New 9,10-secosteroids from biotransformations of hyodeoxycholic acid with Rhodococcus spp.

Abstract

The biotransformations of hyodeoxycholic acid with various Rhodococcus spp. are reported. Some strains (i.e., Rhodococcus zopfii, Rhodococcus ruber, and Rhodococcus aetherivorans) are able to partially degrade the side chain at C(17) to afford 6α-hydroxy-3-oxo-23,24-dinor-5β-cholan-22-oic acid (2; 23%) and 6α-hydroxy-3-oxo-23,24-dinorchol-1,4-dien-22-oic acid (3; 23-30%), together with two new 9,10-secosteroids 4 and 5 (10-45%), still bearing the partial side chain at C(17) and adopting an intramolecular hemiacetal form. In addition, the 9,10-secosteroid 5 showed an unprecedented C(4)-hydroxylation. The new secosteroids were fully characterized by MS, IR, NMR, and 2D-NMR analyses. Copyright © 2013 Verlag Helvetica Chimica Acta AG, Zürich.