Another way of making cortisone is from dihydrocortisone acetate. This undergoes monobromination by bromine, giving the 4-bromo derivative of dihydrocortisone acetate (27.1.27). This is reacted with semicarbazide, which results in removal of hydrobromic acid and simultaneously making the semicarbazone at the keto-group on C3, forming the product 27.1.28. Next, 21-O-acetylcortizone (27.1.29) is isolated from semicarbazone using pyruvic acid. Hydrolysis of the acetyl group using potassium bicarbonate gives the desired cortisone (27.1.26) [11-13].
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