ABSTRACT
The pharmaceutical properties and the high cost of manufacturing steroids made any approach that permits mild and efficient modifications of the compounds a noteworthy achievement. As a result of this effort, highly selective synthetic procedures for the transformation of complex derivatives have been developed. This kind of biologically active molecule, containing different sensitive functional groups, appeared to be more and more suitable as a vehicle for exploiting the potentialities of enzymes in organic synthesis, mainly consisting of mild reaction conditions and excellent regio- and/or stereoselectivity. This chapter discusses the applications of isolated enzymes, crude or purified. At first glimpse, it is evident that there are two main parameters involved in any enzymatic transformation: the origin and catalytic properties of the different enzymes and the milieus in which the reactions have been performed. When free enzymes are employed, very high rates of shaking must be avoided because enzymes can become destabilized.
