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991.
Vadim A. Soloshonok Takeshi Yamada Hisanori Ueki Tanner K. Cook Anatolii V. Soloshonok Yasufumi Ohfune 《Tetrahedron》2006,62(26):6412-6419
This paper presents a practical and efficient asymmetric synthesis of enantiomerically pure 4-aminoglutamic acids using a quite unusual methylene dimerization of chiral nucleophilic glycine equivalents with dichloromethane under phase-transfer catalysis (PTC) conditions. From a synthetic standpoint, the reported procedure is highly operationally convenient and scalable as it does not require any chromatographic purification of the intermediate products. 相似文献
992.
Seiji Suga Shinkiti Suzuki Jun-ichi Yoshida 《Journal of the American Chemical Society》2002,124(1):30-31
Carbocations, carbon radicals, and carbanions are important reactive carbon intermediates in organic chemistry, and their interconversions can be carried out by redox processes. Although, such relationships have been well recognized, experimental work has been limited to analytical studies on highly stabilized intermediates. In this study such interconversions were examined using electrochemical reduction of "cation pools". Acyliminium cations, which were generated by low-temperature electrolysis of carbamates, were reduced electrochemically in the absence of radical acceptors. The homo coupling products formed effectively, suggesting that the one-electron reduction of the acyliminium cation produced the corresponding carbon-centered radical. Next, the electrochemical reduction of the acyliminium cations in the presence of electron-deficient olefins was examined. The cross coupling products were obtained in good-to-moderate yields. A mechanism involving radical addition to the double bond followed by the reduction of the resulting radical to the carbanion was suggested. The overall transformation serves as redox-mediated formal addition of C-H to C=C. The present strategy opens new opportunities to manipulate reactive carbon species using redox processes in organic synthesis. 相似文献
993.
Irinotecan or 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) is an anticancer pro-drug used in the treatment of many types of cancer. We describe here the validation of an analytical method for CPT-11 and its metabolites, including an active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), its glucuronidated form, SN-38G, and several cytochrome P450 3A-mediated products such as 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (APC) using a high-performance liquid chromatography connected to parallel fluorescence and mass spectrometry detection systems. This method is characterized as follows: (1) simple extraction of the analytes from biomaterials with perchloric acid/methanol; (2) sensitive quantitation of major metabolites (SN-38G, SN-38 and APC) with a fluorescence detector (FLD), where the limits of quantitation by FLD were 2.5 ng/mL for SN-38G and APC, 5 ng/mL for CPT-11 and 1 ng/mL for SN-38, respectively; (3) parallel selective monitoring of the metabolites including minor metabolites with a mass selected detector (MSD). There was no observed interference by other drugs expected to be co-administered. This method showed its usefulness by identifying a novel metabolite produced in human hepatic microsomes. The results indicate that this combination of FLD and MSD enables a highly selective analysis of CPT-11 and its metabolites, and is useful for studies both in vivo and in vitro. 相似文献
994.
Mitsuru Ueda Mutsumi Honda Jun-ichi Sugiyama Hiroshi Ito 《Journal of polymer science. Part A, Polymer chemistry》1993,31(4):949-955
3-Methylene-5,5′-dimethyl-2-pyrrolidinone (α-MDMP), a cyclic analog of N-substituted methacrylamide, was synthesized and polymerized with α,α′-azobis (isobutyronitrile) (AIBN) in solution. Poly(α-MDMP) is only soluble in dimethyl sulfoxide (DMSO) at room temperature. Thermogravimetry of poly(α-MDMP) showed 10% weight loss at 355°C in air and 400°C under nitrogen, respectively. The kinetics of α-MDMP homopolymerization with AIBN was investigated in DMSO. The rate of polymerization (Rp) can be expressed by Rp = k[AIBN]0.49[α-MDMP]1.0 and the overall activation energy has been calculated to be 73.2 kJ/mol. Monomer reactivity ratios in copolymerization of α-MDMP (M2) with methyl methacrylate (M1) are r1 = 0.71 and r2 = 0.71, from which Q and e values of α-MDMP are calculated as 0.75 and -0.43, respectively. © 1993 John Wiley & Sons, Inc. 相似文献
995.
