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11.
Alves GA Amato S Anjos JC Appel JA Bracker SB Cremaldi LM Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Kaplan D Karchin PE Kwan S Leedom I Lueking LH Luste GJ Mantsch PM de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Rafatian A dos Reis AC Reucroft S Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wu Z 《Physical review letters》1993,70(6):722-725
12.
[reaction: see text] A simple, efficient, and high-yielding synthesis of quinazolin-4-ylamine and thieno[3,2-d]pyrimidin-4-ylamine derivatives is reported under microwave irradiation conditions. Reaction conditions including temperature, solvent, and reaction time have been studied. An efficient parallel workup procedure was developed to generate a small library (23 compounds) in a short time period. 相似文献
13.
Natural products have been synthesized for billions of years in animals, plants, and microorganisms. As a rule they occur enantiomerically pure. Their chiral character corroborates their use in metabolism or as biologically active agents. Natural products may be insufficient in quality or quantity. They have recently begun to become accessible, either unchanged or modified, by biological synthesis; here, too, they are obtained enantiomerically pure. In the last twenty years chemical synthesis has become a major concern of organic chemists. Their target compounds are primarily enantiomerically pure natural products or biologically active variants thereof. 相似文献
14.
Stark CB Pierau S Wartchow R Hoffmann HM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(4):684-691
A low-temperature (-95 degrees C) protocol for intermolecular cycloadditions of furan to chiral silyloxyallyl cations in dichloromethane is described. Key precursors are open-chain, mixed a-ketoacetals, which are chiral. The resulting [4+3] cycloadducts are densely functionalized and are isolated as single enantiomers in high chemical yield. The yield of the cycloadducts increases with increasing dilution. Three and four stereogenic centres are created in one single step. 相似文献
15.
Lopes NP Stark CB Hong H Gates PJ Staunton J 《Rapid communications in mass spectrometry : RCM》2002,16(5):414-420
Monensin A and B were studied by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) and the fragment ions were confirmed by accurate-mass measurements. Analyses were performed on both a quadrupole time-of-flight (QTOF) and a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer. The analysis revealed that fragment ions were produced by Grob-Wharton fragmentations and pericyclic rearrangements in addition to various simple neutral losses. A study of the protonated and sodiated sodium salt revealed different fragmentation pathways for these species, thus complementary structural information could be gained. A complete fragmentation pathway of monensin A and B protonated sodium salt [(M-H+Na)+H])+) and sodiated sodium salt [(M-H+Na)+Na](+) is proposed. MS(3) analysis confirmed the separate fragmentation pathways. 相似文献
16.
Zusammenfassung Es werden Verbesserungen von Nachweisen von Alkoholen, Chloral, Salicylalkohol, Salicin, Sulfoxylatverbindungen und bestimmten reduzierenden organischen Verbindungen beschrieben, durch die man zu mikroanalytischer Empfindlichkeit und zum Teil auch zu erhöhter Selektivität gelangt.
Summary Improvements of tests for alcohols, chloral, salicylalcohol, salicine, sulfoxylate compounds and certain reducing organic compounds are described, which lead to microanalytical sensibility and sometimes also to enhanced selectivity.
Résumé On décrit des améliorations des méthodes d'identification des alcools, du chloral, de l'alcool salicylique, de la salicine, de composés sulfoxyliques et de combinaisons organiques réductrices définies. Elles atteignent une sensibilité microanalytique et leur sélectivité est parfois accrue.相似文献
17.
Andy Hay James Aguayo Walter Stark Chung-Ho Chen Ugur Camli Lou-Sing Kan 《中国化学会会志》1989,36(2):169-176
Intact human Senses incubated at 5.5 mM (normal) and 35.5 mM glucose were examined by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Lense in 35.5 mM glucose showed an altered metabolic steady-state characterized by a lowered adenosine triphosphate/inorganic orthophosphate ratio. 31P NMR spectroscopy can be used to measure metabolic changes in the lens. This model offers an important means to study dynamic metabolism in the human lens in the setting of diabetic cataractogenesis. 相似文献
18.
Enzymatic hydrolysis of a model triglyceride, palm oil, was carried out with lipase fromRhizopus sp. in microemulsions with varying water content. The microemulsions were based on a nonionic surfactant, pentaethylene glycol monododecyl ether (C12 EO5), buffered water solution and an oil component consisting of isooctane and palm oil at a weight ratio of 20:1. The structure of the microemulsions was characterized using Fourier transform pulsed-gradient spin-echo1H NMR. The rate of reaction decreased as the water content of the reaction medium was increased. The self-diffusion coefficient of water, Dw was found to be constant within the interval 1–20% water. The difference in reactivity is believed to be due to a difference in structure of the palisade layer between water and hydrocarbon microdomains. The nonionic surfactant was demonstrated to be unsuitable for enzymatic reactions since only partial hydrolysis was obtained in all experiments. The surfactant, however, did not cause enzyme deactivation, even at very high concentrations. 相似文献
19.
This paper presents a simple, self‐contained account of Gårding's theory of hyperbolic polynomials, together with a recent convexity result of Bauschke‐Güler‐Lewis‐Sendov and an inequality of Gurvits. This account begins by establishing some new results. The first concerns the existence of a pointwise arrangement of the eigenvalues so that they become global real analytic functions. The second asserts that the associated “branches” are independent of the choice of hyperbolic direction. © 2013 Wiley Periodicals, Inc. 相似文献
20.
Charles E. Carraher JR. 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1293-1356
This review emphasizes the breadth of metallic and metallic-like polymers evaluated as to thermal properties. Techniques usefully applied to particular systems are noted with the aim of suggesting their application to other systems. 相似文献