An Enantioselective Strategy for the Synthesis of (S)-Tylophorine via One-Pot Intramolecular Schmidt/Bischler–Napieralski/Imine-Reduction Cascade Sequence

A novel enantioselective strategy for the total synthesis of (S)-tylophorine was developed in an overall yield of 48% with more than 99% ee from readily avaliable azido acid and phenanthryl alcohol. This route features an Evans stereoselective alkylation and an unprecedented one-pot intramolecular Schmidt/Bischler-Napieralski/imine-reduction cascade sequence, in which three new bonds and two rings formed in 84% yield. The intramolecular Schmidt rearrangement of the azido aldehyde was proved to be racemization-free.