Oxidation of Cage Derivatives of Quinopimaric Acid

The oxidation of cage compounds derived from quinopimaric acid, namely gamma-diketone, oxa-"bird cage," 18-chloro-15-oxa-"bird cage," and 16-sulfanyl-15-oxa-"bird cage," was studied using a number of oxidating agents, including sodium percarbonate in trifluoroacetic acid at 0 degrees C, 36% hydrogen peroxide in acetone at room temperature, and tert-butyl hydroperoxide in the presence of MoCl5 in boiling benzene. It was shown for the first time that the oxidation of diterpene oxa-"bird cages" led to the formation of mixtures of keto lactones (Baeyer-Villiger oxidation products), in which 7,10-dioxo-6-oxaheptacyclo[11.8.0.0(3,8).0(4,12).0(5,11).0(9,13).0(16,21)]heneicosane was the major component.