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41.
Christie G. Enke Richard A. Yost 《Journal of the American Society for Mass Spectrometry》2013,24(9):1319-1323
Our long-time association with Jim Morrison and the work that came from it is the result of a series of fortunate coincidences. We are pleased to be able to share recollections here of our interactions with Jim and how his life and work have influenced us and the field of mass spectrometry. Graphical Abstract
? 相似文献
42.
Intrinsic to the process of high-order harmonic generation is the creation of plasma and the resulting spatiotemporal distortions of the driving laser pulse. Inside a high-finesse cavity where the driver pulse and gas medium are reused, this can lead to optical bistability of the cavity-plasma system, accumulated self-phase modulation of the intracavity pulse, and coupling to higher-order cavity modes. We present an experimental and theoretical study of these effects and discuss their implications for power scaling of intracavity high-order harmonic generation and extreme ultraviolet frequency combs. 相似文献
43.
Elisabetta Maluta David Yost 《Journal of Mathematical Analysis and Applications》2019,469(2):1080-1087
We prove that every Banach space which admits an unconditional basis can be renormed to contain a constant width set with empty interior, thus guaranteeing, for the first time, existence of such sets in a reflexive space. In the isometric case we prove that normal structure is characterized by the property that the class of diametrically complete sets and the class of sets with constant radius from the boundary coincide. 相似文献
44.
A facile and efficient four-component anti-selective direct aldol addition of thioester enolates has been developed that is fully compatible with enolizable aldehydes and able to be conducted using untreated reagent-grade CH2Cl2 open to the air. The thioester enolates are generated in situ via an acylation/conjugate addition sequence using commercially available PhSLi and acryloyl chloride, thus avoiding prior enolate formation while maintaining complete chemoselectivity. The organosulfur products are convertible into various polyketide-based structures. 相似文献
45.
Direct carbon-carbon bond formation via soft enolization: aldol addition of α-halogenated thioesters
Yost JM Alfie RJ Tarsis EM Chong I Coltart DM 《Chemical communications (Cambridge, England)》2011,47(1):571-572
α-Halo thioesters undergo soft enolization and syn-selective direct aldol addition to aldehydes in the presence of MgBr(2)·OEt(2) and i-Pr(2)NEt to produce α-halo-β-hydroxy thioesters. 相似文献
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47.
Todd A. Gillespie Richard A. Yost 《Journal of the American Society for Mass Spectrometry》1990,1(5):389-396
Some intriguing discoveries were made concerning the collision-activated dissociation behavior of the derivatized carboxylate anions of PGE2 and PGF2α. The carboxylate anion [MPFB]? formed from electron-capture negative chemical ionization of the pentafluorobenzyl ester-trimethylsilyl derivative of PGF2α showed little fragmentation under typical collision gas pressures and energies (<2.0 mtorr N2 and <20 eV). In contrast, the daughter spectra of the carboxylate anion of the methoxime-pentafluorobenzyl ester-trimethylsilyl derivative of PGE2 produced many intense fragments under the same conditions. 相似文献
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Bajpai L Varshney M Seubert CN Stevens SM Johnson JV Yost RA Dennis DM 《Journal of the American Society for Mass Spectrometry》2005,16(6):814-824
Propofol (2,6-diisopropyl phenol) is a widely used intravenous anesthetic. To define its pharmacokinetics and pharmacodynamics, methods for its quantitation in biological matrixes have been developed, but its pattern of mass spectral fragmentation is unknown. We found that fragmentation of the [M - H](-) ion (m/z 177) of propofol in both APCI MS/MS and ESI MS/MS involves the stepwise loss of a methyl radical and a hydrogen radical from one isopropyl side chain to give the most intense product ion, [M -H - CH(4)](-), at m/z 161. This two-step process is also the preferred mode of fragmentation for similar branched alkyl substituted phenols. This mode of fragmentation of the [M - H](-) ion is supported by three independent lines of evidence: (1) the presence of the intermediary [M - H - CH(3)](-) radical ion under conditions of reduced collision energy, (2) the determination of the mass of the predominant [M - H - CH(4)](-) product ion by high resolution mass spectrometry, and (3) the pattern of product ions resulting from further fragmentation of the [M - H - CH(4)](-) product ion. Phenols with a single straight chain alkyl substituent, in contrast, undergo beta elimination of the alkyl radical irrespective of the length of the alkyl chain, yielding the most intense product ion at m/z 106. This product ion represents a special case of a stable intermediary radical for the two-step process described for branched side chains, because further elimination of a hydrogen radical from the beta carbon is not possible. 相似文献