Steroids are highly prevalent structures in small‐molecule therapeutics, with the level of oxidation being key to their biological activity and physicochemical properties. These C(sp3)‐rich tetracycles contain many stereocentres, which are important for creating specific vectors and protein binding orientations. Therefore, the ability to hydroxylate steroids with a high degree of regio‐, chemo‐ and stereoselectivity is essential for researchers working in this field. This review will cover three main methods for the hydroxylation of steroidal C(sp3)−H bonds: biocatalysis, metal‐catalysed C−H hydroxylation and organic oxidants, such as dioxiranes and oxaziridines.

Kinetic resolution using biocatalysis has proven to be an excellent complementary technique to traditional asymmetric catalysis for the production of enantioenriched compounds. Resolution using oxidative enzymes produces valuable oxygenated structures for use in synthetic route development. This Minireview focuses on enzymes which catalyse the insertion of an oxygen atom into the substrate and, in so doing, can achieve oxidative kinetic resolution. The Baeyer-Villiger rearrangement, epoxidation, and hydroxylation are included, and biological advancements in enzyme development, and applications of these key enantioenriched intermediates in natural product synthesis are discussed. Scheme 1-Representative early examples of enzymatic OKR. Lucy Harwood received her MSci degree in Chemistry from Queen's University, Belfast completing her final year research project on the use of sigmatropic rearrangements in synthesis in the group of Prof. P. Stevenson. She is currently conducting her doctoral studies at the University of Oxford in the groups of Prof. J. Robertson and Prof. L.-L. Wong developing mutant cytochrome P450s as general oxidation catalysts.

Kinetic resolution using biocatalysis has proven to be an excellent complementary technique to traditional asymmetric catalysis for the production of enantioenriched compounds. Resolution using oxidative enzymes produces valuable oxygenated structures for use in synthetic route development. This Minireview focuses on enzymes which catalyse the insertion of an oxygen atom into the substrate and, in so doing, can achieve oxidative kinetic resolution. The Baeyer–Villiger rearrangement, epoxidation, and hydroxylation are included, and biological advancements in enzyme development, and applications of these key enantioenriched intermediates in natural product synthesis are discussed.