Total Synthesis of (−)-Lepadiformine A viaRadical Translocation–Cyclization Reaction

Total synthesis of (−)-lepadiformine A featuring construction of the 1-azaspiro[4.5]­decane skeleton by a highly diastereoselective radical translocation–cyclization reaction of a γ-lactam derivative bearing a chiral butenolide moiety is described. The enantioselective construction of butenolide is conducted via Krische’s catalytic asymmetric allylation protocol. After the radical translocation–cyclization reaction, a hydroxymethyl group at the C-13 position was stereoselectively introduced by a one-pot partial reduction–allylation protocol of the unprotected lactam derivative. Finally, the total synthesis is completed by formation of a C ring.