Stereoselective synthesis of 9α-hydroxylated ecdysteroids

Treatment of ecdysteroids with excess of TBAF in THF was shown to proceed with stereoselective oxidation at the 9α position of the carbon skeleton. The stereochemistry of the products was confirmed by X-ray analysis. Using this method, 9α-hydroxyecdysteroids were obtained in good yield. The results open a route to novel type of natural and modified steroids that are difficult to access otherwise.