Madangamine A is a novel pentacyclic alkaloid that was isolated from the marine sponge Xestospongia ingens by Andersen in 1994. Soon after, new constituents of this alkaloid type, madangamines B–E, were isolated from the same organism. The first successful attempt at synthesizing the eleven-membered ring of madangamine alkaloids is described. The synthesis involves intramolecular N,O-acetalization of a cyclohexanone derivative, cross-coupling reaction with (Z)-vinylstannane, and intramolecular reductive amination for elaboration of the eleven-membered macrocycle.