General Questions of Total Synthesis

In modern organic chemistry, synthesis still remains one of the main directions of its development, and the chemistry of the steroids is no exception to this. The value of total synthesis in steroid chemistry is due to a number of basic factors. 

First of all, total synthesis gives a definitive confirmation of the structure of the natural steroids and is the crowning stage of the study of their structure. In view of the fact that the total synthesis of all classes of natural steroids known at the present time has already been performed, this function of it has apparently receded into the field of history. 

In the investigation of the total synthesis of steroids, not only have new chemical reactions been discovered and ones known earlier modified, but extremely delicate methods for the selective performance of chemical transformations have been developed. Moreover, with the results obtained in total steroid synthesis, the stereochemistry of condensed polycyclic systems has been given a new impetus and further development. 

Total synthesis is in the mainstream of modern tendencies of the development of steroid chemistry, the main characteristic of which is the synthesis of modified steroid compounds. The methods of total synthesis open up greater possibilities for the modification of molecules than synthesis from natural compounds with the skeleton already formed. It is obvious that the further we depart from natural steroids in the modification process, the better are the prospects for the use of total synthesis. Consequently, at the present time it is possible to outline the field of modification within which total synthesis is the most suitable method, if not the only possible one. This field includes, for example, 18-homo-steroids and the highly unsaturated -steroids. However, here 

One of them is the change in the stereochemistry of the steroid molecule, which enables the precise stereochemical conditions for the hormonal activity of the steroids to be studied. In this connection it is sufficient to 

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