Fusae Nakanishi Hachiro Nakanishi Masaki Hasegawa Yoshiji Yamada 《Journal of polymer science. Part A, Polymer chemistry》1975,13(11):2499-2506
The photochemical reaction of m-phenylene diacrylic acid dimethyl ester (m-PDA Me) crystals and solutions has been studied to clarify the effects of the molecular shape on four-center type photopolymerization of diolefins. On irradiation, m-PDA Me crystals were converted into amorphous oligomers having more than two kinds of cyclobutane rings with respect to steric configuration. The characteristic oligomer formation is explained by considering a two-step mechanism: topochemical dimer formation in an ordered crystal lattice and subsequent random cycloaddition in a disordered crystal lattice. In m-PDA Me solution, reversible cyclobutane ring formation and cis–trans isomerization take place, depending on the concentration of m-PDA Me in solution and the wavelength of the irradiating light. The multiplicity of reactivity in various states has been established. 相似文献
996.
(Z)-3-(α-Alkoxycarbonyl-α-cyanomethylene)-2-oxo-1,2,3,4-tetrahydroquinoxalines 3 and (Z)-3-(α-alkoxycarbonyl-α-cyanomethylene)-3,4-dihydrobenzo[g]quinoxalin-2(1H)-ones 5 possessing various alkoxycarbonyl groups were prepared in good yields directly from the reaction of dialkyl (E)-2,3-dicyanobutendioates 1 with o-phenylenediamine ( 2 ) or with 2,3-diaminonaphthalene ( 4 ), respectively. Furthermore, 2,3-diaminopyridine ( 6 ) and 3,4-diaminopyridine ( 7 ) were reacted with the diethyl ester 1b to give (Z)-2-(α-cyano-α-ethoxycarbonylmethylene)-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one ( 8 ) and (Z)-3-(α-cyano-α-ethoxycarbonylmethylene)-3,4-dihydro-1H-pyrido[3,4-b]pyrazin-2-one ( 9 ), respectively. The structural studies of 3, 5, 8 , and 9 were carried out by nmr experiments in some details. 相似文献
997.
Osamu Kujirai Kei Yamada Muneyuki Kohri Haruno Okochi 《Fresenius' Journal of Analytical Chemistry》1991,339(3):133-136
Summary Inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been developed for a simultaneous determination of traces of non-hydride-forming elements in high-purity Mo and molybdenum trioxide. Coprecipitation of diverse elements with lanthanum hydroxide is used to separate them from the Mo matrix and for concentration. Effects of pH and amount of La on the recoveries of diverse elements are discussed. Ten elements (Co, Cr, Cu, Fe, Mn, Ni, Ti, V, Zn, and Zr) are quantitatively recovered and determined. Matrix-matched calibration solutions are used for the determination. 相似文献
998.
Choi M Yamamoto K Itoh T Makishima M Mangelsdorf DJ Moras D DeLuca HF Yamada S 《Chemistry & biology》2003,10(3):261-270
We present a new method to investigate the details of interaction between vitamin D nuclear receptor (VDR) and various ligands, namely a two-dimensional alanine scanning mutational analysis. In this method, the transactivation of various ligands is studied in conjunction with a series of alanine scanning mutations of the residues lining the ligand binding pocket (LBP) of VDR, and the complete set of results is profiled in a patch table. We investigated examples from four structurally diverse groups of known VDR ligands: the native vitamin D hormone and two compounds with the same side chain configuration; four 20-epi compounds; three 19-nor compounds; and two nonsecosteroids. The patch table of the results indicates characteristics of each group in terms of its interaction with 18 LBP residues. We demonstrate the validity of this approach by application to docking studies of the two nonsecosteroids. 相似文献
999.
A. Yamada S. Grossman O. Vogl 《Journal of polymer science. Part A, Polymer chemistry》1980,18(6):1739-1758
A synthetic approach that makes symmetrically 2,3-dialkyl-substituted succinates and compounds prepared from 2,3-dialkyl-substituted succinates easily available has been developed. Coupling of α-bromoalkanoic esters with a zinc/copper couple produced in about 40% yield 2,3-disubstituted succinates which were reduced with LiAlH4 to 2,3-disubstituted butanediols-1,4 in nearly quantitative yields. Some 2,3-disubstituted butanediols-1,4 were cyclodehydrated under reduced pressure with KHSO4 to 3,4-disubstituted tetrahydrofurans or acetylated and the diacetyl compounds pyrolyzed at 525°C to 2,3 disubstituted butadienes-1,3. The length of the alkyl chains of the 2,3-dialkylsuccinates and consequently the 2,3-dialkylbutanediols-1,4 ranged from C2 to C16. 2,3-Disubstituted butanediols-1,4, 2,3-disubstituted butadienes-1,3, and 3,4-disubstituted tetrahydrofurans are interesting monomers for polymerization experiments. 相似文献
1000.