制备了四个新颖的C 2对称对映体纯的,在立体异构中心含有亲脂性链的手性吡啶-18-冠-6型大环化合物。朝向的对映体的新的配位体的对映选择性d - , -升-氨基甲酸甲基酯衍生物也通过确定1分1 H NMR滴定法。这些新的大环化合物已被证明是d和l氨基酸甲酯盐酸盐的强络合剂(K ass高达13590 M -1和∆ G 0高达23.3 kJ mol -1和选择性比:80: 20)通过1 H NMR滴定方法。这些大环主体在具有0.25%CD 3 OD的CDCl 3中显示出对缬氨酸甲酯盐酸盐的d-对映异构体的对映选择性结合,其中K d / K 1高达5.08 。
Chiral C2-symmetric η6-p-cymene-Ru(II)-phosphinite complexes: Synthesis and catalytic activity in asymmetric reduction of aromatic, methyl alkyl and alkyl/aryl ketones
Abstract Chiral C2-symmetric bis(phosphinite) ligands and their binuclearruthenium(II) complexes have been synthesized and used as catalysts in the ruthenium-catalyzed asymmetrictransferhydrogenation of aromatic, methyl alkyl and alkyl/aryl ketones using 2-propanol as both the hydrogen source and solvent in the presence of KOH. Under optimized conditions, all complexes showed high catalytic activity
Combining Magnetic Resonance Spectroscopies, Mass Spectrometry, and Molecular Dynamics: Investigation of Chiral Recognition by 2,6-di-<i>O</i>-Methyl-β-cyclodextrin
the structurally related amine precursors of nitroxides. NOE data suggested that inclusion of the stereogenic center in the DM-beta-CD cavity occurs only when the R substituent linked to the chiral carbon contains an aromatic ring. For these types of complexes, molecular dynamics simulation indicated that the depth of penetration of the stereogenic center into the cyclodextrincavity is determined by
EPR 光谱已被用于研究 heptakis-(2,6-O-二甲基)-β-环糊精 (DM-β-CD) 和不同对映异构体对的通用结构 PhCH2NO.CH(R) 手性氮氧化物之间的复合物的形成R'。自由基和所含自由基浓度的准确平衡测量提供了这些氮氧化物的结合常数值。DM-β-CD 复合物的立体化学与复合热力学之间的关系通过将 EPR 数据与 1H-1H NOE 测量相关联,对 DM-β-CD 和结构相关的硝基氧胺前体之间的复合物进行了测量。NOE 数据表明,仅当与手性碳相连的 R 取代基包含芳香环时,才会在 DM-β-CD 腔中包含立体中心。对于这些类型的复合物,分子动力学模拟表明立体中心渗透到环糊精腔中的深度由不对称碳上的第二个取代基 (R') 的性质决定,并且是观察到的手性选择性的原因。质谱分析表明,对于目前研究的胺,通过 ESI-MS 检测到 CD 与质子化胺的静电外部加合物。
A short enantioselective synthesis of (−)-bestatin via l-proline-catalyzed α-amination of an aldehyde
作者:Shyla George、Gurunath S. Suryavanshi、Arumugam Sudalai
DOI:10.1016/j.tetlet.2008.09.054
日期:2008.11
A short and high yielding enantioselective synthesis of (−)-bestatin, a naturally occurring aminopeptidase inhibitor, is described via l-proline-catalyzed asymmetric α-amination of 3-phenylpropionaldehyde as the key reaction. The methodology also involves a Pd-catalyzed intramolecular cyclization of an allylic acetate giving a trans-oxazoline in a highly diastereoselective manner (dr > 14:1).
Synthesis, characterization and first application of chiral <i>C</i>
<sub>2</sub>
-symmetric bis(phosphinite)-Pd(II) complexes as catalysts in asymmetric intermolecular Heck reactions
A series of new chiral C2‐symmetric bis(phosphinite) ligands and their palladium(II) complexes have been synthesized and for the first time used as catalysts in the palladium‐catalysedasymmetric intermolecular Heck coupling reactions of 2,3‐dihydrofuran with iodobenzene or aryl triflate. Under optimized conditions, products were obtained with high conversions and moderate to good enantioselectivities
ruthenium catalyst systems generated in situ from [Ru(η6-p-cymene)(μ-Cl)Cl]2 complex and chiral C 2-symmetric bis(phosphinite) ligands based on amino alcohol derivatives were employed in the asymmetric transfer hydrogenation of aromatic ketones to give the corresponding optically active alcohols in high yield. The best results were obtained in the [Ru(η6-p-cymene)(μ-Cl)Cl]2 and (2S)-2-[benzyl(2-benzyl[(