New picrotoxane terpenoids, austrobuxusin A-D, from the Australian endemic plant Austrobuxus swanii

Four new picrotoxane terpenoids, austrobuxusin A–D (1–4), were isolated from the Australian endemic plant Austrobuxus swanii. Their structures were fully characterized by 1D- and 2D-NMR and MS data. The relative configurations of compounds (1–4) were assigned by phase-sensitive ROESY experiment. The absolute configuration of austrobuxusin A (1) was determined by the comparison of experimental and DFT-calculated CD spectra. This is the first report of picrotoxane terpenoids from the Australian plant Austrobuxus swanii.