Total Syntheses from BC and BD Fragments

In contrast to the syntheses considered in the preceding chapter, methods of constructing the steroid skeleton from bicyclic BC and BD derivatives have been used mainly for the production of nonaromatic steroids. This is connected with the nature of the reactions used for constructing ring A (Robinson s method and its numerous modifications). 

In correspondence with the three methods of building up the steroid skeleton considered in this chapter, the exposition of the material is divided into three sections. The first of them comprises total syntheses from BC fragments with the initial formation of ring A and the second syntheses with the initial formation of ring D. The third section comprises syntheses of steroid compounds from BD fragments. 

This type of total syntheses of steroid compounds relates mainly to the nonaromatic 19-methylsteroids. A consideration of literature data on these 

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