Hydrocortisone, transformation

A third advancement in microbial biotechnology of steroid production was the abiUty to introduce a 16a-hydroxyl group microbiologicaHy (163). Modifications of the liP-hydroxylation, 16a-hydroxylation 1,2-dehydrogenation microbial processes are used for the synthesis of hydrocortisone, prednisolone, triamcinolone, and other steroid pharmaceuticals. A few microbial transformations that have been used to manufacture steroids are Hsted in Table 1 (164). 

One of the first indications that the antiinflammatory potency of the corticoids could be increased was the observation that incorporation of a 9a-fluoro group in hydrocortisone resulted in a tenfold increase in activity. Treatment of hydrocortisone acetate (170a) with phosphorus oxychloride in pyridine yields the corresponding olefin, 172. This, on being subjected to the reaction sequence depicted in the transformation of 104 to 108 (addition of HOBr, closure to the epoxide and ring opening with HF),... 

The science of biotransformations has been investigated since the days of Pasteur[1l However, progress in the use of enzymes and whole cells in synthetic organic chemistry was relatively slow until the 1950s, when the use of microorganisms to modify the steroid nucleus was studied in industry and academic laboratories. Thus conversions such as the transformation of 17a-acetoxy-l 1-deoxycortisol into cortisol (hydrocortisone) (1), using the microorganism... 

An important transformation in steroid biochemistry is the conversion of pregnenolone into progesterone. Progesterone is a female sex hormone, a progestogen, but this reaction is also involved in the production of corticosteroids such as hydrocortisone and aldosterone. The reaction also occurs in plants, and features in the formation of cardioactive glycosides, such as digitoxin in foxglove. 

A strain of Rhizopus nigricans performs a key transformation in the synthesis of hydrocortisone (13.51) (Scheme 13.9).19 The mold introduces a hydroxyl group... 

The first recorded 11/ -hydroxylation of a steroid was the transformation of 1 l-deoxy-17-hy-droxycorticosterone (1) into hydrocortisone (2) with Streptomyces fradiae205, albeit in very low yield. The first practical 11/J-hydroxylation processes were those using Curvularia lunala2 206 and Cunninghamella blakesleeana207-20R. The special strain, Curvularia lunata NRRL 2380, discovered via extensive screening operations, has continued to be important for the commercial production of hydrocortisone from 1. 

In the case of steroidal propargylic alcohols the first rearrangement produced a mixture of allenyl sulfoxides, epimeric at the sulfur atom, which reacted with an added nucleophile to produce substituted allylic sulfoxides. Rearrangement of the sulfoxide resulted in the exclusive formation of a-hydroxy derivatives. This reaction sequence has been applied in a synthesis of hydrocortisone acetate74 (Nu = OCH3) from androstene-3,17-dione and in a transformation of mesantrol75 (Nu = malonate) to a spirolactone. 

The mere introduction of a double bond transforms hydrocortisone to prednisolone, a big biological change see Table 34.1 for relative potencies 1.0 1.0 to 4 0.8. 

The polymers generally employed in forming aqueous two-phase systems are quite hydrophilic as compared with organic solvents there is, however, a marked difference in hydrophobicity of the phase polymers. Thus, by extraction into the more hydrophobic phase it may be possible to design bioconversion in aqueous two-phase systems of substances of low water solubility. To this aim, we examined the transformation of hydrocortisone to prednisolone by Arthrobacter simplex cells in 25% PEG 8000 - 6% Dextran T40 system (18). Our studies showed that while the cells preferred the bottom phase, the Kpart of the steroid was in favour of the PEG rich upper phase (Kpart 3.0 andW.O for hydrocortisone and prednisolone respectively). The reaction rate was found to be comparable with those of systems in which the organic solvent had been included, which could be due to the efficient mass transfer between the two phases. Due to the high top to bottom phase volume ratio (8.5 1) a recovery of 98-99% could be obtained in the top phase. 

After the complete transformation, the PEG rich phase could be passed over a column of hydrophobic sorbent for the extraction of prednisolone, and then recirculated to the reactor with additional substrate. The bacterial cells could be used repeatedly for the batch conversions of hydrocortisone, and also had the possibility of being reactivated by supply of nutrients. 

One of the early experiments, which was run by Nobile in our laboratories, was the treatment of the diacetate with Corynebacterium simplex. The rationale was that an apparently related and then unavailable culture, Corynebacterium mediolanum, had been shown by Mamoli to have a good esterase (M-541, M-546). As it turned out, C. simplex afforded an interesting new reaction product in high yield, but that product was not hydrocortisone. More detailed investigation with other substrates, particularly Compound S, showed that the major transformation was 1-dehydrogenation... 

Since we had shown that C. simplex dehydrogenated without concomitant side-chain degradation, we were able to use this transformation to prepare the previously unknown 1-dehydro analogs of cortisone and hydrocortisone, later named prednisone and prednisolone, respectively. These were tested in animals by Tolksdorf, Perlman,... 

The pretreatment of rats with desipramine resulted in delayed stomach emptying and, hence, slowed absorption of phenylbutazone, oxyphenbutazone, hydrocortisone, and salicylate.On the other hand, desipramine had no apparent effect on the absorption of orally administered amphetamine or phenobarbital. In another study, the interactions of a variety of acutely and chronically administered contraceptive agents and their effect on pentobarbital narcosis in the rat, as well as on certain metabolic transformations in vitro, were examined. Medroxyprogesterone, alone or in combination with ethynylestradiol, stimulated the metabolism of 7nitroanisole, aminopyrine, and aniline in vitro, although these effects cure not as marked as those seen with well-known Inducers such as phenobarbital and pesticides. 

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