Highly Stereodivergent Synthesis of Chiral C4-Ester-Quaternary Pyrrolidines: A Strategy for the Total Synthesis of Spirotryprostatin A

Abstract

In this work, we disclose two sets of highly diastereo- and enantioselective [3 + 2] cycloadditions of iminoesters with various α-substituted acrylates, especially for sterically hindered and weakly activated α-aryl or alkyl-substituted acrylates and alkenal, alkynal, or unstable aliphatic aldehyde-derived iminoesters, catalyzed by the AgHMDS/DTBM-Segphos or Ag₂O/CA-AA-Amidphos catalytic system, achieving the stereodivergent synthesis of chiral C4-ester-quaternary <i>exo</i>- or <i>endo</i>-pyrrolidines with high yields and excellent diastereo- and enantioselectivities (up to >99:1 dr and >99% ee). More importantly, the gram-scale synthetic <i>exo</i>-adduct displays significant applications in the aspect of realizing the total synthesis of the spirotryprostatin A alkaloid via nine steps in a 36% overall yield.