4/3-Bromo-3-keto-5/3-steroids

Reduction of a 16a-bromo-17-ketone (but not the 16 -epimer) is a little less stereospecific than reduction of the 17-keto compound. When a 2a-bromo-3-keto steroid is reduced, at least 78 % of the 3/ -alcohol is obtained. 

Deuteration at C-9 by Treatment of a 9a-Bromo-11 -keto Steroid with Zinc in Acetic Acid-OD... 

Deuteration at C-9 by treatment of a 9a-bromo-ll-keto steroid with zinc in acetic acid-OD, 204... 

Careful investigation of the bromination reaction of 3 keto steroids, which leads ultimately to 2,4-dibromo derivatives (see, for example, S-2-5-3), revealed that the sequence starts with the formation of a 2a bromo derivative, a futher demonstration of the preferred enolization of the carbonyl group toward the 2 position. 

Bromine addition (Bfj or NBS) to A -S-keto-steroids afforded exclusively diaxial bromo-derivatives (6/5, 7a), which were converted with base into the 4-bromo-A " -3-keto-analogues. °... 

Several steroidal spiro-lactones have been prepared by treatment of a 17-keto-steroid, such as 3jS-acetoxyandrost-5-en-17-one (212), in a Reformatsky reaction with a bromo-ester, which gave an isomeric pair of 17-spiro-lactones, such as (213). Similar results have been obtained in the oestratriene series. 

Dehydrohalogenation. French chemists have utilized this salt for dehydro-brominations, particularly of 4-bromo- and 2,4-dibromo-3-keto steroids. Reactions were conducted in DMF or acetonitrile. 

On the other hand, the slightly different bromo keto dienyne 218 was converted to the unexpected pentacyclic non-steroidal system 222. In this case, 5-exo-trig cyclization of 219 gives 220 and its 3-exo-trig cyclization produces the cyclopropane 221 [63]. 

Keto- from 2-bromo-3-keto-steroids s. 19, 102 Hydrogen peroxide... 

In general, they found that substitution of an a-bromo-group results in a rise in the C=0 frequency of about 20cm . Thus non-conjugated 3-keto-steroids absorb at 1719—1715 cm , whereas... 

Hydroxy-ll-keto- from lla-bromo-12-keto-steroids... 

Addition of dimethylsulfoxonium methylide to the a-face of A -20-ketones, A -5a-H-ketones and A " -3-ketones results in the formation of the corresponding 16a,17a-methylene (1), la,2a-methylene-5a-H (2) and la,2a-methylene-A" steroids (3), respectively. Smooth reaction is also observed in the presence of 2-chloro and 2-bromo substituents in the A -5a-H-3-ketone series.Yields of 90% are obtained within a reaction period of 5 hr at room temperature. A A -3-keto system in (1) is not attacked under these conditions. 

Irradiation of a 4,4-dimethyl-A -steroid with two moles of N-bromosuccini-mide gives the 7,7-dibromide (214), which can be dehydrobrominated to the novel 7-bromo-5,7-diene (215) or hydrolysed to the 5-en-7-one (216). Oxidation of 3/ -acetoxylanost-8-ene with chromic acid gave the known 8-en-7-one and 8-ene-7.11-dione. and also the 9(1 l)-en-7-one, apparently identical with Marker s a-keto-dihydrolanosteryl acetate . The acidic fraction from... 

We have studied the reaction of the potential afiSnity label, 3-bromo-acetoxyestrone, with human placental estradiol dehydrogenase and have found that it satisfies the first four criteria for an afiSnity label. Furthermore, the 17-keto group of this compound offers an opportunity to determine whether, after reaction with the enzyme, the covalently bound steroid is suitably positioned to serve as a substrate in the dehydrogenase reaction. We provide evidence that such is indeed the case. 

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