The invention provides novel compounds and methods to carry out organocatalytic Michael additions of aldehydes to nitroethylene catalyzed by a proline derivative to provide α-substituted-γ-nitroaldehydes. The reaction can be rendered enantioselective when a chiral pyrrolidine catalyst is used, allowing for Michael adducts in nearly optically pure form (e.g., 96-99% e.e.). The Michael adducts can bear a single substituent or dual substituents adjacent to the carbonyl. The Michael adducts can be efficiently converted to protected γ
2
-amino acids, which are essential for systematic conformational studies of γ-peptide foldamers.
The invention provides novel compounds and methods to carry out organocatalytic Michael additions of aldehydes to nitroethylene catalyzed by a proline derivative to provide α-substituted-γ-nitroaldehydes. The reaction can be rendered enantioselective when a chiral pyrrolidine catalyst is used, allowing for Michael adducts in nearly optically pure form (e.g., 96-99% e.e.). The Michael adducts can bear a single substituent or dual substituents adjacent to the carbonyl. The Michael adducts can be efficiently converted to protected γ2-amino acids, which are essential for systematic conformational studies of γ-peptide foldamers.
Enantioselective Organocatalytic Michael Addition of Aldehydes to Nitroethylene: Efficient Access to γ<sup>2</sup>-Amino Acids
作者:Yonggui Chi、Li Guo、Nathan A. Kopf、Samuel H. Gellman
DOI:10.1021/ja800345r
日期:2008.4.1
EnantioselectiveorganocatalyticMichaeladdition of aldehydes to nitroethylene catalyzed by (S)-diphenylprolinol silyl ether provides beta-substituted-delta-nitroalcohols in nearly optically pure form (96-99% ee). The Michael adducts bear a single substituent adjacent to the carbonyl and can be efficiently converted to protected gamma2-amino acids, which are essential for the systematic conformational