Steroid biocatalytic synthesis

Ferrero, M. and Gotor, V. (2000) Biocatalytic synthesis of steroids, in Stereoselective Biocatalysis (ed. R.N. Patel), Marcel Dekker, New York, USA, Chapter... 

Since the beginning of the 20th century, organic solvents have been used in enzymatic reaction media [30]. Biocatalytic reactions in water-organic biphasic media were first carried out by Cremonesi et al. [31] and by Buckland et al. [32] less than 30 years ago. Their work aimed at the conversion of high concentrations of poorly water soluble components, particularly steroids. Later, biphasic systems were used for enzyme-catalyzed synthesis reactions that were unfavored in water, changing the reaction equilibrium towards the higher yield of the product, such as esters or peptides. 

Biocatalytic asymmetric oxidations were developed very early for key steps in the production of vitamin C [9] and steroid hormones [10] and for a series of applications in organic synthesis [8], as illustrated in Figure 20.2. The use of biocatalysts in oxidation reactions is growing [11-15] and the inherent chirality of the enzymes enables a wide variety of biocatalytic asymmetric oxidations, an overview of which is given in the next six sections. 

Since the beginning of enzyme catalysis in microemulsions in the late 1970s, several biocatalytic transformations of various hydrophilic and hydrophobic substrates have been demonstrated. Examples include reverse hydrolytic reactions such as peptide synthesis [44], synthesis of esters through esterification and transesterification reactions [42,45-48], resolution of racemic amino acids [49], oxidation and reduction of steroids and terpenes [50,51], electron-transfer reactions, [52], production of hydrogen [53], and synthesis of phenolic and aromatic amine polymers [54]. Isolated enzymes including various hydrolytic enzymes (proteases, lipases, esterases, glucosidases), oxidoreductases, as well as multienzyme systems [52], were anployed. 

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