Hydroxylation and epimerization of ecdysteroids in alkaline media: Stereoselective synthesis of 9α-hydroxy-5α-ecdysteroids

• In NaOH–MeOH ecdysteroids undergo epimerization and autoxydation.
• The new 9α-hydroxy-5α-ecdysteroids are synthesized in alkaline media.
• 5α-Epimer of the natural ecdysteroid 9α-hydroxyecdysterone is synthesized.
• The hydrogenation of 9α-hydroxy-5α-ecdysteroids leads to the 7,8 α-dihydroderivatives.

Autoxidation of diacetonides of 20-hydroxyecdysone and ponasterone A under treatment with excess of NaOH in methanol leads to the formation of 9α-hydroxy-5α-ecdysteroids previously not described. Their structures have been determined by detailed NMR analysis. Catalytic hydrogenation (Pd-C, MeOH–MeONa) of hydroxylated ecdysteroids affords the 7,8α-dihydro-9α-hydroxy-5α-ecdysteroids.