Synthesis and in vitro biological evaluation of ring B abeo-sterols as novel inhibitors of Mycobacterium tuberculosis

A series of 3β-hydroxy steroid analogues possessing a contracted cyclopentane B-ring were prepared based on the initial activity screening of a recently reported naturally occurring marine 5(6 → 7)abeo-sterol against Mycobacterium tuberculosis. All of the novel ring B abeo-sterols synthesized showed good inhibitory activity, whereas none of the starting steroids based on the common 3β-hydroxy-Δ5-cholestane nucleus, proved to be active. Therefore, the 5(6 → 7)abeo-sterol nucleus present in compounds 3, 5, 7, 9, and 11 represents a novel scaffold for the development of new antitubercular agents.