共查询到20条相似文献,搜索用时 0 毫秒
1.
Toshio Shinbo Tomohiko Yamaguchi Koichiro Nishimura Masayoshi Kikkawa Masaaki Sugiura 《Analytica chimica acta》1987
Polymeric membrane electrodes based on the chiral crown ether, 2,3:4,5-bis-[1,2-(3-phenylnaphtho)]-1,6,9,12,15,18-hexaoxacycloeicosa-2,4-diene, were prepared, and their characteristics were examined. The electrodes showed good enantiomer-selectivity for many amino acid methylesters, the enantiomer-selective factor reaching the high value of 13 for phenylglycine methyl ester. The electrodes responded preferably to the enantiomer forming the more stable complex with the crown ether. The electrodes proved useful for determining the concentrations of each enantiomer. The calculated concentrations from the potential changes of the electrodes were in good agreement with the predicted ones. 相似文献
2.
A convenient synthetic method was reported for the preparation of N-phthaloyl dehydroamino acid esters from easily accessible vinyl bromides (or vinyl tosylate) and potassium phthalimide. Rh-catalyzed asymmetric hydrogenation of these substrates with TangPhos gave the products with good to excellent enantioselectivities (up to 99% ee). 相似文献
3.
O-Alkyl thioesters may be prepared from the corresponding carboxylic esters by successive treatment with lithium diisopropylamide, chlorotrimethylsilane, and hydrogen sulfide. 相似文献
4.
5.
B. A. Trofimov L. N. Sobenina A. I. Mikhaleva 《Chemistry of Heterocyclic Compounds》1991,27(7):801-701
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 996–997, July, 1991. 相似文献
6.
John B. Paine 《Journal of heterocyclic chemistry》1987,24(2):351-355
A convenient synthesis of alkyl-substituted ethyl nicotinates 8 was devised, using 3-cyano-2(1H)-pyridones 4. These were converted to the corresponding 2-bromo-3-cyanopyridines 5 with boiling phosphorus tribromide. The resulting 5 were smoothly debrominated to 3-cyanopyridines 6 with zinc dust in boiling ethanolic acetic acid. The nitrile function was hydrolyzed in boiling 6N hydrochloric acid, and the resulting nicotinic acid hydrochlorides 7 esterified with refluxing triethyl orthoformate, to give the ethyl nicotinates 8. A modified formylation of 2-butanone led to the sodium salt of 2-methyl-3-oxobutanal ( 3a ) of enhanced purity. 相似文献
7.
8.
Rowe GE Aomari H Chevaldina T Lafrance M St-Arnaud S 《Journal of chromatography. A》2008,1177(2):243-253
Thermodynamic analysis of hydrophobic interaction chromatography of amino acid methyl esters showed entropy-driven adsorption, consistent with solvophobic theory, except for phenyl ester on the Toyopearl resins. All esters adsorbed more strongly to the Toyopearl resins, including the polymethacrylate base matrix, than to Butyl Sepharose. Enthalpy changes were more favorable with the former, explaining the retention difference between Toyopearl Butyl and Butyl Sepharose. An enthalpy change versus heat capacity change plot showed Van der Waals interactions predominantly with the resin matrix. Literature data revealed the same effect for dansylamino acids, shown by isothermodynamic temperature analysis to adsorb more entropically than the esters. 相似文献
9.
V. M. Tormyshev T. V. Mikhalina O. Yu. Rogozhnikova T. I. Troitskaya D. V. Trukhin 《Russian Journal of Organic Chemistry》2006,42(7):1031-1035
Reaction of ethyl isocyanoacetic acid with sodium hydride in anhydrous benzene, followed by treatment with carboxylic acid chlorides or N-(acyloxy)pyrrolidine-2,5-diones, gives 5-substituted oxazole-4-carboxylic acid esters. The procedure is applicable to derivatives of various carboxylic acids, including saturated aliphatic, α,β-unsaturated, alicyclic, aromatic, heterocyclic, and N-Boc-protected amino acids. 相似文献
10.
Reaction of ADP with amino acid methyl esters mediated by trimethylsilyl chloride in pyridine produced adenosine 5'-phosphoramidates in good yields under mild conditions, it is interesting that nucleophilic attack of amino acid methyl esters only occurred on alpha-phosphorus of ADP. 相似文献
11.
12.
