A sesquiterpenic keto-alcohol, cyperolone, C_<15>H_<24>O_2, m.p. 41-42° (monohydrate),[α]_D+31.4°, of a novel skeleton has been isolated from nutgrass (Cyperus rotundus Linne) of Japanese origin and shown to have the stereostructure I. The IR and NMR spectra showed the presence of a secondary hydroxyl, an acetyl, an isopropenyl, and a tertiary methyl group. On hydrogenation, I gave the saturated dihydro-derivative (II). Oxidation of I and II afforded the cyclopentanones (V & VI), respectively. LiAlH_4 reduction of I formed the diol (VII) whose NMR spectrum indicated the acetyl bearing carbon in I to be quarternary. Alkali treatment of VI gave the monoketone (XII) which was synthesized from the known 14-noreudesmanone (IX). β-Configuration of the C-3 hydroxyl was deduced by application of the benzoate rule. β-Configuration of the C-5 acetyl was established by examination of the NMR spectra of I, II, and their acetates (III & IV) and by the positive Cotton curve of the derived ketol acetate (XIV). The cis-relationship of the C-3 and C-5 substituents was confirmed by the presence of an intermolecular hydrogen bond in VII. (+)-α-Cyperone (XV) was reduced to give α-cyperol (XVI) which was oxidized to the epoxy-ketone (VIII) via the epoxy-alcohol (XVII). The epoxide (XVIII) was isomerized with BF_3 to afford the dione (V) which on reduction gave the diol (VII). Partial acetylation of VII followed by oxidation yielded cyperolone acetate (III) which was hydrolyzed to furnish the natural cyperolone (I).
