The Photosensitized Oxygenation of Furanoeremophilanes. I. The Isomeric Hydroperoxides from Petasalbin and Their Transformations to Lactones

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...