Synthesis Of (2,3)-trans-chiral Pyrrolidines Controlled By Protective Groups

In the synthesis of complex compound,the protecting group is widely used to ensure the chemical selectivity to a specific group.Thus,various efficient protecting methods with different functional groups and conditions have been developed and are used for the synthesis of natural products and important compounds.Pyrrolidine moiety with different configurations is embed in many natural products and medicines,and has widely application in polymer materials and spices.Different types of chiral pyrrolidine compounds tend to have different chemical properties.Therefore,it is important to achieve the selective synthesis of chiral multisubstituted pyrrolidine with different configurations through the regulation of protecting groups.Herein,an asymmetric Michael addition/annulation sequence of N-trifluoroacetyl protected aminoacetone and cinnamaldehyde catalyzed by a chiral secondary amine derived from proline was developed,affording a series of pyrrolidine derivatives with 55% to 90% yields.The product was subjected to reduction of the hydroxyl group to give a series of chiral pyrrolidines having a 2,3-trans configuration(yield;39%-70%,ee: 85%-96%).The configuration control has been explained reasonably combined with the X-ray crystal structure of the product.