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1.
Casey Chun Zhou Eric J. Stoner Kent D. Stewart L. Steven Hollis Edmund D. Matayoshi Gregory M. Brill 《Tetrahedron》2004,60(47):10611-10618
Oritavancin is a semi-synthetic glycopeptide antibiotic which is structurally related to vancomycin. When oritavancin bisphosphate is dried in vacuo with heat, a new compound forms. This new compound is stable only in the solid state and reverts to oritavancin in solution. Highly enriched samples of this compound were obtained by preparative HPLC and the structure of this compound was elucidated by using one and two-dimensional (1H and 13C) NMR spectroscopy in conjunction with computer-assisted molecular modeling. It has been determined that oritavancin adopts a conformation similar to that of vancomycin in solution, while the new compound is the unnatural R-AB-biaryl atropisomer of oritavancin. This is the first observation and isolation of an AB-biaryl atropisomer in an intact member of the vancomycin family of glycopeptide antibiotics. 相似文献
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A model in which strongness of is indestructible under + -weakly closed forcing notions satisfying the Prikry condition is constructed. This is applied to solve a question of Hajnal on the number of elements of {
|2
<}. 相似文献
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Moti Gitik 《Israel Journal of Mathematics》1995,92(1-3):61-112
The strength of precipitousness, presaturatedness and saturatedness of NSκ and NS κ λ is studied. In particular, it is shown that:
- The exact strength of “ $NS_{\mu ^ + }^\lambda $ for a regularμ > max(λ, ?1)” is a (ω,μ)-repeat point.
- The exact strength of “NSκ is presaturated over inaccessible κ” is an up-repeat point.
- “NSκ is saturated over inaccessible κ” implies an inner model with ?αo(α) =α ++.
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The spontaneous decarboxylation of 0.5 m aqueous α‐alanine solutions as a function of pH (1–9 at 320°C, where neutrality is approximately 6) was determined with a flow reactor at 280–330°C and 275 bar by FT‐IR spectroscopy. The kinetics for the cationic and anionic forms have not been previously reported. The rate constants for the cationic form [CH3(NH3+)CHCO2H], the anionic form [CH3(NH2)CHCO2?], and the zwitterion form [CH3(NH3+)CHCO2?] were obtained and followed the first‐order rate law. The rate of decarboxylation of the zwitterion is three times greater than that of the cationic and anionic forms in the temperature and pH ranges of study. The corresponding Arrhenius parameters were determined and compared with previously reported data. The addition of KCl (1 and 2 m) at the natural pH of α‐alanine resulted in a reduction of the decarboxylation rate, suggesting that the transition state is less polar than the zwitterion and/or that the activity of the zwitterion has been reduced. The α‐alanine solution is therefore somewhat more robust in solutions of high ionic strength, such as seawater, than it is in pure water. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 271–277, 2002 相似文献
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We continue the study of tall cardinals and related notions begun by Hamkins in 2009 and answer three of his questions posed in that paper. 相似文献
10.
Marvin H. Caruthers Wolfgang Brill Douglas J. Dellinger 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):549-553
Abstract Methods for the rapid synthesis of DNA and RNA are described. The procedures involve using nucleoside phosphoramidites as synthons and silica as a polymeric support. Additionally, a novel reaction involving nucleoside O-alkyl methylphosphonothioates is described. 相似文献