The photosensitized oxygenation of petasalbin I gave almost quantitatively a crystalline mixture of two isomeric hydroperoxides, V-a and V-b, both of which were then transformed to the corresponding lactones, VI-a and VI-b, respectively, in good yields. The stereochemistry of these hydroperoxides and lactones has been established by spectral and chemical methods. Furthermore, two natural lactones, III and IV, were prepared by the reduction of the hydroperoxides.

The dye-sensitized oxygenation of furanofukinin, and furanoeremophilane, in methanol gave, quantitatively, crystalline mixtures of two isomeric hydroperoxides each consisting of a pair of 8α-methoxy-12β-hydroperoxy and 8β-methoxy-12α-hydroperoxy derivatives respectively. The hydroperoxides were readily transformed to the corresponding lactones with acetic anhydride-pyridine through dehydration. The stereochemistry of the hydroperoxides and the corresponding lactones has been elucidated by spectral and chemical methods according to a previously outlined generalization. Further, furanofukinin, furanoeremophilane, and 8β-hydroxyeremophilenolide, have been synthesized from petasalbin, fukinone, and an epimeric mixture of 8α- and 8β-methoxy lactones, respectively.

Two prostaglandin synthetase inhibitory anacardic acids were isolated from O. mucronata. The structures of these inhibitors were established by spectroscopic means. Efficient syntheses of these two via directive metallation were reported.

The structures and absolute configurations of five new sesquiterpenic lactones—fukinolide (1), dihydrofukinolide (2), homofukinolide (3), S-fukinolide (4), and fukinanolide (5)—isolated from the flower stalks of Petasites japonicus Maxim. have been established by a combination of spectroscopic and chemical methods, and by correlation with the known fukinone (25).

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