The structures of podolactones C and D, the first terpenes known to contain a sulphoxide grouping, are shown to be (3) and (4) respectively.EARLIER~ we reported that the bark from a Podocarpus species (cf, P. neriifolius D. Don ex Lamb.) contained two norditerpenoid dilactones, podolactones A (1) and B (2), with plant growth inhibitory activity.Further fractionation of the extract yielded two other compounds of thesame type, podolactones C and D, which have lower inhibitory activity than podolactone A and which are shownto have structures (3) and (4) respectively.Podolactone C (3), m.p. 288-290"(decomp.), has theformula C2,H2,08S from microanalysis.U.V. and i.r.spectra show the presence of the arb-unsaturated a-lactone[Amax (EtOH) 218 nm (E 12,500), Vmax (KBr) 1720 and1645 cm-l] and 7-lactone (vmax 1780 cni-l) groups found inpodolactones A and B, and a hydrogen-bonded hydroxygroup (\jmax 3150 cm-l). In the n.m.r. spectrum (Table) of pound, C2,H2a0,S, m.p. 330" (decomp.), shows in its n.m.r.spectrum the expected downfield shifts of the C-16 protonresonances (from 6 3-39 and 3-76 to 3-70 and 4-48 p.p.m.respectively), the C-17 methyl (from 1-85 to 2-00), and theextra methyl signal (from 2.66 to 3.23, cf. dimethyl sulphone,3.07 in pyridine).The remainder of the spectrum wassimilar to that of the parent compound. The i.r. spectrumof the sulphone shows strong bands, not present in thespectrum of the parent compound, at 1315 and 1140 cm-l,characteristic of sulphones. 2bAttempts to reduce the sulphoxide to a sulphide, to effecta Pummerer rearrangement, or to desulphurize the moleculewere not successful.