Chemoenzymatic synthesis of C14-functionalized steroids

Fuzhen Song, Mengmeng Zheng, Junlin Wang, Huanhuan Liu, Zhi Lin, Benben Liu, Zixin Deng, Hengjiang Cong, Qianghui Zhou & Xudong Qu

Nature Synthesis (2023)

https://www.nature.com/articles/s44160-023-00280-z

Abstract

C14-functionalized steroids display biological activity and have been used as medicines. The lack of synthetic methods to access C14-functionalized steroids has, however, impeded steroidal drug discovery. In the present article, we report a modular chemoenzymatic synthesis of a diverse range of C14-functionalized steroids. This method was enabled through identification of a C14α-hydroxylase (CYP14A) from Cochliobolus lunatus, which displays high catalytic efficiency and substrate promiscuity. Protein engineering of CYP14A generated two variants, I111L–M115K and I111L–V124W, with greatly improved C14-hydroxy regiocontrol. Using this biocatalytic method, a range of C14α-hydroxy steroids with a C17 side chain were prepared in good yields, and were transformed into ∆14 olefins through a superficial elimination. The ∆14 olefin served as a versatile handle to install a variety of functional groups at the C14 position through hydro- or difunctionalization. The utility of this method was further demonstrated through application to concise semisynthesis of cardenolide periplogenin, (+)-digitoxigenin and its three diastereomers.