5] and also provides necessary and sufficient conditions for quasi-quadrics (respectively their Hermitian analogues)
to be non-singular quadrics (respectively Hermitian varieties). 相似文献
554.
Back Cover: The Critical Role Played by the Catalytic Moiety in the Early‐Time Photodynamics of Hydrogen‐Generating Bimetallic Photocatalysts (ChemPhysChem 17/2016)
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555.
David Falck Nils Helge Schebb Setyo Prihatiningtyas Jiawen Zhang Ferry Heus Christophe Morisseau Jeroen Kool Bruce D. Hammock Wilfried M. A. Niessen 《Chromatographia》2013,76(1-2):13-21
In this study, an end-point-based fluorescence assay for soluble epoxide hydrolase (sEH) was transformed into an on-line continuous-flow format. The on-line biochemical detection system (BCD) was coupled on-line to liquid chromatography (LC) to allow mixture analysis. The on-line BCD was based on a flow system wherein sEH activity was detected by competition of analytes with the substrate hydrolysis. The reaction product was measured by fluorescence detection. In parallel to the BCD data, UV and MS data were obtained through post-column splitting of the LC effluent. The buffer system and reagent concentrations were optimized resulting in a stable on-line BCD with a good assay window and good sensitivity (S/N > 60). The potency of known sEH inhibitors (sEHis) obtained by LC–BCD correlates well with published values. The LC–BCD system was applied to test how oxidative microsomal metabolism affects the potency of three sEHis. After incubation with pig liver microsomes, several metabolites of sEHis were characterized by MS, while their individual potencies were measured by BCD. For all compounds tested, active metabolites were observed. The developed method allows for the first time the detection of sEHis in mixtures providing new opportunities in the development of drug candidates. 相似文献
556.
Vitaly L. Sushkevich Ren Verel Jeroen A. van Bokhoven 《Angewandte Chemie (International ed. in English)》2020,59(2):910-918
The reaction of methane with copper‐exchanged mordenite with two different Si/Al ratios was studied by means of in situ NMR and infrared spectroscopies. The detection of NMR signals was shown to be possible with high sensitivity and resolution, despite the presence of a considerable number of paramagnetic CuII species. Several types of surface‐bonded compounds were found after reaction, namely molecular methanol, methoxy species, dimethyl ether, mono‐ and bidentate formates, CuI monocarbonyl as well as carbon monoxide and dioxide, which were present in the gas phase. The relative fractions of these species are strongly influenced by the reaction temperature and the structure of the copper sites and is governed by the Si/Al ratio. While methoxy species bonded to Brønsted acid sites, dimethyl ether and bidentate formate species are the main products over copper‐exchange mordenite with a Si/Al ratio of 6; molecular methanol and monodentate formate species were observed mainly over the material with a Si/Al ratio of 46. These observations are important for understanding the methane partial oxidation mechanism and for the rational design of the active materials for this reaction. 相似文献
557.
Zhiya Dang Agnieszka Banas Sara Azimi Jiao Song Mark Breese Yong Yao Shuvan Prashant Turaga Gonzalo Recio-Sánchez Andrew Bettiol Jeroen Van Kan 《Applied Physics A: Materials Science & Processing》2013,112(3):517-523
A 3D silicon micromachining method based on proton beam writing combined with electrochemical anodization of p-type silicon enables fabrication of mid-infrared photonic crystals made of silicon and porous silicon. Here, example structures of silicon 1D and 2D photonic crystals are demonstrated. Progress and problems of fabricating 3D photonic crystals made of silicon are discussed. The strategy of fabricating photonic crystals purely made of porous silicon, and the characterization method of all these mid-infrared structures, are discussed. Due to the flexibility of this fabrication method, photonic devices and integrated photonic circuits may be built on a single chip, for which two 2D silicon photonic crystals with one on top of the other are demonstrated. 相似文献
558.
Delphine Lannuzel Jeroen de Jong Anne Trevena Jean-Louis Tison 《Analytica chimica acta》2006,556(2):476-483
A trace metal clean method for sampling and analysis of iron is set up and applied to sea ice and its associated snow, brine, and underlying seawater sampled during the Antarctic expedition “ARISE in the East” (Antarctic Remote Ice Sensing Experiment, AA03-V1, September-October 2003, 64-65°S/112-119°E, RV Aurora Australis). For clean sampling, a non-contaminating electropolished stainless steel ice corer is designed in conjunction with a polyethylene lathe equipped with Ti chisels to remove possibly contaminated outer layers of ice cores. A portable peristaltic pump with clean tubing is used on the ice to sample the underlying seawater (interface ice-water = 0, 1 and 30 m) and sea ice brine from access holes. Considering the extreme range of salinities (1-100) and Fe concentrations (0.1-100 nM) previously observed in similar environments, it is of paramount importance to set up a simple and sensitive Fe analyser adapted to such gradients. We use a flow injection analysis (FIA) technique and successfully demonstrate its capability to measure Fe concentrations directly in the sample without an on-line preconcentration/matrix separation step. We test the sensitivity, accuracy, precision and long-term stability of the analytical procedure. Also we explore and remediate interferences from a suite of other trace elements, such as Ni, Cd, Cr, Mn, Cu, Zn and Co. Analysis of reference materials NASS-5 and CASS-3 gives a good agreement with the certified values. Repeated measurements over a period of 5 months of an “in-house” Antarctic seawater standard yields a concentration of 1.02 ± 0.07 nM (n = 17, 1σ). The detection limit (3σ of the blank) is on average 0.12 nM. We report here results of the Fe distribution in sea ice that are in good agreement with previously published data. To our knowledge, this work provides the first complete profiles of total dissolvable and dissolved Fe in sea ice. 相似文献
559.
Discovery of a Mosaic‐Like Biosynthetic Assembly Line with a Decarboxylative Off‐Loading Mechanism through a Combination of Genome Mining and Imaging
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Lena Barra Marcel Kaiser Prof. Pieter C. Dorrestein Prof. Jeroen S. Dickschat Dr. Till F. Schäberle 《Angewandte Chemie (International ed. in English)》2016,55(43):13611-13614
The biosynthetic gene cluster for the antiplasmodial natural product siphonazole was identified by using a combination of genome mining, imaging, and expression studies in the natural producer Herpetosiphon sp. B060. The siphonazole backbone is assembled from an unusual starter unit from the shikimate pathway that is extended by the action of polyketide synthases and non‐ribosomal peptide synthetases with unusual domain structures, including several split modules and a large number of duplicated domains and domains predicted to be inactive. Product release proceeds through decarboxylation and dehydration independent of the thioesterase SphJ and yields the diene terminus of siphonazole. High variation in terms of codon‐usage within the gene cluster, together with the dislocated domain organization, suggest a recent emergence in evolutionary terms. 相似文献
560.
Dr. Patrick Rabe Jan Rinkel Britta Nubbemeyer Dr. Tobias G. Köllner Prof. Dr. Feng Chen Prof. Dr. Jeroen S. Dickschat 《Angewandte Chemie (International ed. in English)》2016,55(49):15420-15423
Genome sequences of social amoebae reveal the presence of terpene cyclases (TCs) in these organisms. Two TCs from Dictyostelium discoideum converted farnesyl diphosphate into (2S,3R,6S,9S)‐(?)‐protoillud‐7‐ene and (3S)‐(+)‐asterisca‐2(9),6‐diene. The enzyme mechanisms and EI‐MS fragmentations of the products were studied by labeling experiments. 相似文献