作者:Shahab Mortezaei、Noelle R. Catarineu、James W. Canary                                    
                                    
                                        DOI:10.1021/ja302283s
                                    
                                    
                                        日期:2012.5.16
                                    
                                    A redox-reconfigurable catalyst derived from L-methionine and incorporating catalytic urea groups has been synthesized. This copper complex catalyzes the enantioselective addition of diethyl malonate to trans-beta-nitrostyrene. Either enantiomer of the product can be predetermined by selection of the oxidation state of the copper ion. Enantiomeric excesses of up to 72% (S) and 70% (R) were obtained in acetonitrile. The ability of the catalyst to invert enantiomeric preference was reproduced with several different solvents and bases. Facile interconversion between the Cu2+ and Cu+ redox states allowed easy access to both active helical forms of the complex and, therefore, dial-in enantioselectivity.