Chemistry of Saururus cernuus, VI: Three new neolignans.

From the relatively more lipophilic fraction of the extract of Saururus cernuus, seven neolignans were isolated of which three, named (-)-saururin, (-)-saururenin, and (+)-saururinone, are new and belong to the 1,4-diaryl-2,3-dimethylbutane group, with saururinone being a novel ketoneolignan. The remaining four were identified as (-)-austrobailignan 6, another member of the 1,4-diarylbutane group, and (-)-calopiptin, (-)-galbacin, and (+)-zuonin A, all three of which belong to the 2,5-diaryl-3,4-dimethyltetrahydrofuran group. Of these, zuonin A has the rarely seen stereochemistry for the tetrahydrofuran ring: 2/3 cis, 3/4 cis, and 4/5 trans.