Organocatalysis in Conjugate Amine Additions. Synthesis of β-Amino Acid Derivatives
作者:Mukund P. Sibi、Kennosuke Itoh
DOI:10.1021/ja071739c
日期:2007.7.1
Conjugateaddition of O-protected hydroxylamines to pyrazole-derived enoates proceeds with high efficiency and enantioselectivity when chiral thioureas are used as activators. A wide variety of substrates undergo conjugate amine addition providing access to enantioenriched β-aminoacidderivatives. Structural requirements for the optimal thiourea catalyst have been established, and the results suggest
Temperature dependent reversal of stereochemistry in enantioselective conjugate amine additions
作者:Mukund P Sibi、Uma Gorikunti、Mei Liu
DOI:10.1016/s0040-4020(02)00988-2
日期:2002.10
Enoates derived from 4,4-disubstituted-2-oxazolidinones undergo enantioselective conjugate amineaddition when mediated by a chiral Lewis acid derived from magnesium bromide and a bisoxazoline. The face selectivity in these amineadditions is temperature dependent. They show an unusual reversal at two different temperatures.
The first intermolecular asymmetric Michael addition of nitrogen-nucleophiles to alpha,beta-unsaturated carboxylic acids was achieved through a new type of arylboronic acid equipped with chiral aminothiourea. The use of BnONH2 as a nucleophile gives a range of enantioenriched beta-(benzyloxy)amino acid derivatives in good yields and with high enantioselectivity (up to 90% yield, 97% enantiomeric excess