Enantioselective Total Synthesis of Beraprost Using Organocatalyst.

A convergent and enantioselective total synthesis of the most active isomer of beraprost was achieved in 17 pots. A unique tricyclic core in beraprost was synthesized efficiently by utilizing the asymmetric organocatalyst-mediated formal [3 + 2] cycloaddition reaction of succinaldehyde with nitroalkene as a key step. The synthesis of the optically active Horner-Wadsworth-Emmons reagent for the construction of the ω-side chain was also established by means of the enantioselective Michael reaction of crotonaldehyde with nitromethane catalyzed by the organocatalyst developed by our group.