21-Hydroxypregna-1,4,9(11),16-tetraene-3,20-dione 21-acetate is a steroidal compound with a complex tetracyclic structure featuring a 1,4,9(11),16-tetraene system and a 21-acetate group. It is a key synthetic intermediate in the production of steroidal drugs, particularly glucocorticoids and anti-inflammatory agents. This compound serves as a crucial precursor in the multi-step synthesis of important corticosteroids such as prednisolone and its derivatives. The specific unsaturation pattern and the presence of the 21-acetate group make it a strategic chiral building block for introducing further functional modifications required for biological activity. Its primary industrial application is within pharmaceutical manufacturing processes. Handling requires standard precautions for potent organic intermediates. It is typically used under controlled conditions in research and development laboratories and large-scale API production facilities focusing on steroidal therapeutics.