Steroids microbiological oxidation

Microbiological oxidation has proven of enormous value in steroid chemistry, often affording selective means of functionalizing remote and chemically inactivated positions. It will bear mentioning that the 11-oxygen for all commercially available corticoids is in fact introduced by such a reaction carried out on plant scale. Preparation of the 1-dehydro analogue of 207 involves biooxidation to introduce the 16-hydroxyl. Incubation of 6a-fluoroprednisolone... 

Side reactions of microbiological oxidation using the very same microorganisms can cause hydroxylation of steroids in different positions, using easily accessible progesterone [1-5] as an initial substance [1-5]. 

The discovery of this stereoselective hydroxylation at C-11 and the introduction of diosgenin as a cheap raw material had dramatic effects in reducing the cost of steroid hormones. Thus in the early 1950 s, the price of progesterone dropped within just three years from 80 to 3/g. In its turn cortisone cost about 200/g in 1949 whereas today its cost is less than l/g. Several other steroids are also prepared by processes which include a microbiological oxidation step among them, cortexone and fluocortolone. 

The application of a similar scheme for the isolation and identification of hydrocortisone was reported recently from this laboratory (7,8). In this case this steroid was present in a complex mixture of products resulting from the microbiological oxidation of ll-desoxy-17-hydroxycorticosterone... 

The beauty of the microbiological method lies in its ability to oxidize the structurally similar C-17 side chains of other steroids which contaminate sitosterol (e.g., campesterol, dihydrobrassicasterol, and stigmasterol—all of which carry the 3 3-hydroxy-5-ene structure) at both C-17 and 9a sites to compound XXXVIII. 

Microbiological conversions, microbiological iranrformaiions conversions of materials occurring in one or more stages, and catalysed by microorganisms. M.c. are the result of microbiological enzyme action, and often have no importance for the microbial cell. Several M.c. are important in the pharmaceutical industry. Examples are the stereospecific conversions of steroids, oxidation of sorbitol to sorbose by Acetobacter suboxydans (in the production of vitamin C), and the addition of acetaldehyde to benzalde-hyde by Saccharomyces cerevisiae. The product of this last reaction is phenylacetylcarbinol, a precursor for D-ephedrine synthesis. 

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