Daphnipaxianines A–D, Alkaloids from Daphniphyllum paxianum

Four new Daphniphyllum alkaloids, daphnipaxianines A–D (1–4), along with six known ones, have been isolated from the leaves and fruits of Daphniphyllum paxianum. Daphnipaxianines A and B (1, 2), a pair of epimers differing at C-10, are the first caliciphylline A type Daphniphyllum alkaloids with a Δ⁹⁽¹⁵⁾-unsaturated cyclic ketone unit, and daphnipaxianine D (4) is the first yuzurine-type Daphniphyllum alkaloid containing a hexacyclic ring system. The structures of these alkaloids were characterized by spectroscopic methods, especially 2D NMR techniques. A single-crystal X-ray diffraction analysis was used to confirm the structure of 1.