The Alkaloids of Ormosiasemicastrata: (−)-Ormosanine, (±)-Piptanthine, (−)-18-Epiormosanine, and (−)-Ormocastrine

The alkaloids of Ormosiasemicastrata have been shown to be (−)-ormosanine, (±)-piptanthine, (−)-18-epiormosanine, and (−)-ormocastrine. The structure and relative configuration shown in 1 have been assigned to ormocastrine on the basis of its 220 MHz n.m.r. spectrum and its conversion to ormosanine, among other products, on hydrogenation.