Octahydropiericidin A (HPA) was degraded to C11-, C12- and C14-dioic and C13-hydroxy acids, via C18-keto acid, to which structures XI, X, VIII and VII were proposed respectively through analyses of their NMR and mass spectra. Consideration of these results together with the NMR spectrum of piericidin A (PA) and other chemical evidences led to assign structures IIa and IVa to PA and HPA, respectively.