Cis-clerodane diterpene lactones from Amphiachyris dracunculoides. 3

Five cis-clerodane lactones, amphiacrolides J (1), K (2), L (3), M (4), and N (5), were isolated from the aerial parts of the composite Amphiachyris dracunculoides. The first four are new compounds, and the fifth was previously reported from another source. All compounds were assigned stereochemical structures based upon spectral and chemical data, including high-field 1D and 2D NMR for complete assignment of 1H- and 13C-NMR spectra. Amphiacrolide N (5) was converted to amphiacrolide J (1) by treatment with MeOH and TFA, and amphiacrolide L (3) was prepared from amphiacrolide B (9) by CrO3 oxidation to ketone 10 followed by its reduction with NaBH4.