Summary and procedures for 19-norsteroids

In the previous sections the various possibilities for the production of 19-norsteroids from 19-substituted compounds have been reviewed. It is virtually impossible to compare the efficiency of the various procedures since optimal conditions are usually not described. 

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. 

The conversion of 3y5,17l5-diacetoxy-6i5-hydroxy-19-oximinoandrostane to 19-norandrostene-3,17-dione is achieved in 40% yield. 

The conversion of 3y5-acetoxy-5a-bromo-6y5-hydroxyandrostan-17-one to 19-norandrost-4-ene-3,17-dione via nitrite photolysis, nitrosation and oxidation to the 6)5,19-lactone results in an overall yield of about 8%, but clearly optimal yields have not been achieved. 

Selected examples for specific reactions sequences which will illustrate possible combinations for the preparation of 19-norsteroids via 19-functional-ized intermediates are given below. 

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III. Preparation of 19-Norsteroids from 19-Substituted Steroids / 264 Transformations of 6(3, 19-ethers / 264 Transformation of 19-oximino derivatives / 268 Removal of the C-10 substituent / 272 Summary and procedures for 19-norsteroids / 278... 

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