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1.
The synthesis of anhydronectriachrysone (2) through the DIBAH reduction of toralactone (3), followed by dehydration of the corresponding lactol (4) is reported (38% yield). 相似文献
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Wiktor Szymanski 《Tetrahedron》2008,64(14):3197-3203
An efficient, chemoenzymatic method for the multicomponent synthesis of unnatural tripeptides is presented. Development of a previously described procedure combines the diversity offered by multicomponent reactions with the selectivity of biocatalysts and allows the convenient introduction of varied amino acid moieties into the tripeptide scaffold, with control of the stereochemistry. Additionally, it allows the introduction of a methyl group to the amide nitrogen, leading to derivatives of N-methylated amino acids. 相似文献
4.
Emilio Scamporrino Placido Mineo Sandro Dattilo Daniele Vitalini Emanuela Spina 《Macromolecular rapid communications》2007,28(15):1546-1552
Some new water‐soluble bis‐porphyrins, constituted of two porphyrin units spaced by means of aliphatic bridges of different lengths, were synthesized and characterized by MALDI‐TOF mass spectrometry, 1H NMR and UV‐vis spectroscopy. The hydrosolubility of these uncharged compounds was guaranteed from the presence of six long PEG chains bound on the peripheral positions of the two porphyrins. Cobalt and zinc derivatives were also prepared. In the case of Co‐bis‐porphyrin, the appearance of induced circular dichroism (ICD) signals in water solution confirmed the formation of stable complexes with some amino acids, in which the bis‐porphyrin behaves like molecular tweezers.
5.
《Analytical letters》2012,45(13):2189-2206
Abstract In the study of voltammetric electronic tongues, a key point is the preprocessing of the departure information, the voltammograms which form the response of the sensor array, prior to classification or modeling with advanced chemometric tools. This work demonstrates the use of the discrete wavelet transform (DWT) for compacting these voltammograms prior to modeling. After compression, a system based on artificial neural networks (ANNs) was used for the quantification of the electroactive substances present, using the obtained wavelet decomposition coefficients as their inputs. The Daubechies wavelet of fourth order permitted an effective compression up to 16 coefficients, reducing the original dimension by ca. 10 times. The case studied is a mixture of three oxidizable amino acids:tryptophan, cysteine, and tyrosine. With the reduced information, one ANN per specie was trained using the Bayesian regularization algorithm. The proposed procedure was compared with the more conventional treatments of downsampling the voltammogram, or its feature extraction employing principal component analysis prior to ANNs. 相似文献
6.
从α-L-氨基酸酯在摩尔级高产率制备了光学纯N-(O,S-二甲基硫代磷酰基)α-L-氨基酸酯. 利用IR,1H-NMR,摩尔旋光鉴定了结构特征,利用生物测试法研究了杀虫活性.4 种活性氨基酸杀虫剂在0.01% ~0.001% 浓度内,它们对两令棉铃虫的触杀死亡率为100% ~80% ,胃杀死亡率为95% ~50% ,而且杀虫活性有随活性氨基酸杀虫剂分子中R-基团碳链增长而增强的趋势. 相似文献
7.
Organosilicon derivatives of glycine, - and -alanine, and -methylalanine were prepared by the reaction of methyl esters of - and -halocarboxylic acids withN-methylaminomethyltriethoxysilane in the presence of triethylamine. The compounds synthesized were converted into the correspondingN-silatran-l-ylmethyl derivatives. Trimethylsilyliodoacetate reacts withN-methylaminomethyltrietoxysilane to give 2,2-diethoxy4-methyl-1-oxa-4-aza-2-silacyclohexane-6-one. Its reaction with triethanolamine leads toN-methyl-N-(silatran-l-ylmethyl)glycine.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 341–343, February, 1995. 相似文献
8.
Yu. I. Smolin A. E. Lapshin G. A. Pankova Yu. N. Osipova 《Journal of Structural Chemistry》2004,45(2):327-330
Crystals of [(C3NO2H7)2H2SO4] composition were analyzed by single-crystal X-ray diffraction (triclinic, P
, a = 7.431(3), b = 9.826(3), c = 10.081(3) , = 120.07(5), = 104.73(5), = 94.24(5)°). The independent part of the unit cell contains two alanine molecules and one sulfate ion. The amino group is additionally protonated in both molecules. One of the alanine molecules forms a hydrogen bond to the symmetry-related molecule to yield a DL-pair, while the other alanine molecule is hydrogen-bonded to the sulfate ion only. 相似文献
9.
Kinetics of oxidative decarboxylation of arginine, glutamine, histidine and lysine by bromamine-T (BAT) was investigated in
acid and alkaline media at 30° and 20° fespectively. The form of the rate law at low concentrations of HClO4 has been worked out. Proton inventory studies in H2O-D2O mixtures with Arg as a probe have been made. The rate increases in the order: His > Lys > Arg > Glu - NH2. In alkaline media, the rate shows a first order dependence on [BAT]0 and is fractional in [S] and [OH].p-Toluene sulphonamide retards the rate. Mechanisms proposed are consistent with the experimental rate laws. 相似文献
10.
The crystals of [Co6H2O][Co4H2O2Gly]2SO4 were studied by X-ray diffraction analysis (triclinic, P
, a = 5.975(5), b = 15.469(5), c = 6.765(5) , =120.71(5), =83.23(5), =98.77(5)°). The structure contains complex cations of two types: [Co6H2O]2+ and [Co4H2O2Gly]2+ and SO
4
2–
anions linked by hydrogen bonds and electrostatic forces. Three chemically nonequivalent charged layers can be distinguished in the structure: one layer is formed by cobalt hexaaqua complexes, another by [Co4H2O2Gly]2– complexes, and the third layer consists of sulfate anions interlaying the former two. The layers alternate along the b axis and are connected by a 3D system of hydrogen bonds. 相似文献