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Cortisone: Cortisone, 17a,21-dihydroxypregn-4-en-3,11,20-trione (27.1.26), is also synthesized in various ways from compounds already having the steroid skeleton. One of them is very similar to a method of making hydrocortisone described above, in which it is synthesized from progesterone, which undergoes microbiological oxidation, forming 11a-hydroxyprogesterone (27.1.9). The hydroxyl group of the last is oxidized by chromium(VI) oxide in acetic acid, giving 11-ketoprogesterone (27.1.10). This is reacted with diethyloxalate in the presence of sodium ethoxide, forming the corresponding a-ketoester in the form of a sodium enolate 27.1.11, which undergoes bromination with two equivalents of bromine, giving a dibromoketone 27.1.12. The resulting dibromoke-tone undergoes a Favorskii rearrangement, but the product is not hydrolyzed, and the unsaturated acid is isolated in the form of a methyl ester 27.1.20. Reacting this with pyrrolidine gives a dienamine 27.1.21, which undergoes reduction by lithium aluminum hydride, which results in that, the keto-group on C11 transforms into a hydroxyl group, and the carbmethoxy group to a primary alcohol, forming the compound 27.1.22. Acidic hydrolysis of the product and subsequent acetylation gives an acetate 27.1.23, and the hydroxyl group at C11 in which it is oxidized with chromium(VI) oxide to a ketone, forming the compound 27.1.24. This undergoes a reaction with osmium tetroxide, and the resulting osmate is oxidized by magnesium dioxide in N-methylmorpholine, giving cortisone acetate 27.1.25. Hydrolysis of the acetyl group using sodium bicarbonate leads to the formation of cortisone (27.1.26) [6,9,10].

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