Asymmetric synthesis of azetidin-2-ones by [2+2] cycloaddition using chiral imines derived from d-(+)-glucose

Asymmetric synthesis of β-lactams by the [2+2] cycloaddition of ketenes with chiral imines derived from d-(+)-glucose was carried out; predominantly cis-β-lactams were formed with very high diastereoselectivity. The stereochemistry at C-3 and C-4 was established as 3S and 4R from the known absolute configuration of the sugar moiety.     

有机小分子催化的烯酮的不对称环加成反应

重点从立体选择性和催化机理方面,总结了不同的有机小分子催化剂在烯酮的[2+2]和[4+2]不对称环加成反应中的应用.     

具有生物活性的色满衍生物不对称合成研究

色满衍生物在自然界中广泛存在,并且大多数具有生物活性。这些具有生物活性的色满衍生物又大多具有手性,因此有关它们的不对称合成已经引起了有机合成工作者的广泛关注。合成色满衍生物的关键是构建含有手性中心的色满环。本文根据色满环构建方式的不同进行分类,概述了近十几年来合成手性色满衍生物的最新方法, 侧重讨论了各种合成方法在合成立体结构专一的色满环时的特点。     

Asymmetric Electrochemical Catalysis

Asymmetric electrochemical catalysis, an emerging frontline in asymmetric catalysis and electro-organic synthesis, is summarized. Representative works are classified, with respect to the external chiral resources, including chiral media, chiral mediator, chiral catalyst, and chiral electrode. This concept article is expected to provide readers with the general concepts and perspectives of each chiral electrochemical catalysis mode, and to indicate the potential and future development of asymmetric electrochemical catalysis.     

非甾体消炎药萘普生不对称合成研究

萘普生[(S)-(+)-S-(6'-甲氧基-2'-萘基)丙酸]是一种非常重要的非甾体消炎镇痛药。以(2R,3R)-酒石酸二甲酯为手性辅助剂,2-甲氧基萘经溴代、丙酰化、缩酮化、不对称溴化、水解、立体专一性重排和催化氢转移氢解等反应合成了光学活性萘普生,化学收率44%。制备的萘普生的光学纯度([α]~D^2^5=+63.5ⅲ)符合中华人民共和国药典(1995年版)的要求。     

Asymmetric synthesis of some new tetrahydroisoquinolinium salts

Several new tetrahydroisoquinolinium salts,analogues of atracurium,were designed and synthesized.These compounds were prepared from optically pure tetrahydropapaverine and hex-amethylene diglycidate.     

Asymmetric synthesis of (+)-1-deoxynojirimycin and (+)-castanospermine

Asymmetric total syntheses of (+)-1-deoxynojirimycin (1) and (+)-castanospermine (2) are described. Starting from diene 3, the required absolute stereochemistry is introduced by an asymmetric hydroxylation followed by epoxidation. An intramolecular cyclization of amine 17 gives access to the corresponding tetrasubstituted piperidine 18, which is a precursor to compounds 1 and 2. (+)-Deoxynojirimicyn (1) was obtained in 36% yield over 11 steps from diene 3, while (+)-castanospermine (2) was achieved in 13% after 19 steps from the same starting material.     

Utilizing Vinylcyclopropane Reactivity: Palladium-Catalyzed Asymmetric [5+2] Dipolar Cycloadditions

Vinylcyclopropanes (VCPs) are commonly used in transition-metal-catalyzed cycloadditions, and the utilization of their recently realized reactivities to construct new cyclic architectures is of great significance in modern synthetic chemistry. Herein, a palladium-catalyzed, visible-light-driven, asymmetric [5+2] cycloaddition of VCPs with α-diazoketones is accomplished by switching the reactivity of the Pd-containing dipolar intermediate from an all-carbon 1,3-dipole to an oxo-1,5-dipole. Enantioenriched seven-membered lactones were produced with good reaction efficiencies and selectivities (23 examples, 52–92 % yields with up to 99:1 er and 12.5:1 dr). In addition, computational investigations were performed to rationalize the observed high chemo- and periselectivities.     

手性有机小分子催化的最新进展*

手性有机小分子催化是近年来不对称催化领域发展起来的一个研究热点。手性有机小分子催化具有反应条件温和,环境友好,催化剂易于回收利用等优点,符合绿色化学的要求。本文根据手性有机催化剂活化模式的不同,从烯胺催化、亚胺催化、氢键活化、卡宾催化、相转移催化以及光化学等方面对近年来的有机小分子催化的进展,特别是中国学者的工作做一简要评述。重点通过对不同催化体系下催化剂和反应底物之间立体效应和电子效应的考察,发现控制反应立体选择性以及活化惰性底物的规律,进而设计更加高效的手性有机小分子催化剂,完善和拓展有机小分子催化的不对称合成。     

Asymmetric synthesis of (+)-tetrahydropseudodistomin

An efficient asymmetric synthesis of (+)-tetrahydropseudodistomin is described. The important synthetic features include a Maruoka asymmetric allylation and a Sharpless asymmetric dihydroxylation as key steps for the generation of chirality at C-2, -4, and -5 of the trisubstituted piperidine ring.