Hydroxyprogesterone: Hydroxyprogesterone, 17a-hydroxypregn-4-en-3,20-dione (28.3.6), is synthesized from dehydropregnenolon (28.3.2). Dehydropregnenolon itself is made by successive decomposition and oxidation of the side spiroketal group of diosgenin—the agly-cone of one of the saponins of plant origin isolated from Discorea. The double bond at C16-C17 or dehydropregnenolon is oxidized by hydrogen peroxide in the presence of a base to give an epoxide (28.3.3). Interaction of the resulting epoxide with hydrogen bromide in acetic acid forms a bromohydrin (28.3.4). The hydroxyl group of C3 of the steroid system is formylated by formic acid, and reduction by hydrogen over a palladium catalyst removes the bromine atom at C16, forming the product (28.3.5). The hydroxyl group at C17 of this product is acylated by acetic acid anhydride and then the formyl group at C3 is oxidized by aluminum isopropylate in the presence of cyclohexanone, during which simultaneous isomerization takes place at the double bond, isomerizes from C5-C6 to position C4-C5, forming the desired hydroprogesterone ester, in the given case an acetate (28.3.6), in which form it is used in medical practice [64,65]. Other alternative ways of synthesis have been proposed [66-72].
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