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排序方式: 共有880条查询结果,搜索用时 296 毫秒
121.
John T. Gupton Alex Shimozono Evan Crawford Joe Ortolani Evan Clark Matt Mahoney Campbell Heese Jeffrey Noble Carlos Perez Mandry Rene Kanters Raymond N. Dominey Emma W. Goldman James A. Sikorski Daniel C. Fisher 《Tetrahedron》2018,74(21):2650-2663
Highly functionalized pyrroles with appropriate regiochemical functionality represent an important class of marine natural products and potential drug candidates. We describe herein a detailed study of the reaction of α-aminoacid esters with vinylogous amides and also β-halovinylaldehydes for the regiospecific synthesis of 2,3,4-trisubstituted and 1,2,3,4-tetrasubstituted pyrroles. Since the vinylogous amides and β-halovinylaldehydes are readily available precursors, rapid access to a wide variety of unsymmetrically substituted pyrroles is accomplished via this methodology. 相似文献
122.
A novel approach to the valuable quaternary 3-aminooxindole skeleton is reported on the basis of intramolecular arylation of enolates of substituted amino acids. The reaction tolerates dialkyl- and arylalkylamines as well as a range of carbon substituents (primary and secondary alkyl, aryl). The cyclization of N-indolyl-substituted substrates is accompanied by direct C-H arylation of the indole, leading to indolo-fused benzodiazepines. 相似文献
123.
How to confirm identified toxicants in effect-directed analysis 总被引:1,自引:0,他引:1
Brack W Schmitt-Jansen M Machala M Brix R Barceló D Schymanski E Streck G Schulze T 《Analytical and bioanalytical chemistry》2008,390(8):1959-1973
Due to the production and use of a multitude of chemicals in modern society, waters, sediments, soils and biota may be contaminated
with numerous known and unknown chemicals that may cause adverse effects on ecosystems and human health. Effect-directed analysis
(EDA), combining biotesting, fractionation and chemical analysis, helps to identify hazardous compounds in complex environmental
mixtures. Confirmation of tentatively identified toxicants will help to avoid artefacts and to establish reliable cause–effect
relationships. A tiered approach to confirmation is suggested in the present paper. The first tier focuses on the analytical
confirmation of tentatively identified structures. If straightforward confirmation with neat standards for GC–MS or LC–MS
is not available, it is suggested that a lines-of-evidence approach is used that combines spectral library information with
computer-based structure generation and prediction of retention behaviour in different chromatographic systems using quantitative
structure–retention relationships (QSRR). In the second tier, the identified toxicants need to be confirmed as being the cause
of the measured effects. Candidate components of toxic fractions may be selected based, for example, on structural alerts.
Quantitative effect confirmation is based on joint effect models. Joint effect prediction on the basis of full concentration–response
plots and careful selection of the appropriate model are suggested as a means to improve confirmation quality. Confirmation
according to the Toxicity Identification Evaluation (TIE) concept of the US EPA and novel tools of hazard identification help
to confirm the relevance of identified compounds to populations and communities under realistic exposure conditions. Promising
tools include bioavailability-directed extraction and dosing techniques, biomarker approaches and the concept of pollution-induced
community tolerance (PICT).
Figure Toxicity confirmation in EDA as a tiered approach 相似文献
124.
Aileen M. Eagleton Emma K. Ambrogi Sophia A. Miller Dr. Nataliia Vereshchuk Prof. Katherine A. Mirica 《Angewandte Chemie (International ed. in English)》2023,62(49):e202309078
Owing to high modularity and synthetic tunability, metal–organic frameworks (MOFs) on textiles are poised to contribute to the development of state-of-the-art wearable systems with multifunctional performance. While these composite materials have demonstrated promising functions in sensing, filtration, detoxification, and biomedicine, their applicability in multifunctional systems is only beginning to materialize. This review highlights the multifunctionality and versatility of MOF-integrated textile systems. It summarizes the operational goals of MOF@textile composites, encompassing sensing, filtration, detoxification, drug delivery, UV protection, and photocatalysis. Building upon these recent advances, this review concludes with an outlook on emerging opportunities for the diverse applications of MOF@textile systems in the realm of smart wearables. 相似文献
125.
