Filamentous Fungi Potentially Useful Catalysts for the Biohydroxylations of Non-Activated Carbon Centers

Filamentous fungi are capable of catalyzing regio- and stereoselective hydroxylation on an extensive array of natural and synthetic hydrophobic organic substrates. A significant benefit of fungal hydroxylation is that non-activated carbon centers can be functionalized in ways that may not be easily emulated by classical organic means. The enzymes thought to perform the hydroxylations are cytochrome P450 monooxygenases. This review presents the evidence for the role of cytochrome P450s and summarizes the broad spectrum of substrates hydroxylated by various filamentous fungi in the twenty years prior to August 2000. Whole cell systems are generally preferred because monooxygenases that catalyze these reactions have not been isolated and characterized. Optimization of the hydroxylation conditions and the ability to accurately predict the biotransformation product(s) are necessary future developments before widespread synthetic practicality is achieved. Several recent developments in optimization techniques are also discussed including the use of protecting groups, varied experimental conditions, and the use of additives to the whole cell systems.