THE MICROBIOLOGICAL HYDROXYLATION OF SOME STEROIDS WITH A CORTICAL SIDE CHAIN BY CEPHALOSPORIUM APHIDICOLA JAMES R. HANSON* and A. CHRISTY HUNTER School of Chemistry, Physics and Environmental Science, University of Sussex, Brighton, Sussex, BN1 9QJ, U.K. (Received in revised form 23 March 1998) Key Word IndexÐCephalosporium aphidicola; hyphomycetes; microbiological hydroxylation; steroid; 21-hydroxypregna-4-en-3,20-dione. AbstractÐHydroxylation of pregna-4-en-3-ones at C-11a by the fungus Cephalosporium aphidicola is shown to be aected by the nature of the pregnane side chain whilst hydroxylation at C-6b is unaected. # 1998 Elsevier Science Ltd. All rights reserved INTRODUCTION In our studies on the microbiological hydroxylation of steroids by the fungus Cephalosporium aphidicola, we have noted a number of dierences between the hydroxylation of progesterone and testos- terone [1, 2]. Whereas progesterone (1) was e- ciently hydroxylated ®rst at C-11a and then at C-6b, testosterone (2) was hydroxylated at C-6b and the hydroxylation at C-11a was only a minor transformation. On the other hand testosterone was hydroxylated at C-14a, a transformation which was not observed with progesterone. Hydroxylation of progesterone at C-17a led to further hydroxylation at C-12b. In the light of these dierences, it was of interest to see how the hydroxylation pattern was modi®ed by the oxidation of the pregnane side chain which is a characteristic of the cortical hor- mones. In mammals oxidation of C-11 is an import- ant transformation of the cortical steroids leading to cortisol and cortisone. A number of other stu- dies, exempli®ed by Refs [3]±[6], have been reported on the microbiological transformation of cortical steroids. The major transformations which have been reported involve hydroxylation at C-6 and C-11, reduction of the D 4 -double bond and cleavage of the side chain. RESULTS AND DISCUSSION In order to examine the eect of oxidation of the side chain,the microbiological hydroxylation of 21-hydroxyprogesterone (deoxycorticosterone) (3), 17a,21-dihydroxyprogesterone (cortexolone) (7) and 16a,17a-epoxyprogesterone (9) by C. aphidicola was compared to the results obtained earlier with progesterone [1]. The substrates were incubated with the fungus in shake culture for 7 days. The results are tabulated (see Table 1). The sites of hydroxylation were established from changes (b-deshielding and g-gauche shielding eects) in the 13 C NMR spectra (see Table 2) [7]. The stereochemistry of the hydroxylation followed from the characteristic shape and multiplicity of the CH(OH) resonances and the eect of the additional hydroxyl group on the position of the H-18, H-19 and H-21 resonances in the 1 H NMR spectra [8]. Hydroxylation of 21-hydroxyprogesterone (3) proceeded eciently at C-6b and was accompanied by some reduction of the C-20 ketone to the alco- hol. In the previous work [1] on progesterone (1) this microbial reduction was shown to give the 20(R) alcohol. In contrast to the transformation of progesterone, hydroxylation at C-11a was a second- ary transformation. However, when a 17a-hydroxyl group was introduced as in 17a,21-dihydroxypro- gesterone (7), hydroxylation proceeded ineciently and only at C-12b rather than at C-11a or C-6b. Interestingly in the previous study [1] with pro- Phytochemistry Vol. 49, No. 8, pp. 2359±2362, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0031-9422/98/$ - see front matter PII: S0031-9422(98)00327-6 *Author to whom correspondence should be addressed. 2359