Confirmation of the Revised Structure of Samoquasine A and a Proposed Structural Revision of Cherimoline.

The identity of the natural product samoquasine A has remained obscure since its isolation from custard apple seeds in 2000. One of the proposed structures, benzo[ f]phthalazin-4(3 H)-one, was prepared in two steps by regioselective ortho-lithiation/formylation of N, N-diisopropyl-2-naphthylamide, followed by cyclization with hydrazine, but was shown to be different from the natural product. Perlolidine, another candidate structure, was synthesized by a novel route involving a β-selective Heck reaction of butyl vinyl ether.