A practical synthesis of optically active δ-nitro-α-ketoesters and 4-cyclohexyl-proline catalyzed by chiral squarnides

作者：Liu, Ri-long; Yan, Yun-yun; Zhang, Ting; Zhang, Xue-jing; Yan, Ming^*

来源：Tetrahedron: Asymmetry , 2015, 26(24): 1416-1422.

DOI：10.1016/j.tetasy.2015.10.009

• ASYMMETRIC MICHAEL ADDITION
• ORGANOCATALYTIC CONJUGATE ADDITION
• ENANTIOSELECTIVE SYNTHESIS
• ESTERS
• NITROOLEFINS
• NITROACETATE
• ACID

Inexpensive and readily available squamides derived from 9-amino-9-deoxyepiquinine or 9-amino-9-deoxyepiquinidine were found to be superior catalysts for the asymmetric conjugate additions of t-butyl nitroacetate to beta,gamma-unsaturated-alpha-ketoesters. After the subsequent decarboxylation with silica gel, a variety of delta-nitro-alpha-ketoesters were obtained in good yields and with excellent enantioselectivities. The products were further transformed into ethyl 4-aryl-prolinate via a cascade nitro reduction and amination. A new synthesis of (2S,4S)-4-cyclohexyl-proline was also developed. A practical synthesis of optically active delta-nitro-alpha-ketoesters and 4-aryl-proline derivatives is described.

• 出版日期2015-12-31
• 单位宝鸡文理学院; 中山大学