Pregnan

C21H36O2. M,p. 238°C. There are four isomeric pregnane-3,20-diols differing only in the orientation of the hydroxyl groups at positions 3 and 20 and with the 5/ configuration. Only the 3a,20a occurs naturally. It is formed by reduction of progesterone in the liver and is the chief urinary metabolite of it, being... 

Methods for reconstmcting the C-17 side chain from intermediates such as androstendione have been developed. These are used when commercial considerations favor the production of androstanes, but pregnanes are the ultimate goal (25,30). 

AHopregnanolone and similar A-ring-reduced pregnanes potentiate GABA effects at these receptors. These steroids mimic the effects of the benzodiazepines, changing chloride ion conductance and producing sedative and hypnotic behavioral effects (276,277). Neuroactive steroids can be therapeutically useful as anticonvulsants, anxiolytics, or anesthetics (qv) (see also Hypnotics, sedatives, anticonvulsants, and anxiolytics). 

Chemical Analysis. Chemically, the various progestogens belong to one of three classes. Estranes are 19-nortestosterone derivatives (Fig. 1) gonanes are 19-nortestosterone derivatives with a C-13 ethyl group (Fig. 2) and pregnanes are 17-alpha-OH progesterone derivatives similar in stmcture to progesterone itself. 

The pregnanes include megestrol, medroxyprogesterone acetate [71-58-9] C24H34O4 (6), chlormadinone acetate [302-22-7] C23H2QCIO4, and cyproterone acetate [427-51-0], C24H2gC104 (7). 

Bisnorcholanic acid (pregnane-20-carboxylic acid) [28393-20-6] M 332.5, m 214 (a-form), 242 (p-form), 210-211 (y-form), 184 (5-form), 181 (e-form), pKe -5.0. Crystd from EtOH (a-form), or acetic acid (all forms). 

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... 

A solution of 2 g of sodium borohydride in 5 ml of water is added at room temperature to a solution of 1 g of 3a-hydroxy-5jS-pregnane-l 1,20-dione in 15 ml of methanol. Almost immediately, crystals begin to form. After the mixture has been kept overnight, the precipitate is collected with suction to yield 0.8 g of the diol, mp 230-232°. The analytical sample, crystallized once more from aqueous methanol, melts at 231.4-232.6° [a]p 31.2° (acetone). Reported mp 236-238°. 

Refluxing 3a-hydroxy-5)5-pregnane-ll,20-dione in methanol overnight with sodium borohydride gives the 3a,llj5,20jS-triol in 85% yield with mp 233-235°, [ ][) 38.9° (dioxane). 

When 3a,17a-dihydroxy-5jS-pregnane-ll,20-dione is allowed to react at room temperature overnight with sodium borohydride in aqueous methanol, no crystals form and only 5j5-pregnane-3a,l ljS,17a,20j5-tetrol is isolated in good yield. If the reaction is halted at the end of 3 h y the addition of water and extraction with chloroform, it is possible xo obtain a 55% yield of 3a,17a,20jS-trihydroxy-5j5-pregnan-ll-one, mp 218-220°,after recrystallization of the chloroform residue from aqueous methanol. The analytical sample, crystallized once more, has mp 219.0-220.6° [a][, 36° (acetone), reported mp 220° [aJu 38°. 

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