Transformation of 9α,14α-epoxy-14-deoxy-20-hydroxyecdysone diacetonide into 25-hydroxydachryhainansterone

9α,14α-Epoxy-14-deoxy-20-hydroxyecdysone diacetonide on treatment with NaBH₄ undergoes reduction of 6-keto group and cleavage of allylic oxetane ring, the 6-keto reduction is accompanied by β→α epimerization of the adjacent HC⁵ centre. Subsequent re-oxidation of the 6-CHOH fragment into ketone with pyridinium chlorochromate and acidic deprotection affords 25-hydroxydachryhainansterone possessing β-HC⁵ configuration due to the re-epimerisation at this centre.