Microbial hydroxylation of steroids. 10. Rearrangement during epoxidation and hydroxylation, and the stepwise nature of these enzymic reactions

Abstract

A series of unsaturated steroids has been incubated with fungi which are known to hydroxylate at a site corresponding to the allylic position in the analogous saturated steroids. In some cases, the anticipated hydroxylation occurred without rearrangement of the double bond. In a number of Instances, however, products were obtained whose structures implied that allylic rearrangement had occurred during the reaction. The formation of these products is consistent with a stepwise mechanism of enzymatic oxidation. Possible routes for product formation are presented which incorporate this proposal.HERBERT L. HOLLAND et ELLY RIEMLAND. Can. J. Chem. 63, 1121Chem. 63, (1985. On a fait incuber une sCrie de stero'ides non satures avec des champignons connus pour hydroxyler ii une site correspondant ti la position allylique des stCroi'des saturCs analogues. Dans quelques cas, I'hydroxylation prCvue se produit sans transposition de la double liaison. Toutefois, dans un bon nombre de cas, on a obtenu des produits dont les structures impliquent que des transpositions allyliques se sont produites au cours de la reaction. La formation de ces produits est en accord avec un mCcanisme de I'oxydation enzymatique qui impliquerait plusieurs Ctapes. On propose des voies rCactionnelles possibles qui incorporent cette proposition.[Traduit par le journal] IntroductionThe enzymatic conversion of a saturated carbon-hydrogen bond to hydroxyl, and the related enzymatic epoxidation of olefins, are most often catalyzed by cytochrome P-450 dependent mono-oxygenase enzymes (1). The mechanism of these oxidations is still in doubt, currently favoured possibilities being presented in Scheme I (for hydroxylation) and Scheme 2 (for epoxidation) (2).Evidence has recently been accumulating which supports a stepwise route for both of these reactions (routes B, Schemes 1 and 2) (3-8). This has taken the form of epimerization during hydroxylation (4), the trapping of carbon radical intermediates (5, 6), the observation of inversion of olefin geometry during epoxidation (3), and the detection of rearrangements during olefin oxidation (7,8).The hydroxylation of steroids by fungi has been shown in many cases to be a cytochrome P-450 dependent monooxygenase reaction (9-12). In order to further study the mechanism of the enzymatic oxidation of steroid substrates, we have now investigated the metabolism of a series of unsaturated steroids by fungi which are known to hydroxylate analogous saturated steroids at a position corresponding to an allylic carbon (13). The putative existence of a radical intermediate such as those shown in routes B of Schemes 1 and 2 now allows for the possibility of allylic rearrangements in these cases, and it was this aspect of the problem which we set out to study.

Side chain hydroxylation of aromatic hydrocarbons by fungi. Part 2. Isotope effects and mechanism

“…The key features are rapid, low-temperature conversion of (7) or (8) into the corresponding chloride by POCl,, and their stereospecific reaction with Super Deuteride or Super Hydride. 'l In our hands, the intermediate chlorides (10) and (11) were not optically stable at room temperature for prolonged periods. Their generation at lower temperature and immediate use is therefore indicated in the preparation of labelled ethylbenzenes of high optical purity.…”

Anabolic steroids detected in bodybuilding dietary supplements – a significant risk to public health

“…Although these data cannot confirm the exact conformation of the steroid detected, this same compound was detected in all these products according to the LC-MS data. [27][28][29] (See supplementary data for the NMR spectra, Figures S31-S34 and S37-S39. )…”

Preparatively useful transformations of steroids and morphine alkaloids byMucor piriformis

“…Fungi belonging to the genus Mucor have been reported to mainly effect hydroxylation at 14~t, ll0t, 7ct and 6fl-positions of various steroids (Tamm et al 1963;Vezina and Singh 1975;Holland and Riemland 1985;Madyastha and Srivatsan 1987;Krishnan et al 1991). However, much information has been covered by patents (Murray and Peterson 1957;Dodson and Tweitt 1960;Charney and Herzog 1967).…”