INTRAMOLECULAR AND INTERMOLECULAR HYDROXYL REACTIVITY DIFFERENCES IN GINKGOLIDES A, B AND C AND THEIR CHEMICAL APPLICATIONS.

An investigation of the chemistry of ginkgolides A, B and C (1) has revealed an unusual interaction between the hydroxyl groups at C(1) and C(10) which activates their deprotonation to give 2 and provides a method for the interconversion of 1C and 1B. The ginkgolide 7-enol system 7 is more stable than the corresponding 7-keto form 6, which is easily made by selective Jones oxidation of ginkgolide C.