Steroids microbial oxidation

Experimental procedures have been described in which the desired reactions have been carried out either by whole microbial cells or by enzymes (1—3). These involve carbohydrates (qv) (4,5) steroids (qv), sterols, and bile acids (6—11) nonsteroid cycHc compounds (12) ahcycHc and alkane hydroxylations (13—16) alkaloids (7,17,18) various pharmaceuticals (qv) (19—21), including antibiotics (19—24) and miscellaneous natural products (25—27). Reviews of the microbial oxidation of aUphatic and aromatic hydrocarbons (qv) (28), monoterpenes (29,30), pesticides (qv) (31,32), lignin (qv) (33,34), flavors and fragrances (35), and other organic molecules (8,12,36,37) have been pubflshed (see Enzyp applications, industrial Enzyt s in organic synthesis Elavors AND spices). 

I aradve microbial oxidations have long been practiced in organic synthesis, perhq>s most prominently in the steroidal field, and a number of comprehensive and specialized reviews have appeared. The most recent review, publi ed in 1981, covers most aspects of biochemical oxidations, and gives an ex-... 

There have been a number of previous reviews on microbial oxidations of teipenes. Monoter-penes are often degraded progressively after an initial hydroxylation step, but di-, tri- and sesqui-tetpenes can be converted more selectively, to accumulate useful quantities of hydroxyla products. Less systematic work on the microbial oxidation of terpenoids has l n carried out than in the case of steroids, and therefore prediction of the regio- and stereo-chemistry is scarcely possible. 

There are few examples of synthetically useful allylic hydroxylations except in the steroidal field (Section 1.4.4.2), although some others are shown in Sections 1.4.3.3 and 1.4.1. Previous reviews on microbial oxidation have also included some examples of allylic oxidations. 

A number of microbial reagents have been used for successful oxidation of steroids, isoprenoids, alkaloids, hydrocarbons and other type of molecules. A number of reviews and monographs are available. Here we have given few cases which offer synthetic utility because they can afford excellent yield or they give single product that is inaccessible by other methods. Following are some typical microbial oxidations ... 

Scheme 12.9 Two examples of microbial oxidations of steroids 1 ip-hydroxylation of 11-deoxycortisol (26) to hydrocortisone (27), and production of pravastatin (29) by oxidation...

Fig. 2. Oxidation and reduction reactions using microbial transformation for steroid synthesis.

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