A step-economic and one-pot access to chiral C<sup>α</sup>-tetrasubstituted α-amino acid derivatives <i>via</i> a bicyclic imidazole-catalyzed direct enantioselective <i>C</i>-acylation
Cα-Tetrasubstituted α-amino acids are ubiquitous and unique structural units in bioactive natural products and pharmaceutical compounds. The asymmetric synthesis of these molecules has attracted a lot of attention, but a more efficient method is still greatly desired. Here we describe the first sequential four-step acylation reaction for the efficientsynthesis of chiral Cα-tetrasubstituted α-amino acid derivatives
Chiral Bicycle Imidazole Nucleophilic Catalysts: Rational Design, Facile Synthesis, and Successful Application in Asymmetric Steglich Rearrangement
作者:Zhenfeng Zhang、Fang Xie、Jia Jia、Wanbin Zhang
DOI:10.1021/ja109069k
日期:2010.11.17
A new type of chiral bicycle imidazole nucleophilic catalyst was rationally designed, facilely synthesized, and successfully applied in an asymmetric Steglich rearrangement with good to excellent yield and enantioselectivity at ambient temperature. Moreover, it can be easily recycled with almost no reduction of catalytic efficiency. This is the first example for the successful chiral imidazole nucleophilic
Enantioselective TADMAP-Catalyzed Carboxyl Migration Reactions for the Synthesis of Stereogenic Quaternary Carbon
作者:Scott A. Shaw、Pedro Aleman、Justin Christy、Jeff W. Kampf、Porino Va、Edwin Vedejs
DOI:10.1021/ja056150x
日期:2006.1.1
efficient and are used to prepare chiral lactams (23) and lactones (30) containing a quaternary asymmetric carbon. TADMAP-catalyzed carboxyl migrations in the indole series are relatively slow and proceed with inconsistent enantioselectivity. Modeling studies (B3LYP/6-31G*) have been used in qualitative correlations of catalyst conformation, reactivity, and enantioselectivity.
Helicallychiralpoly(quinoxaline-2,3-diyl)s bearing 4-aminopyrid-3-yl pendants were synthesized as new helical-polymer-based chiral nucleophilic organocatalysts. The obtained chiral nucleophilic polymer catalysts exhibited high catalytic activity, enantioselectivity, and reusability in asymmetric Steglich rearrangement of oxazolyl carbonate to C-carboxyazlactone. The polyquinoxaline-based, helically
Enantioselective Synthesis of 4-(Dimethylamino)pyridines through a Chemical Oxidation-Enzymatic Reduction Sequence. Application in Asymmetric Catalysis
Enantiomerically pure 4-(dimethylamino)-3-(1-hydroxyalkyl)pyridines and 4-(dimethylamino)-3-[hydroxy(phenyl)methyl]pyridine have been prepared through efficient chemoenzymatic routes. For this purpose different lipases and oxidoreductases have been tested in the preparation of optically active 4-chloro derivatives and baker’s yeast was found to be an excellent catalyst for the bioreductions of the