Biologically active compounds, nuclei location

The modification and enhancement of biological activity of drugs and hormones by fluorination represent one of the most fruitful recent developments in medicinal chemistry. Its first successes and most interesting subsequent developments were in the steroid field. Almost every new technique of introducing fluorine into organic compounds has been applied in this area and, as a result of both the gross and subtle chemical differences which steroids display at different locations of the nucleus, has produced a wealth of new chemistry. 

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