Pregnenolone, acetate

Pregnenolone acetate (111) is brominated to give the intermediate 7-bromo compound (112). This is dehydrobrominated in collidine to yield the title... 

The addition of HF to the 5,6-double bond in 3-hydroxy-A -steroids has been investigated intensively. Bowers et al. prepared the 5oc-fluoro derivative (32) from pregnenolone acetate (31) in 10 % yield using methylene dichloride-THF as solvent at 0°. Pregnenolone itself is converted in 30%... 

Overall yields of 37% from pregnenolone acetate to 19-norprogesterone and of 43% from 3 -acetoxy-5a-chloro-6l5-hydroxy androstan-17-one to A io)-19-norandrostene-3,17-dioneii have been reported using 6)5,19-ethers as key intermediates. 

Hydrolysis of the acetate (71) followed by Oppenauer oxidation gives B-norcholest-4-en-3-one in high yield. An analogous reaction sequence can be used to prepare B-norprogesterone and derivatives of B-nortestosterone from pregnenolone acetate and dehydroepiandrosterone acetate, respectively."" ... 

Ozonization of A -steroids usually gives complex mixtures (however, see ref. 48). Ozonolysis became a practical step in the general synthesis of B-norsteroids with the discovery that added methanol" (or formaldehyde ) improves yields significantly. Thus, Tanabe and Morisawa prepared 5/ -hydroxy-6/ -formyl-B-norsteroids (74) from cholesterol acetate, dehydroepiandrosterone acetate and pregnenolone acetate in overall yields of 64-74% by the reaction sequence represented below. 

Allylic bromination of pregnenolone acetate with dibromodi-methylhydantoin affords the 7-bromo compound (155) of undefined stereochemistry. Dehydrobromination by means of collidine followed by saponification affords the 5,7 endocyclic cis,cis-diene, 156. This compound contains the same chromophore as ergosterol, a steroid used as a vitamin D precursor. The latter displays a complex series of photochemical reactions among the known products is lumisterol, in which the stereochemistry at both C9 and Cio is inverted. Indeed, irradiation of 156 proceeds to give just such a product (158). This reaction can be rationalized by... 

Medroxyprogesterone Acetate Megestrol Acetate Melengestrol Acetate Norethindrone Pregnenolone Acetate Progesterone... 

Pregnenolone acetate reduction with lithium aluminum tn t butoxy hydride, 46, 58... 

Potassium ferricyanide in oxidative decarboxylation, 40, 86 Potassium permanganate for oxidation of (trialkylmethyl)amines to tri-alkylnitromethanes, 43,87 Pregnenolone acetate, conversion to 3/3-acetoxyetienic acid, 42, 5 Propane, 2,2-dibotoxy-, 42,1 Propargylsuccinic anhydride, by-product in addition of maleic anhydride to allcne, 43, 27... 

The first crop of the product contains only a trace of the 20 -epimer. The main portion of this compound is found in the mother liquor. Use of the material of a second crop for the subsequent steps is not recommended. The residue of the mother liquor can, however, be reoxidized to pregnenolone acetate by the method described in step C. By crystallization of the oxidation product of the mother liquor residue from methanol, 13-14 g. of pure pregnenolone acetate can be recovered. 

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