primary amines from carboxylic acids through a Lossen rearrangement of hydroxamicacid derivatives, which were in situ generated by the reaction of carboxylic acids with O-trimethylsilylhydroxylamine (NH2OTMS) and carbonyl diimidazole (CDI, 1.5 equiv) in dimethyl sulfoxide at room temperature, has been achieved. This one-pot method could be applied to various carboxylic acids such as aromatic, heteroaromatic
Thioether-Directed NiH-Catalyzed Remote γ-C(sp<sup>3</sup>)–H Hydroamidation of Alkenes by 1,4,2-Dioxazol-5-ones
作者:Bingnan Du、Yuxin Ouyang、Qishu Chen、Wing-Yiu Yu
DOI:10.1021/jacs.1c05834
日期:2021.9.22
amidation of unactivated alkenes. Due to the preference for five-membered nickelacycle formation, the chain-walking isomerization initiated by the NiH insertion to an alkene can be terminated at the γ-methylene site remote from the alkene moiety. By employing 2,9-dibutyl-1,10-phenanthroline (L4) as the ligand and dioxazolones as the reagent, the amidation occurs at the γ-C(sp3)–H bonds to afford the amide
Redox-active cytotoxic diorganotin(IV) cycloalkylhydroxamate complexes with different ring sizes: Reduction behaviour and theoretical interpretation
作者:Xianmei Shang、Elisabete C.B.A. Alegria、M. Fátima C. Guedes da Silva、Maxim L. Kuznetsov、Qingshan Li、Armando J.L. Pombeiro
DOI:10.1016/j.jinorgbio.2012.08.019
日期:2012.12
Two series of new diorganotin(IV) cycloalkylhydroxamate complexes with different ring sizes (cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl), formulated as the mononuclear [R2Sn(HL)(2)] (1:2) (a, R=Bu-n and Ph) and the polymeric [R2SnL](n) (1:1) (b, R=Bu-n) compounds, were prepared and fully characterized. Single crystal X-ray diffraction for [(Bu2Sn)-Bu-nC5H9C(O)NHO}(2)] (3a) discloses the cis geometry and strong intermolecular NH center dot center dot center dot O interactions. The in vitro cytotoxic activities of the complexes were evaluated against HL-60, Bel-7402, BGC-823 and KB human tumour cell lines, the greater activity concerning [(Bu2Sn)-Bu-n(HL)(2)] [HL=C3H5C(O)NHO (1a), C6H11C(O)NHO (4a)] towards BGC-823. The complexes undergo, by cyclic voltammetry and controlled-potential electrolysis, one irreversible overall two-electron cathodic process at a reduction potential that does not appear to correlate with the antitumour activity. The electrochemical behaviour of [R2Sn(C5H9C(O)NHO)(2)] [R=Bu-n (3a), Ph (7a)] was also investigated using density functional theory (DFT) methods, showing that the ultimate complex structure and the mechanism of its formation are R dependent: for the aromatic (R = Ph) complex, the initial reduction step is centred on the phenyl ligands and at the metal, being followed by a second reduction with Sn-O and Sn-C ruptures, whereas for the alkyl (R=Bu-n) complex the first reduction step is centred on one of the hydroxamate ligands and is followed by a second reduction with Sn-O bond cleavages and preservation of the alkyl ligands. In both cases, the final complexes are highly coordinative unsaturated Sn-II species with the cis geometry, features that can be of biological significance. (C) 2012 Elsevier Inc. All rights reserved.
Ethylene biosynthesis. 12. Analog approach to the active site topography of the ethylene-forming enzyme. Novel hydroxamate inhibitors
作者:Michael C. Pirrung、Jun Cao、Jrlung Chen
DOI:10.1021/jo00123a012
日期:1995.9
In order to understand both the substrate specificity and active site topography of the ethylene-forming enzyme (EFE), a number of analogs of its substrate, 1-aminocyclopropanecarboxylic acid, have been prepared and studied as inhibitors. Because of the dependence of EFE activity on iron, hydroxamic acids, a functional group known to bind iron tightly, derived from several small carboxylic/amino acids were studied along with the parent amino acids. The activity of these materials was assayed in vitro against the purified EFE from apple fruit. The varying potency of the amino acid hydroxamates suggests that they do not act simply by binding to iron and removing it from the enzyme. The order of their potency was consistent with the idea that binding reflects both metal chelation and hydrophobic interactions in the active site. The most potent inhibitor, ACC-hydroxamate, has about 1 mu M K-i.