Cu/Mn Co-oxidized Cyclization for the Synthesis of Highly Substituted Pyrrole Derivatives from Amino Acid Esters: A Strategy for the Biomimetic Syntheses of Lycogarubin C and Chromopyrrolic Acid

An
effective and concise approach to synthesis of tetrasubstituted
pyrroles from readily available amino acid esters by the promotion
of Cu­(OAc)2 in conjunction with Mn­(OAc)3 has
been developed. This reaction proceeds through multiple dehydrogenations,
deamination, and oxidative cyclization. This oxidized system tolerates
substrates bearing various electron-donating or electron-withdrawing
groups. With this methodology, several key intermediates of natural
products have been effectively prepared, and the total syntheses of
lycogarubin C and chromopyrrolic acid have been completed in high
efficiency.