- Enantioselective homogeneous hydrogenation of monosubstituted pyridines and furans
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The first case of an enantioselective hydrogenation of monosubstituted pyridines and furans with homogeneous rhodium diphosphine catalysts with low but significant enantioselectivities and catalyst activities is reported. Best enantioselectivities (ees of 24-27%) were obtained for the hydrogenation of 2-and 3-pyridine carboxylic acid ethyl ester and 2-furan carboxylic acid with catalysts prepared in situ from [Rh(nbd)2]BF4 and the chiral ligands diop, binap, or ferrocenyl diphosphines of the josiphos type. Turnover numbers (ton) were in the order of 10-20, turnover frequencies (tof) usually 1-2 h-1. Diphosphines giving 6-or 7-ring chelates led to higher ees than 1,2-diphosphines; otherwise, no clear correlation between ligand properties and catalytic performance was found. In some experiments black precipitates were observed at the end of the reaction, indicating the decomposition of the homogeneous catalysts for certain ligand/metal/ substrate combinations.
- Studer, Martin,Wedemeyer-Exl, Christina,Spindler, Felix,Blaser, Hans-Ulrich
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- Development, synthesis and structure–activity-relationships of inhibitors of the macrophage infectivity potentiator (Mip) proteins of Legionella pneumophila and Burkholderia pseudomallei
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The bacteria Burkholderia pseudomallei and Legionella pneumophila cause severe diseases like melioidosis and Legionnaire's disease with high mortality rates despite antibiotic treatment. Due to increasing antibiotic resistances against these and other Gram-negative bacteria, alternative therapeutical strategies are in urgent demand. As a virulence factor, the macrophage infectivity potentiator (Mip) protein constitutes an attractive target. The Mip proteins of B. pseudomallei and L. pneumophila exhibit peptidyl-prolyl cis/trans isomerase (PPIase) activity and belong to the PPIase superfamily. In previous studies, the pipecolic acid moiety proved to be a valuable scaffold for inhibiting this PPIase activity. Thus, a library of pipecolic acid derivatives was established guided by structural information and computational analyses of the binding site and possible binding modes. Stability and toxicity considerations were taken into account in iterative extensions of the library. Synthesis and evaluation of the compounds in PPIase assays resulted in highly active inhibitors. The activities can be interpreted in terms of a common binding mode obtained by docking calculations.
- Seufert, Florian,Kuhn, Maximilian,Hein, Michael,Weiwad, Matthias,Vivoli, Mirella,Norville, Isobel H.,Sarkar-Tyson, Mitali,Marshall, Laura E.,Schweimer, Kristian,Bruhn, Heike,R?sch, Paul,Harmer, Nicholas J.,Sotriffer, Christoph A.,Holzgrabe, Ulrike
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p. 5134 - 5147
(2016/10/24)
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- Rigid Mn(II) chelate as efficient MRI contrast agent for vascular imaging
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The aza-semi-crown pentadentate ligand rigidified by pyridine and piperidine rings was designed and synthesized. It can react with Mn(II) in water to form complex with improved longitudinal relaxivity, leading to efficient signal intensity enhancement of vascular vessels under a clinical magnetic resonance imaging scanner.
- Su, Hongying,Wu, Changqiang,Zhu, Jiang,Miao, Tianxin,Wang, Dan,Xia, Chunchao,Zhao, Xuna,Gong, Qiyong,Song, Bin,Ai, Hua
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supporting information
p. 14480 - 14483
(2013/01/16)
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- A new and convenient synthesis of 1-benzyl-1-azaspiro [5.5] undecan-7-one: A formal synthesis of (±)-perhydrohistrio-nicotoxin
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A rapid, three-step synthesis of the title compound 3 in 40% overall yield from (±)-pipecolinic acid, is described.
- Compain,Gore,Vatele
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p. 3075 - 3080
(2007/10/03)
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