Enantioselective Synthesis of Planar Chiral Organonitrogen Cycles
摘要:
Enantioselective synthesis of a planar chiral organonitrogen cycle has been newly developed based on the unprecedented prochiral face-selective cyclization of achiral linear precursors by an appropriate chiral promoter.
Both enantiomers of kainic acid have been synthesized from enantioenriched planar chiral cyclic amide 2a. The C3 and C4 stereocenters in the pyrrolidine ring were constructed by transannular Cope rearrangement of 2a, and the carboxyl group at the C2 position was introduced through lithiation followed by a carboxylation in the presence of an external chiral ligand.