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81.
82.
[reaction: see text] Treatment of the anion derived from the ring-fused gem-dichlorocyclopropane 4c with silver tetrafluoroborate afforded the spirocyclic compound 17 in 74% yield. Product 17 was readily converted, over three steps, into the beta-iodoethyl derivative 20 and treatment of this latter compound with n-Bu(3)SnH then afforded, in 93% yield and via a radical addition/elimination sequence, compound 2 incorporating the ABCD framework of the aromatic erythrina alkaloids. 相似文献
83.
David J. Harvey Jaak Jaeken Mike Butler Alison J. Armitage Pauline M. Rudd Raymond A. Dwek 《Journal of mass spectrometry : JMS》2010,45(5):528-535
Negative ion CID spectra of N‐linked glycans released from glycoproteins contain many ions that are diagnostic for specific structural features such as the detailed arrangement of antennae and the location of fucose residues. Identification of such ions requires reference glycans that are often difficult to acquire in a pure state. The recent acquisition of a sample of N‐glycans from a patient lacking the enzyme N‐acetylglucosaminyltransferase‐2 provided an opportunity to investigate fragmentation of glycans lacking a 6‐antenna. These glycans contained one or two galactose‐N‐acetylglucosamine‐chains attached to the 3‐linked mannose residue of the trimannosyl‐chitobiose core with and without fucose substitution. The spectra from the patient sample clearly defined the antenna distribution and showed striking differences from the spectra of isomeric compounds obtained from normal subjects. Furthermore, they provided additional information on previously identified antenna‐specific fragment ions and indicated the presence of additional ions that were diagnostic of fucose substitution. Glycans obtained from such enzyme‐deficient patients can, thus, be a valuable way of obtaining spectra of specific isomers in a relatively pure state for interpretation of mass spectra. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
84.
Ohne Zusammenfassung 相似文献
85.
Yves Langlois Alain Petit Pauline Rémy Marie-Christine Scherrmann Cyrille Kouklovsky 《Tetrahedron letters》2008,49(39):5576-5579
Camphor-derived sulfonylhydrazines proved to be very active for organocatalyzed Diels-Alder cycloadditions with cyclopentadiene. Good chemical yields and enantiomeric excesses up to 89% and 88% are obtained for endo/exo adducts. 相似文献
86.
Ryckebusch A Gilleron P Millet R Houssin R Lemoine A Pommery N Grellier P Sergheraert C Hénichart JP 《Chemical & pharmaceutical bulletin》2005,53(10):1324-1326
Protein farnesyltransferase of Plasmodium falciparum is a potential target in the treatment of malaria for which increased drug resistance is observed. The design, synthesis and evaluation of a series of N-(4-piperidinyl)benzamides is reported. The most potent compounds showed in vitro activity against the parasite at submicromolar concentrations. 相似文献
87.
A new transient regime in the relaxation towards absolute equilibrium of the conservative and time-reversible 3D Euler equation with a high-wave-number spectral truncation is characterized. Large-scale dissipative effects, caused by the thermalized modes that spontaneously appear between a transition wave number and the maximum wave number, are calculated using fluctuation dissipation relations. The large-scale dynamics is found to be similar to that of high-Reynolds number Navier-Stokes equations and thus obeys (at least approximately) Kolmogorov scaling. 相似文献
88.
[reaction: see text] A series of experiments are described that suggest that the Rh-catalyzed reductive aldol reaction proceeds by addition of a Rh(I) hydride, generated in situ, to the reacting acrylate followed by a stereochemistry-controlling aldol addition reaction. On the basis of this hypothesis, reaction conditions are engineered that allow for increased substrate scope. 相似文献
89.
Ngoc Hoa Tran Huy Pauline Chaigne Ingrid Dchamps Louis Ricard Franois Mathey 《Heteroatom Chemistry》2005,16(1):44-48
The 1,2‐dihydro‐1,2‐diphosphinine decacarbonylditungsten complex 1 has been used as a synthetic equivalent of the corresponding 1,2‐dianion 2 . These two 1,2‐positions can be linked by a (CH2)4 bridge to yield a [4.4.0] bicyclic structure 6 whose identity has been confirmed by X‐ray crystal structure analysis. Alternatively, two ω‐iodohexyl chains can be grafted onto these positions and the resulting diiodo derivative 9 transformed into a long‐chain bis‐phosphine 10 by reaction with lithium diphenylphosphide. This bis‐phosphine gives a chelate complex with PdCl2 whose trans‐stereochemistry was established by X‐ray crystal structure analysis. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:44–48, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20073 相似文献
90.