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111.
Molecular N2 emission, observed from an Ar(3Po, 2) and Xe(3P2) + N2 flowing afterglow apparatus, indicates that the energy pooling reaction by 2N2(A 3Σ+u) generates the emission from the Herman infrared system, which is an unassigned nitrogen band system. A lower limit to the formation rate constant for the upper state of the Herman infrared system was found to be 2.5 × 10-11 cm3 molecule?1 s?1. The information presented here may help in the identification of the upper and lower states of the emission system. The 2N2(A) energy pooling reaction also forms N2(B3 Πg, v? 8) but a rate constant cannot be assigned from the present data. 相似文献
112.
Pucci V Monteagudo E Bonelli F 《Rapid communications in mass spectrometry : RCM》2005,19(24):3713-3718
A high-throughput liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) assay using automated sample preparation has been developed for the determination of valproic acid (VPA) in mouse plasma. A liquid-handling system was programmed to prepare calibration standard solutions in plasma, as well as quality controls and clinical samples. Plasma protein precipitation was performed on a 96-well plate, and the collected supernatant was directly injected into a reversed-phase LC/ESI-MS/MS system in the negative ionization mode. The calibration curve for VPA was linear over a dynamic range of 0.15-100 microg/mL. The limit of detection was 75 ng/mL and the lower limit of quantitation was 150 ng/mL. Intra- and inter-day validation assays of the semi-automated plasma analysis showed satisfactory accuracy and precision. 相似文献
113.
114.
Winfried Wendelin Edith Gößnitzer Dalal Abou El Ella 《Monatshefte für Chemie / Chemical Monthly》2000,131(4):353-374
Summary. The cyclization reactions of trans-3a-hexahydro-2-benzimidazolamine with 2-alkylidene- and 2-benzylidenecyclohexanones and α-tetralones, respectively, yield
mixtures of two isomeric condensates each. Thorough high resolution NMR analyses (1H and 13C NMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, and 1D NOE difference spectra) revealed that the corresponding isomers are in all cases linearly fused diastereomeric
12α- and 12β-substituted trans-6aα-dodecahydrobenzimidazo[2,1-b]quinazolines and 7α-substituted trans-8aβ- and trans-8aα-decahydrobenzimidazo[2,1-b]benzo[h]quinazolines, respectively. The formation of corresponding angularly fused regioisomers was not observed so far. The stereochemistry
and the tautomerism of some bases and their hydrochlorides as well as the regiospecific course of the cyclization reactions
are discussed. Biological tests showed that the novel compounds don’t exert remarkable antibacterial and antimycotic effects.
Received November 3, 1999. Accepted November 30, 1999 相似文献
115.
Zusammenfassung. Die Reaktion von racemischem trans-Hexahydrobenzimidazol-2-amin mit drei ausgew?hlten vinylogen Ketonen unter milden Bedingungen wurde untersucht. Nur im Fall
der Umsetzung mit 4-Phenyl-3-buten-2-on konnten Cycloadditionsprodukte isoliert werden. Diese sind laut NMR-Analysen Gemische
von zwei der acht m?glichen Diastereomeren, n?mlich von rac-2β-Methyl-4β-phenyl-trans-5aα- und trans-5aβ-decahydropyrimido[1,2-a]benzimidazol-2α-ol. Bei Umsetzungen des Amins mit Phenylbutenon bei erhoühten Temperatur sowie mit, 2-Methyl-1-phenyl-1-penten-3-on
und 4′-Chlorchalkon bildeten sich Gemische entsprechend substituierter rac-4α-Phenyl-trans-5aβ- und trans-5aα-octahydropyrimido[1,2-a]benzimidazole. Struktur und Stereochemie der Titelverbindungen und ihrer Hydrochloride wurden anhand NMR-spektroskopischer
Untersuchungen aufgekl?rt. Die Ringschlu?reaktionen verlaufen in allen F?llen gleichgerichtet regio-, jedoch nicht diastereoselektiv.
Versuche zur Beeinflussung der Regio- und/oder Diastereoselektivit?t der Cyclisierungsreaktion durch Variation der Reaktionsbedingungen
hatten keinen Erfolg.
Synthesis and Structure Elucidation of Pyrimidobenzimidazoles and Fused Derivatives III [1,2]. Decahydropyrimido[1,2- a ]benzimidazol-2-oles and Octahydropyrimido[1,2- a ]benzimidazoles
Summary. The reaction of racemic trans-hexahydrobenzimidazol-2-amine with three vinylogous ketones under mild conditions was studied. Only in the case of 4-phenyl-3-buten-2-one cycloaddition products could be isolated. According to NMR spectroscopy they consist of mixtures of two of eight possible diastereomers: rac-2β-methyl-4β-phenyl-trans-5aα- and trans-5aβ-decahydropyrimido[1,2-a]benzimidazol-2α-ole. Reaction of the amine with the butenone at higher temperature and with, 2-methyl-1-phenyl-1-penten-3-one, and 4′-chlorochalcone afforded mixtures of two diastereomers each, which turned out as rac-4α-phenyl-trans-5aβ- and trans-5aα-octahydropyrimido[1,2-a]benzimidazoles. Complete structural and stereochemical assignments of the title compounds and their hydrochlorides were established by NMR spectroscopic investigations. The results showed that all investigated cyclization reactions proceeded regioselectively with equal orientation of the components, but not diastereoselectively. Variation of the reaction conditions did influence neither regio- nor diastereoselectivity.
Received October 19, 2000. Accepted October 30, 2000 相似文献
116.
Edith Gößnitzer Winfried Wendelin Karl Schermanz Karin Frieberger 《Monatshefte für Chemie / Chemical Monthly》2001,132(9):1081-1093
Summary. The reaction of 2-benzylidenecyclohexanone and 1-(4-methoxyphenyl)-2-methyl-1-penten-3-one with guanidine did not yield the
expected 4-phenylhexahydro-2-quinazolinamine and 4-(p-methoxyphenyl)-dihydro-2-pyrimidinamine, respectively, but nitrogen-free products which turned out as [3+3]- and [4+2]-cycloadducts
of two molecules of the applied vinylogous ketone each. According to elemental analyses, mass spectra, and, in particular,
NMR analyses (1H and 13CNMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, NOESY, and 1D NOE difference spectra), the prepared dimers were identified as racemic (5E)-5-benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α- propionylcyclohexanone, respectively. Structure and stereochemistry of the dimers
are elucidated, and mechanisms for their formation are proposed.
Received April 11, 2001. Accepted (revised) May 18, 2001 相似文献
117.
118.
Squares of characters and finite groups 总被引:1,自引:0,他引:1
Let G be a finite group and χ be an irreducible complex character. We study the character χ2 in the case that χ(1) is a prime power. 相似文献
119.
120.
This review presents the structure, biological activity, biosynthetic studies and, where applicable, references to syntheses of 81 marine alkaloids containing either tetra-, hexa- or octa-hydrogenated variants of pyrrolo[4,3,2-de]quinoline, pyrrolo[4,3,2-de]pyrrolo[2,3-h]quinoline and pyrido[2,3-h]pyrrolo[4,3,2-de]quinoline core skeletons. The literature describing the isolation of pyrroloiminoquinones, and related metabolites, from marine sponges is littered with taxonomic inconsistencies and recent efforts to clarify the taxonomy of the sponges that produce this group of metabolites are discussed. 相似文献