Organocatalyzed Asymmetric Formal [3+2] Cycloaddition between Cyclic Nitrones and Meldrum's Acid for the Formal Total Synthesis of (-)-Crispine A.

We report herein the formal total synthesis of crispine A. The key feature of our synthetic route is an asymmetric formal [3+2] cycloaddition between cyclic nitrones and Meldrum's acid using a quinine-derived chiral amine-urea. The cycloaddition provided an optically active isoxazolidinone, which was successfully converted to a common precursor of crispine A.