两种富含α-氨基异丁酸(Aib)残基的短五肽已被证明可作为亲核试剂与硝基烯烃的共轭加成的对映选择性有机催化剂。 L -丙氨酸封端的肽 (Aib) 4 ( L -Ala)NH t Bu 既没有功能化侧链,也没有高度设计的反应位点,使用暴露的 N 末端伯胺和主链的酰胺键来介导催化作用。通过晶体学观察到该肽折叠成 3× 10螺旋结构。折叠成螺旋将 C 末端的手性丙氨酸残基的构象偏好传递给 N 末端的伯胺,相距 0.9 nm。 3 ·10螺旋产生的手性环境和确定的形状使胺位点靠近两个暴露的酰胺 NH。反应范围研究表明,胺充当布朗斯台德碱,并且需要暴露于溶剂的螺旋 NH 基团(显示与 β-硝基苯乙烯的结合较弱)才能获得对映体过量。用D-苯丙氨酸替换L-丙氨酸得到 (Aib) 4 ( D -Phe)NH t Bu,这是一种肽,现在以相反的对映选择性催化基准反应。这些研究表明非手性残基如何通过促进折叠在肽的对映选择性催化中发挥关键作用。
Novel chiral hydrogen bond donor catalysts based on a 4,5-diaminoxanthene scaffold: application to enantioselective conjugate addition of 1,3-dicarbonyl compounds to nitroalkenes
Novelchiral hydrogen bond donor catalysts based on a 4,5-diamino-9,9′-dimethylxanthene skeleton were designed and synthesized. Among the phenylurea-amide hybrid molecules prepared from various natural/unnatural chiral amino acids, the phenylalanine-derived catalyst, and the proline-derived catalyst were successfully applied to enantioselective conjugate addition of 1,3-dicarbonyl compounds to nitroalkenes
Ephedrine- and Pseudoephedrine-Derived Thioureas in Asymmetric Michael Additions of Keto Esters and Diketones to Nitroalkenes
作者:Carsten Bolm、Angelika Flock、Anke Krebs
DOI:10.1055/s-0029-1219582
日期:2010.5
Ephedrine-derived bifunctional thioureas have been synthesized and applied as organocatalysts in Michael additions of 1,3-dicarbonyl compounds to nitroalkenes.
Chiral Squaramide Derivatives are Excellent Hydrogen Bond Donor Catalysts
作者:Jeremiah P. Malerich、Koji Hagihara、Viresh H. Rawal
DOI:10.1021/ja805693p
日期:2008.11.5
dominant platform for hydrogen bond promoted asymmetric catalysts. A large number of reactions, reported in scores of publications, have been successfully promoted by chiral thioureas. The present paper reports the use of squaramides as a highly effective new scaffold for the development of chiral hydrogen bond donor catalysts. Squaramide catalysts are very simple to prepare. The (-)-cinchonine modified
thiourea moiety and an amino group on a chiral scaffold. Among them, thiourea 1e bearing 3,5-bis(trifluoromethyl)benzene and dimethylamino groups was revealed to be highly efficient for the asymmetric Michael reaction of 1,3-dicarbonyl compounds to nitroolefins. Furthermore, we have developed a new syntheticroute for (R)-(-)-baclofen and a chiralquaternarycarboncenter with high enantioselectivity by Michael
我们在手性支架上合成了一类带有硫脲部分和氨基的新型双功能催化剂。其中,带有 3,5-双(三氟甲基)苯和二甲氨基的硫脲 1e 被证明对于 1,3-二羰基化合物到硝基烯烃的不对称迈克尔反应非常有效。此外,我们通过迈克尔反应开发了 (R)-(-)-巴氯芬和具有高对映选择性的手性季碳中心的新合成路线。在这些反应中,我们假设催化剂的硫脲部分和氨基分别活化硝基烯烃和 1,3-二羰基化合物,以提供具有高对映选择性和非对映选择性的迈克尔加合物。
Bottom-Up Synthesis of Supported Thioureas and Their Use in Enantioselective Solvent-Free Aza-Henry and Michael Additions
作者:José M. Andrés、Noelia de La Cruz、María Valle、Rafael Pedrosa
DOI:10.1002/cplu.201500476
日期:2016.1
Two sets of supported chiral thioureas, which differ in the length of the tether that connects the chiral appendage to the polymer structure and the effective functionalization, have been prepared by copolymerization of styrene, novel styryl thioureas derived from l-valine, and divinylbenzene. The efficiency of these polymeric thioureas has been tested in two different enantioselective transformations