Baeyer–Villiger oxidation of some steroids by Aspergillus tamarii MRC 72400

Abstract

Biotransformations of epiandrosterone (1), dehydroepiandrosterone (2), testosterone (3), progesterone (4) and pregnenolone (5) by Aspergillus tamarii MRC 72400 for 5 days have been reported and the results of these incubations have been compared with previously published data obtained with Aspergillus tamarii QM 1223. A. tamarii MRC 72400 showed higher Bayer-Villiger monooxygenase activities than A. tamarii QM 1223 did. Apart from pregnenolone (5), A. tamarii MRC 72400 metabolized these steroids in different ways. Incubation of epiandrosterone (1) afforded 3β,11β-dihydroxy-5α-androstan-17-one (6) (3%) and 3β-hydroxy-17a-oxa-D-homo-5α-androstan-17-one (7) (9.5%). Incubation of dehydroepiandrosterone (2) afforded 3β-hydroxy-17a-oxa-D-homoandrost-5-en-17-one (8) (28%), testolactone (9) (6%), 3β,7β-dihydroxyandrost-5-en-17-one (10) (13%) and 3β,7α-dihydroxyandrost-5-en-17-one (11) (24%). Incubation of testosterone (3) afforded testolactone (9) (58%). Incubation of progesterone (4) also afforded testolactone (9), however in higher yield (86%). Incubation of pregnenolone (5) afforded 3β-hydroxy-17a-oxa-D-homoandrost-5-en-17-one (8) (25%) and testolactone (9) (27%).A number of investigations involving microbial biotransformations of a wide range of steroidal substrates have been carried out due to their potential for the preparation of more valuable and functionalized compounds such as steroid drugs and hormones 1-3 . There are still enormous efforts to increase the efficiency of microbial steroid biotransformations and to find new useful microorganisms and reactions 1 . For example, some of these steroid biotransformations have been carried out using Aspergillus wentii 4 , Penicillium digitatum 5 and Aspergillus terreus 6 . A. wentii showed some high hydroxylase activities whereas P. digitatum and A. terreus showed some low 5α-reductase and Baeyer-Villiger monooxygenase (BVMO) activities, respectively.

Baeyer-Villiger Oxidation of Some C19 Steroids by Penicillium lanosocoeruleum

“…The use of the chimeric enzyme PASTMO (a hybrid of phenylacetone monooxygenase (PAMO) and bacterial steroid monooxygenase (STMO) from Rhodococcus rhodochrous ) in the biotransformation of progesterone afforded the final lactone (testololactone) with a moderate (19%) conversion [4]. Among microorganisms, fungal species of the Penicillium [5,6,7,8,9,10], Aspergillus [11,12,13,14,15,16,17,18,19,20] and Fusarium genera [21,22,23] are especially known to transform 4-en-3-oxo and 3β-hydroxy-5-ene C 21 as well as C 19 steroids. Enzymes performing oxidation belong to the family of NADPH-dependent steroid Baeyer-Villiger monooxygenases (BVMOs) containing FAD as a cofactor.…”

“…P. camemberti was able to carry out the oxidation of pregnenolone and DHEA to testololactone, which could be formed via two routes: through 4-en-3-ketone or 3β-hydroxylactone [9]. In most cases of transformations described in literature, the steroids, besides the Baeyer-Villiger oxidation, also underwent hydroxylation, reduction or dehydrogenation [8,12,15,16,19,23,29]. The mixtures of metabolites formed during the transformations led to difficulties in product purification.…”

Biotransformation of Androst-4-Ene-3,17-Dione by Some Fungi

“…In the 13 C NMR spectrum of 2, the resonance attributed to the 17-ketone (δ C 220.43 ppm) of 1 was replaced by that for a CH(OH) (δ C 81.44 ppm). The metabolite 3 showed a new carbon atom resonance at δ C 80.67 ppm in its 13 C NMR spectrum whilst it did not show any new resonance in the range 3-5 ppm in its 1 H NMR spectrum, indicating the presence of a tertiary hydroxyl group. The downfield shifts for C-8 (Δδ C 2.78 ppm) and C-15 (Δδ C 8.51 ppm) and γ-gauche upfield shifts for C-7 (Δδ C 5.70 ppm) and C-16 (Δδ C 2.67 ppm) compared to 1 were in accordance with the presence of a 14α-hydroxyl group.…”

“…The structures of the metabolites (Fig. 1), which were known were established by comparing their 1 H NMR and 13 C NMR spectra (Table 1) with those of the starting material and the literature values. [5][6][7][8][9][10][11] All of the compounds retained the resonances assigned to the 4-ene-3-keto moiety of 1.…”

“…These changes were further in accordance with the presence of a 15β hydroxyl group. The 13 Incubation of androst-4-ene-3,17-dione 1 with A. tamarii MRC 72400 for 5 days afforded three metabolites (Table 2) identified as 17β-hydroxyandrost-4-en-3-one 2, 11β-hydroxyandrost-4-ene-3,17-dione 8 and 17a-oxa-D-homo-androst-4-ene-3,17dione 9. The structure of 2 was identified by comparison of its NMR spectra with those of a previously isolated metabolite.…”