Asymmetric Aza-Mannich Addition of Oxazolones to <i>N</i>-Tosyl Aldimines: Synthesis of Chiral α-Disubstituted α,β-Diamino Acids
作者:Xiaodong Liu、Leijiao Deng、Xianxing Jiang、Wenjin Yan、Chunliang Liu、Rui Wang
DOI:10.1021/ol902916s
日期:2010.2.19
readily prepared cinchona alkaloid ligand and affords a series of valuable α-disubstituted α,β-diamino acid derivatives with excellent enantioselectivities (up to 97% ee) and diastereoselectivities (up to >30:1 dr). The adducts can be transformed into the corresponding protected chiral α-disubstituted α,β-diamino acids by a one-pot hydrolyzed reaction smoothly.
The combination of a chiral phosphate anion with a silver ion has been demonstrated as a powerful and synergistic ion pair catalyst for the aza-Mannich reaction. A series of valuable quaternary alpha,beta-diamino acid derivatives was obtained in high yield, and with excellent diastereo- (up to 25:1 dr) and enantioselectivity (up to 99% ee). The adducts can be smoothly transformed into the corresponding protected chiral quaternary alpha,beta-diamino acids by a one-pot hydrolysis reaction.