Jean d’Angelo Georges Morgant Nour Eddine Ghermani Didier Desmaële Bernard Fraisse François Bonhomme Emma Dichi Mehrez Sghaier Yanling Li Yves Journaux John R.J. Sorenson 《Polyhedron》2008
Purposes of these studies were to synthesize Zn(II) and Co(II) complexes of 3-nitro-4-hydroxybenzoic acid, determine their structures through X-ray crystallography, and obtain their anticonvulsant activities. Thermogravimetric, differential scanning calorimetry, impedance of aqueous solutions and magnetic properties analyses were also determined. Anticonvulsant and related activities of these complexes as well as Zn(II), Co(II), Ni(II) and Mg(II) (5-nitrosalicylato) complexes were determined by the National Institutes of Health, Antiepileptic Development Program. Results of these analyses are presented to document unique bonding features and physical properties of these compounds and their anticonvulsant activities. It is concluded that these compounds have chemical and physical properties that can be used to account for their anticonvulsant activities. 相似文献
126.
Aberg C Wennerström H Sparr E 《Langmuir : the ACS journal of surfaces and colloids》2008,24(15):8061-8070
The "acidic mantle" of the skin surface has been related to several essential functions of the skin, although the origin of the acidity is still obscure. In this paper, we investigate how different transport processes can influence the local proton concentration inside a membrane consisting of oriented lipid bilayers. This system is chosen as a simple model of the extracellular lipids in the upper layer of the skin, the stratum corneum. We present a theoretical model for diffusional transport over the membrane in the presence of an osmotic gradient and a gradient in CO(2), taking into account the influence of these gradients on the lipid structure and the local electrostatics. We are also discussing the complications in applying the concept of pH to the stratum corneum. From this, we make the following conclusions: (i) The definition of pH in the stratum corneum is ambiguous, and thus, all statements regarding pH should always be related to a clear definition. (ii) A natural definition of pH in the stratum corneum can be proposed which takes into account local heterogeneity, local charges, and the fact that the stratum corneum is not in thermodynamical equilibrium. (iii) Diffusive transport across an oriented bilayer stack in the presence of an osmotic gradient and/or a gradient in CO(2) can give rise to a substantial gradient in pH. (iv) The results from the simplified model can be correlated to experimental observations of pH in the stratum corneum. 相似文献
127.
Jarvis RM Johnson HE Olembe E Panneerselvam A Malik MA Afzaal M O'Brien P Goodacre R 《The Analyst》2008,133(10):1449-1452
There is a need for a method to facilitate the development of novel, reproducible colloidal surface-enhanced Raman scattering (SERS) substrates to encourage the use of SERS in applied studies. In this study we show for the first time that by using suitably designed SERS experiments in conjunction with multivariate analysis of variance (MANOVA), an objective assessment of colloidal SERS reproducibility can be made. This is demonstrated with the analyte cresyl violet, but could be extended to any analyte of interest for which reproducible SERS data are needed. 相似文献
128.
Bio-electrospraying, a non-contact jet-based direct cell engineering approach, was recently pioneered and demonstrated for handling a wide range of primary living cells. In those studies, post-treated cells were biologically assessed in comparison to several controls by way of flow cytometry. Although flow cytometry accurately assesses those viable populations of cells, subtle effects at a sub-cellular level could have been missed. Therefore, in the present study we demonstrate metaphase chromosome breakage studies carried out on single-needle bio-electrosprayed human T-lymphocytes, which are compared with several controls. The results indicate that post-treated T-lymphocytes do not demonstrate any increase in chromosome damage in comparison to control cells. These studies further validate bio-electrospraying as a technique with potential for clinical utility. 相似文献
129.
130.
Liana Hie Emma L. Baker Sarah M. Anthony Dr. Jean‐Nicolas Desrosiers Dr. Chris Senanayake Prof. Dr. Neil K. Garg 《Angewandte Chemie (International ed. in English)》2016,55(48):15129-15132
Recent studies have demonstrated that amides can be used in nickel‐catalyzed reactions that lead to cleavage of the amide C?N bond, with formation of a C?C or C?heteroatom bond. However, the general scope of these methodologies has been restricted to amides where the carbonyl is directly attached to an arene or heteroarene. We now report the nickel‐catalyzed esterification of amides derived from aliphatic carboxylic acids. The transformation requires only a slight excess of the alcohol nucleophile and is tolerant of heterocycles, substrates with epimerizable stereocenters, and sterically congested coupling partners. Moreover, a series of amide competition experiments establish selectivity principles that will aid future synthetic design. These studies overcome a critical limitation of current Ni‐catalyzed amide couplings and are expected to further stimulate the use of amides as synthetic building blocks in C?N bond cleavage processes. 相似文献