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排序方式: 共有343条查询结果,搜索用时 218 毫秒
211.
212.
M Dettin D Silvestri R Danesin E Cretaio G Picariello E Casarin A Sonato F Romanato M Morpurgo 《Molecules (Basel, Switzerland)》2012,17(9):11026-11045
Peptide Nucleic Acids (PNAs) linked to high molecular weight (MW) poly(ethylene oxide) (PEO) derivatives could be useful conjugates for the direct functionalisation of gold surfaces dedicated to Surface Plasmon Resonance (SPR)-based DNA sensing. However their use is hampered by the difficulty to obtain them through a convenient and economical route. In this work we compared three synthetic strategies to obtain PNA-high MW PEO conjugates composed of (a) a 15-mer PNA sequence as the probe complementary to genomic DNA of Mycobacterium tuberculosis, (b) a PEO moiety (2 or 5 KDa MW) and (c) a terminal trityl-protected thiol necessary (after acidic deprotection) for grafting to gold surfaces. The 15-mer PNA was obtained by solid-phase synthesis. Its amino terminal group was later condensed to bi-functional PEO derivatives (2 and 5 KDa MW) carrying a Trt-cysteine at one end and a carboxyl group at the other end. The reaction was carried out either in solution, using HATU or PyOxim as coupling agents, or through the solid-phase approach, with 49.6%, 100% and 5.2% yield, respectively. A differential solvent extraction strategy for product purification without the need for chromatography is described. The ability of the 5 KDa PEO conjugate to function as a probe for complementary DNA detection was demonstrated using a Grating-Coupling Surface Plasmon Resonance (GC-SPR) system. The optimized PEO conjugation and purification protocols are economical and simple enough to be reproduced also within laboratories that are not highly equipped for chemical synthesis. 相似文献
213.
The Matlab implementation of a trust-region Gauss-Newton method for bound-constrained nonlinear least-squares problems is presented.
The solver, called TRESNEI, is adequate for zero and small-residual problems and handles the solution of nonlinear systems of equalities and inequalities.
The structure and the usage of the solver are described and an extensive numerical comparison with functions from the Matlab Optimization Toolbox is carried out. 相似文献
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Margherita BarberoStefano Bazzi Silvano CadamuroLorenzo Di Bari Stefano Dughera Giovanni Ghigo Daniele PadulaSilvia Tabasso 《Tetrahedron》2011,67(32):5789-5797
We have recently reported the use, in catalytic amounts, of 1,2-benzenedisulfonimide as a safe Brønsted acid in some acid-catalyzed organic reactions. With the design of new and chiral acid organocatalysts with the structure of 1,2-benzenedisulfonimide in mind, we herein propose a synthesis of 1,2-benzenedisulfonimide derivatives bearing an aryl group in the 3-position with good overall yields. The chirality of these compounds is due to the hindered rotation of the aryl group (atropisomerism). We resolved the atropisomers of one of these compounds. 相似文献
218.
Manzo E Carbone M Mollo E Irace C Di Pascale A Li Y Ciavatta ML Cimino G Guo YW Gavagnin M 《Organic letters》2011,13(8):1897-1899
The first chemical study of an Actinocyclidae nudibranch, Actinocyclus papillatus, resulted in the isolation of (-)-actisonitrile (1), a lipid based on a 1,3-propanediol ether skeleton. The structure was established by spectroscopic methods, whereas the absolute configuration of the chiral center was determined by comparing the optical properties of natural actisonitrile with those of (+)- and (-)-synthetic enantiomers, opportunely prepared. Both (-)- and (+)-actisonitrile were tested in preliminary in vitro cytotoxicity bioassays on tumor and nontumor mammalian cells. 相似文献
219.
Eric Tan Margherita Zanini Antonio M. Echavarren 《Angewandte Chemie (International ed. in English)》2020,59(26):10470-10473
An Ir‐catalyzed C(sp3)?H alkynylation of aliphatic ketones, aldehydes, and alcohols was achieved by using the corresponding oxime derivatives and a IrIII catalyst. This general reaction is selective towards primary C(sp3)?H bonds and can be used for the late‐stage C?H alkynylation of complex molecules. 相似文献
220.
Jordan De Jesus Silva Deni Mance Margherita Pucino Mathis J. Benedikter Iris Elser Michael R. Buchmeiser Christophe Copéret 《Helvetica chimica acta》2020,103(11):e2000161
A well-defined silica-supported cationic W imido alkylidene was prepared through surface organometallic chemistry. This catalyst shows preferential activity towards α- over internal olefins, which is atypical for W-based catalysts, but consistent with the strong σ-donating ability of the NHC ancillary ligand. Complementing the studies on tungsten-based d0 metathesis catalysts, the silica-supported cationic W imido alkylidene displays the highest activity among W imido catalysts for α-olefins and shows improved selectivity for this class of olefins compared to Mo-based catalysts. 相似文献