A Synthesis of the ABC Tricyclic Core of the Clionastatins Serves To Corroborate Their Proposed Structures

[Image: see text] A synthesis of the ABC tricyclic ring system of the clionastatins, an unusual pair of highly chlorinated androstane steroids, has been accomplished. This work provides strong support for the original structural proposal. An unexpected substrate-dependent reversal in alkene chlorination diastereoselectivity was critical to success. This approach should be amenable to an eventual enantioselective synthesis of the natural products themselves.