Synthesis of an intriguing steroidal constitutional isomer

We recently described the synthesis of an unusual tricyclic system, whereby a cis-decalin was fused to a cis-hydrindane. Herein, we wish to describe the elaboration of this system towards steroid-like frameworks. This report describes how, en route to an attempted cardiotonic steroid synthesis, we stereoselectively functionalized the left most cyclohexyl ring with an ester ready for steroidal A-ring formation. Ultimately however, the required transposition of the cyclohexylketone did not occur as expected and resulted in the subsequent Robinson annulation forming an unusual steroidal constitutional isomer - the saturated cyclopenta[c]phenanthrene. Remarkably, such unusual tetracyclic connectivity has been reported just once in 70 years. (C) 2020 Elsevier Ltd. All rights reserved.