Synthesis and Catalytic Activities of (<i>S</i>)-1-formylpyrrolidine-2-carboxylic Acid Derivatives for the Enantioselective Reductions of Both a Ketone and a Ketimine
作者:Zhenfei Chen、Anjiang Zhang、Lixue Zhang、Jing Zhang、Xinxiang Lei
DOI:10.3184/030823408x318433
日期:2008.5
as chiral organocatalysts in the asymmetric reduction of both ketone 2 and ketimine 3. These organic activators afforded good to moderate enantioselectivities in the asymmetric reductions of both the ketone and the ketimine. Among them, organic activator 6h displayed the best efficiency, affording a 84% yield and 41% ee in the reduction of the ketone and 75% yield and 52% ee in the reduction of the ketimine
Self-Assembled Multi-Component Catenanes: Structural Insights into an Adaptable Class of Molecular Receptors and [2]-Catenanes
作者:Mee-Kyung Chung、Peter S. White、Stephen J. Lee、Marcey L. Waters、Michel R. Gagné
DOI:10.1021/ja302345n
日期:2012.7.18
Under acidic conditions (50 equiv of TFA), combinations of hydrazide A-B monomers self-assemble into octameric [2]-catenanes with high selectivity for [1(3)2](2), where 1 is a D-Pro-X (X = Aib, Ac(4)c, Ac(6)c, L-4-Cl-PhGly)-derived monomer and 2 is an L-Pro'-L-arylGly (Pro' = Pro, trans-F-Pro, trans-HO-Pro, aryl = naphthyl, phenyl)-derived monomer. Five different combinations of monomers were studied by X-ray crystallography. In each case, the unique aryl glycine unit is located in the core of the structure where the aryl ring templates a CHI-pi-CH sandwich. Analysis of metrical parameters indicates that this core region is highly conserved, while the more peripheral zones are flexible. H-1 NMR spectroscopy indicate that the solid-state structures are largely retained in solution, though several non-C-2-symmetric compounds have a net C-2-symmetry that indicates accessible dynamic processes. Catenane dynamic processes were additionally probed through H/D exchange, with the core being inflexible relative to the peripheral structure. Mass spectrometry was utilized to identify the constitutional isomerism in the minor asymmetric [1(5)2(3)] catenanes.