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Total synthesis of (±)-lundurine B.

A total synthesis of (±)-lundurine B was accomplished. A combination of stereoselective intramolecular cyclopropane formation and aryl amination furnished cyclopropane-fused indoline stereoselectively. Ring-closing metathesis (RCM) of siloxy diene and intramolecular aminoacetal formation followed by bridgehead vinylation of an anti-Bredt iminium cation led to the construction of six- and seven-membered rings with a quaternary carbon center. After the formation of dihydropyrrole by RCM, the Boc-protecting group of indoline was converted into the corresponding methyl carbamate via silyl carbamate to complete the total synthesis of (±)-lundurine B. The characteristic rearrangement of the cyclopropane-fused indoline skeleton is also described.