使用化学,制备了简单的大环假肽动力学系统,该系统包含类似于已知的铵阳离子受体的环状结构。测试了一系列铵盐作为模板,并根据使用的模板以不同程度扩增了预期的受体。与冠醚的竞争性非共价相互作用被用来原位证明模板化系统仍然是动态的。ESI-MS和1 H ROESY实验证明了客体-客体复合物的形成。各种模板对分离的受体的相对亲和力与它们对文库组成产生的作用密切相关。
Tandem Formation and [2,3] Rearrangement of Methylene Ammonium Ylides Derived from Amines and the Simmons−Smith Reagent
作者:Varinder K. Aggarwal、Guang yu Fang、Jonathan P. H. Charmant、Graham Meek
DOI:10.1021/ol034404i
日期:2003.5.1
[reaction: see text] Zinc-complexed methylene ammoniumylides are formed from tertiary amines and the Simmons-Smith reagent. These stable entities can be activated with n-BuLi to allow reactions typical of ammoniumylides such as [2,3] rearrangements. In the case of oxazolidine 12, ylide formation, activation, and subsequent [2,3] rearrangement was highly efficient and occurred with very high diastereoselectivity
The synthesis and properties of a new class of anhydrous quaternary ammonium fluorides, based on the rigid skeleton azabicyclo[2.2.2]octane, is described. Compounds 2a–d were easily prepared by passing the corresponding ammonium iodides over fluoride-based resin followed by drying their hydrated form at 100 or 140 °C under reduced pressure. The stability (experimental and theoretical study), solubility
Hydrogen bonding Part 48. IR and thermodynamic study of the lower hydrates of N-methylquinuclidinium iodide, bromide, chloride, fluoride, and hydroxide; evidence for a temperature-dependent rearrangement of hydrogen bonds in the chloride monohydrate
作者:Kenneth M. Harmon、Barbara A. Southworth
DOI:10.1016/0022-2860(93)80204-9
日期:1993.10
absorptions of a C2h (H2O · Cl−)2 planar cluster; however, above this temperature this spectrum is replaced with an entirely different spectrum tentatively assigned to extended “linear” hydrogen bonding. The bromide and iodide show only the linear type of IR spectra. Dissociation vapor pressure measurements of the low temperature form of the chloride give an unreasonably high value for ΔHdis° (27.56
The rapid and efficient synthesis of 1-alkylquinuclidinium (1-alkyl-1-azabicyclo[2.2.2]octane) and 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane iodides are described. The products were characterized by 1H NMR spectra and elemental analysis.
Self-folding cavitands: structural characterization of the induced-fit model
作者:Agustí Lledó、Julius Rebek Jr.
DOI:10.1039/b927031k
日期:——
Deletion of structural elements in cavitand receptors is used to evaluate the thermodynamic and kinetic parameters of binding in these hosts. The use of a bulky guest showcases the importance of host–guest shape adaptations in the molecular recognition process.