5/3-Pregnane-3,11,20-trione

A solution of 7.2 g of sodium borohydride (analyzing at 87 % purity) in 300 ml of pyridine is added dropwise, with vigorous stirring, over 7 hr to a solution of 50 g of pregnane-3,11,20-trione in 100 ml of pyridine and 18 ml of water. The temperature is kept at 18-20°. The stirring at this temperature is continued for another 2 hr, after which the reaction mixture is poured slowly into dilute hydrochloric acid (575 ml of cone hydrochloric acid in 5.2 liters of water) and the stirring continued for 1 hr. The precipitate is filtered, washed with... 

Acetoxy-17a-hydroxy-5a-pregnane-3,l 1,20-trione (40) is brominated in acetic acid under equilibrating conditions to give a solution of the 2a,4a-di-bromo compound (41). This is reduced by chromous chloride without further treatment, to the 4a-bromo compound (42). The recrystallized bromo compound (42) is then dehydrobrominated via the semicarbazone (43) which is converted without isolation into cortisone acetate (44) by treatment with pyruvic acid ... 

Similarly, treatment of 5a,6a-oxido-3,20-bisethylenedioxy-6j9-methyl-pregnan-17a-ol (107) with 72% perchloric acid in acetone gives 17a-hydroxy-6l5-methyl-10(5 6)fl >e<3-pregnane-3,5,20-trione (108b). 

Several routes to 2,3-diketones have been reported. The most practical and general method is that of Ruzicka, Plattner and Furrer as adapted by Nace and Nelander for synthesis of the diosphenol corresponding to 5a-pregnane-2,3,20-trione (44) starting from 5a-pregnane-3,20-dione (40). The overall yield of diosphenol (44) by this route is 62% based on... 

ChIoro-5a-cholestane, 332 3/3-Chlorocholest-5-ene, 453 4-Chlorocyclohexanone, 72 3 /3-Chloro-5,6a-difluoro-5a-cholestane, 453 4-Chloro-17a-hydroxy-5/3-pregnane-3,11, 20-trione, 86 Chloroiridic acid, 101 4-Chloro-2-phenylquinazoline, 450 Choice of protecting groups, 375 A/B-cfs-cholanic acid, 228 Cholan-12-one, 36 Cholesta-3,5-diene, 207, 331, 336... 

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