Hari Narayan Pati Saswata Lahiri Ramesh Kumar Sabbam Vijaya Bhaskar Vangala Boobalan Ramalingam Salmara Ganeshbhat Hiriyanna Prosenjit Bose 《Journal of heterocyclic chemistry》2008,45(3):917-920
Synthesis of Olmesartan medoxomil methyl ether ( 2 ), a potential impurity of Olmesartan medoxomil ( 1 ), an angiotensin II receptor blockers is reported for the first time. 相似文献
13.
A multigram scale synthesis of the four stereoisomers of methyl 3-silylglycidates (epoxysilanes) with high enantiopurity is described. Key reactions include a Sharpless asymmetric epoxidation (SAE) of a trans-vinylsilane and an enzymatic resolution of a racemic cis-epoxysilane to establish the desired configurations. Few chromatographic separations (5 columns out of 13 steps) are required for purification, establishing a convenient reaction sequence for both the trans- and cis-isomers. 相似文献
14.
15.
An efficient and convenient synthesis of the title compond 1 is described. The approach to the synthesis is based on hydride reduction of the 4-methoxypyridinium salt 5 , followed by acid hydrolysis of the resulting vinyl ether intermediate 6 . 相似文献
16.
A practical method for the quantitative determination of protein amino acids by gas-liquid chromatography (GLC) is described. All of the common protein amino acids except arginine can be readily converted into their N-isobutyloxycarbonyl (N-isoBOC) methyl ester derivatives by a simple procedure involving isobutyloxycarbonylation with isobutyl chloroformate in aqueous medium, followed by methylation with diazomethane. Arginine was converted into N-isoBOC ornithine methyl ester by treatment with arginase, followed by the above derivatization procedure. The resulting N-isoBOC methyl esters of the amino acids have good GLC properties. Complete resolution of the derivatives of 20 protein amino acids was achieved by using a dual-column system consisting of a 0.65% Poly-A-101A column and a 0.70% FFAP-Poly-A-101A (1:1, w/w) column. The reproducibility of response was found to be good for derivatives carried through the entire chemical and chromatographic procedure. The calibration graphs were linear and showed no statistical bias. The results of recovery experiments with synthetic mixtures containing known amounts of the amino acids were satisfactory, the recoveries ranging from 94.3 to 106.2%. 相似文献
17.
Ilaria Paolini Maria de la Cruz Pozo-Carrero Francesca Barbetti Zbigniew J. Kaminski Anna M. Papini 《Tetrahedron letters》2007,48(16):2901-2904
Optimization of coupling reactions of glycosylamines with Fmoc-protected aspartic acid, by microwave approach, is described. Different reaction conditions, quantities of substrates and solvents were tested to develop simple and reproducible methodologies. The best results were obtained using new triazine-based coupling reagents with a monomode microwave Discover® BenchMate™ instrument (CEM). The N-glycosyl amino acids were then deprotected to achieve final products for SPPS. 相似文献
18.
Hiroyuki Ota 《Tetrahedron letters》2004,45(20):3903-3907
Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from cyclic ketones and chloromethyl p-tolyl sulfoxide in three steps in good yields, with N-lithio arylamines gave sulfinylaziridines in high yields. On treatment with N-lithio aniline or N-lithio p-chloroaniline, the sulfinylaziridines gave α-amino aldehydes in high yields. The α-amino aldehydes were converted to amino alcohols and α-amino acid methyl esters in moderate to good yields. This procedure offers an efficient method for synthesis of cyclic α-quaternary α-amino aldehydes, amino alcohols, and α-amino acid derivatives from cyclic ketones. 相似文献
19.
A synthesis of aziridine esters based on the cyclisation of amino selanyl esters induced by the selanyl group activation was developed with either the Meerwein salt or NBS. Two asymmetric approaches are proposed: the diastereoselective reductions of α-selanyl β-iminoesters derived from α-oxoesters, which lead to cis chiral aziridine esters 6 and 6′; and the diastereoselective conjugate additions of a chiral amide to α,β-unsaturated esters providing trans chiral aziridine esters 6 and 6″. 相似文献
20.
[reaction: see text] The facile, two-pot synthesis of N-methyl amino acid esters by way of reductive amination is presented. Side chain protection schemes are not required, the starting materials are all commercially available, and the synthetic method is straightforward and affords desired product in very high yield. 相似文献