Total Synthesis of Lapidilectine B Enabled by Manganese(III)-Mediated Oxidative Cyclization of Indoles.

A novel manganese(III)-mediated oxidative cyclization of readily accessible 1,2,3-trisubstituted indoles is described. This unprecedented method enabled the efficient construction of a complex polycyclic scaffold bearing a spiro-indoline motif and a lactone moiety in one step. Its synthetic utility was demonstrated in the total synthesis of lapidilectine B (in 18 steps) by employing a strategic regioselective ring-expansion and a silver-promoted allenic amine cyclization as the additional key elements.