排序方式: 共有32条查询结果,搜索用时 15 毫秒
11.
12.
van Zutphen S Pantoja E Soriano R Soro C Tooke DM Spek AL den Dulk H Brouwer J Reedijk J 《Dalton transactions (Cambridge, England : 2003)》2006,(8):1020-1023
New asymmetric trans-platinum(II) complexes, composed of an isopropylamine, an azole and two carboxylate leaving groups, are presented. The crystal and molecular structures of one of the complexes has been determined and the cytotoxicity and reactivity with 5'-guanosine monophosphate is reported. The complexes show a reduced reactivity, but no decrease in cytotoxic activity compared to their chloro-counterparts. Furthermore the complexes largely overcome cisplatin resistance, they therefore present an interesting class of antitumour active trans-platinum complexes. 相似文献
13.
Kuil M Goudriaan PE Kleij AW Tooke DM Spek AL van Leeuwen PW Reek JN 《Dalton transactions (Cambridge, England : 2003)》2007,(22):2311-2320
The template-induced formation of chelating bidentate ligands by the selective self-assembly of two monodentate pyridyl phosphorus ligands on a rigid bis-zinc(II) salphen template with two identical binding sites was studied. Using UV-vis, NMR-spectroscopy and X-ray analysis the formed structures were unambiguously proven. The application of these templated bidentate ligands in transition metal catalysis showed, in most cases, typical bidentate character. Compared to previous work based on a more flexible bis-zinc(II) porphyrin template, the current catalytic data suggest that the rigidity of the template is not an important factor for the improvement of the regio- and enantioselectivity under the applied reaction conditions. 相似文献
14.
Mark Kuil IrisM. Puijk ArjanW. Kleij DuncanM. Tooke AnthonyL. Spek Joost N.H. Reek 《化学:亚洲杂志》2009,4(1):50-57
We report the assembly of supramolecular boxes and coordination polymers based on a rigid bis‐zinc(II)‐salphen complex and various ditopic nitrogen ligands. The use of the bis‐zinc(II)‐salphen building block in combination with small ditopic nitrogen ligands gave organic coordination polymers both in solution as well as in the solid state. Molecular modeling shows that supramolecular boxes with small internal cavities can be formed. However, the inability to accommodate solvent molecules (such as toluene) in these cavities explains why coordination polymers are prevailing over well‐defined boxes, as it would lead to an energetically unfavorable vacuum. In contrast, for relatively longer ditopic nitrogen ligands, we observed the selective formation of supramolecular box assemblies in all cases studied. The approach can be easily extended to chiral analogues by using chiral ditopic nitrogen ligands. 相似文献
15.
A New Mechanism for β‐Lactamases: Class D Enzymes Degrade 1β‐Methyl Carbapenems through Lactone Formation
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Christopher T. Lohans Emma van Groesen Kiran Kumar Catherine L. Tooke Dr. James Spencer Prof. Dr. Robert S. Paton Dr. Jürgen Brem Prof. Dr. Christopher J. Schofield 《Angewandte Chemie (International ed. in English)》2018,57(5):1282-1285
β‐Lactamases threaten the clinical use of carbapenems, which are considered antibiotics of last resort. The classical mechanism of serine carbapenemase catalysis proceeds through hydrolysis of an acyl‐enzyme intermediate. We show that class D β‐lactamases also degrade clinically used 1β‐methyl‐substituted carbapenems through the unprecedented formation of a carbapenem‐derived β‐lactone. β‐Lactone formation results from nucleophilic attack of the carbapenem hydroxyethyl side chain on the ester carbonyl of the acyl‐enzyme intermediate. The carbapenem‐derived lactone products inhibit both serine β‐lactamases (particularly class D) and metallo‐β‐lactamases. These results define a new mechanism for the class D carbapenemases, in which a hydrolytic water molecule is not required. 相似文献
16.
Some microwave measurements performed on a film of YIG and described recently in this journal by Borghese et al. have been examined. It is shown that, for the parallel-field case, quantitative agreement can be obtained between most of the observed lines and the results of calculations based on that theory of Damon and Eshbach. It is also suggested that, for such films of YIG, 4πM0 is about 1800 G, which is significantly higher than for the bulk material. 相似文献
17.
18.
19.
The tris(para-pyridyl)phosphine template (1) has been used in conjunction with a series of meso-substituted Zn(II)-tetraphenylporphyrins complexes (2-10) to create supramolecular encapsulated ligand assemblies via Zn-N(pyr) interactions. The structural features of supramolecular ligand 1.[2](3) have been investigated in detail using X-ray crystallography, NMR specroscopy, and UV-vis spectroscopy. The pyridylphosphine-porphyrin stoichiometry determined in solution (1:3) differs markedly with that observed in the solid state (2:5, for assembly [1](2).[2](5)). The difference originates from an unusual coordination behavior of one of the Zn centers, which is octahedrally surrounded through double axial coordination by the pyridyl groups of the two different molecules of 1. 相似文献
20.
Boldron C Ozalp-Yaman S Gamez P Tooke DM Spek AL Reedijk J 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3535-3541
A copper(II) neocuproine system has been developed for the efficient and very selective 1,6-addition of a nucleophile to the para-methyl group of 2,4,6-trimethylphenol. Crystallographic and spectroscopic data point towards the involvement of a micro-methoxo-micro-phenoxo-bridged copper species which appears to generate a highly reactive quinone methide intermediate that can be attacked by a nucleophilic reagent. 相似文献