Rhizopus arrhizus, steroid hydroxylation

In every case the information provided has been obtained by collating public domain sources of information, but unfortunately very often little data is available, particularly on commercial aspects, even for products that have proved to be big successes. Thus microbial biotransformations for steroid modification, particularly stereoselective hydroxylations, such as the use of Rhizopus arrhizus to convert progesterone into antiinflammatory and other dmgs via 11- -hydroxyprogestrone, have proved to be very successful. However, comparatively little useful information exists from public domain sources, despite (or perhaps because) a market of hundreds of millions /a exists for such microbially transformed steroids (cortisone, aldosterone, prednisolone and prednisone etc.) produced by microbial hydroxylation and dehydrogenation reactions coupled with complimentary chemical steps. 

Several hydroxylation biotransformations have been conunercialised, such as steroid hydroxylation, e.g. the 11-bf-hydroxylation of progesterone by Rhizopus arrhizus, 6-... 

The first recorded microbial hydroxylation of a steroid was that at the 7-position of cholesterol using Proactinomyces sp.2. Although this may have been 7/J-hydroxylation, an unambigious assignment cannot be made. Subsequently, unequivocal 7/ -hydroxylation by Rhizopus strains was observed. The mold Rhizopus arrhizus, which induces 6/f- and 1 la-hydroxylations in 4-en-3-one-steroids (e.g., androst-4-ene-3,17-dione), hydroxylates 3/ -hydroxypregn-5-en-20-one in positions Iji and 11a, and compounds of the 5a-pregnane series in the 7/i-position (see Table 8)154,4. 

Secondary steroidal alcohols react in preference to primary allylic alcohols in biochemical oxidations usingJihizopus arrhizus and Helicostylum piriforme or Cunninghamella blakesleeana. However, the reaction is complicated by hydroxylations in positions 6 (with Rhizopus arrhizus) and 9 (with Helicostylum piriforme or Cunninghamella blakesleeana) [1059]. 

The microbiological hydroxylation of the steroid progesterone (1.35) at C-11 by Rhizopus arrhizus was reported in 1952. This biotransformation, which is now carried out commercially on a substantial scale, provided the facile means of... 

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