Background: Halogenated corticosteroids are widely used in medicine, and the global
need of these steroidal APIs is estimated to be 40 – 70 tons, annually. Vietnam currently imports
the pharmaceutical compounds up to 90%, in particular 100% of steroidal drugs. Currently,
industrial production is based on the chemical syntheses of corticosteroids from either 16-
dehydropregnenolone acetate (obtained from diosgenin) or androstenedione (obtained from
phytosterol). The development of shorter synthetic schemes and more economically feasible
technologies is of great significance. Introduction of 1(2)-double bond at the final stages of the
corticosteroids synthesis results inpoor yield. 21-Acetoxypregna-1,4,9(11),16-tetraene-3,20-dione
(tetraene acetate) is a key intermediate in the synthesis of highly active halogenated corticosteroids
such as dexamethasone and other halogenated corticosteroids. 21-acetoxypregna-1,4,9(11),16-
tetraene-3,20-dione is a key intermediate in the synthesis of dexamethasone from the readily
available and cheap 9α-hydroxyandrost-4-ene-3,17-dione.
Objective: The purpose of this study was the development of an efficient and shorter procedure for
the synthesis of 21-acetoxypregna-1,4,9(11),16-tetraene-3,20-dione from 9α-hydroxyandrostenedione,
which is a product of a bio-oxidative degradation of the side chain of phytosterols.
Methods: Pregnane side chain was constructed using cyanohydrin method. For 1(2)-
dehydrogenation, selene dioxide was applied for the introduction of Δ1(2)-double bond. Other
stages of the synthesis were epimerization, Stork’s iodination procedure and dehydration.
Result: 21-Acetoxypregna-1,4,9(11),16-tetraene-3,20-dione was prepared from 9α-
hydroxyandrostenedione in yield more than 46%.
Conclusion: An efficient and practically feasible procedure for the synthesis of 21-acetoxypregna-
1,4,9(11),16-tetraene-3,20-dione from 9α-hydroxyandrostenedione, a key intermediate for the
synthesis of 9-haloidated corticoids, has been developed. The procedure can be applied for the
production of value-added 9-haloidated corticoids.