Organocatalytic Asymmetric Conjugate Addition of Aldehydes to Nitroolefins: Identification of Catalytic Intermediates and the Stereoselectivity-Determining Step by ESI-MS
Looking back: The asymmetricorganocatalytic 1,4‐addition of aldehydes to nitroolefins was studied by ESI‐MS. Analysis of the back reaction starting from quasienantiomeric mass‐labeled 1,4‐adducts (see scheme) provided conclusive evidence for an enamine rather than an enol mechanism, and allowed identification of the enantioselectivity‐determining step.
METHOD FOR PRODUCING FIVE-MEMBERED RING-CONTAINING COMPOUND
申请人:Hayashi Yujiro
公开号:US20140051874A1
公开(公告)日:2014-02-20
The present invention provides a method that allows production of stereospecific and asymmetrical five-membered ring-containing compounds serving as synthetic intermediates for formation of five-membered rings of prostaglandins and the like, with high yield and excellent stereoselectivity in terms of diastereoselectivity and enantioselectivity in a short process without requiring troublesome procedures such as optical resolution. The method for producing a five-membered ring-containing compound includes a cyclization step of condensing and cyclizing an α,β-unsaturated nitro compound represented by the following chemical formula (I) with a 1,4-butanedione compound, in the presence of a catalyst formed by a compound having a pyrrolidine ring and an optically active α-carbon relative to the nitrogen on the ring, in a water-insoluble organic solvent and/or a non-oxygen atom-containing water-soluble organic solvent so as to produce the five-membered ring-containing compound represented by the following chemical formula (II).
Organocatalytic Synthesis of Triflones Bearing Two Non‐Adjacent Stereogenic Centers
作者:Alena Budinská、Helma Wennemers
DOI:10.1002/anie.202300537
日期:——
An efficient organocatalytic method to synthetically versatile chiral triflones with two non-adjacent stereogenic centers was developed. The work uses, for the first time, α-aryl vinyl triflones as Michael acceptors in stereoselective catalysis. Control over the absolute configuration is achieved by a catalyst-controlled stereoselective C−C bond formation-protonation sequence.
Influence of the <i>Trans</i>/<i>Cis</i> Conformer Ratio on the Stereoselectivity of Peptidic Catalysts
作者:Tobias Schnitzer、Helma Wennemers
DOI:10.1021/jacs.7b06194
日期:2017.11.1
numerous versatile peptidic catalysts have been developed that bear Xaa-Pro amide bonds. Due to the many degrees of freedom within even short peptides, the design and optimization of peptidic catalysts by rational structural modifications is difficult. We envisioned that control over the trans/cis amidebond ratio may provide a tool to optimize the catalytic performance of peptidic catalysts. Here, we
Xaa-Pro 键的反式/顺式异构化是几种酶结构和功能的关键。近年来,已经开发了许多带有 Xaa-Pro 酰胺键的多功能肽催化剂。由于即使是短肽也有很多自由度,通过合理的结构修饰来设计和优化肽催化剂是很困难的。我们设想控制反式/顺式酰胺键比率可以提供一种工具来优化肽催化剂的催化性能。在这里,我们研究了酰胺键构象对 H-Pro-Pro-Xaa-NH2 型肽催化剂在共轭加成反应中的立体选择性的影响。三肽中的中间 Pro 残基被不同环大小的类似物(氮杂环丁烷羧酸、Aze 和哌啶羧酸,Pip) 在不同的溶剂中产生不同的反/顺比。研究揭示了反式/顺式酰胺键比率与结构相关肽催化剂的对映选择性和非对映选择性之间存在直接相关性。这些见解导致 Hd-Pro-Pip-Glu-NH2 被鉴定为一种高反应性和立体选择性胺基催化剂,它允许在低至 0.05 mol% 的催化剂存在下进行 CC 键的形成,这是最低的催化