Two epimeric rearranged ergostanes, strophasterols A and B, with an unprecedented carbon skeleton were synthesized from ergosterol, both in 17 steps via a common secosteroidal intermediate. The conversion of ergosterol into the pivotal intermediate involved an efficient acid-catalyzed double-bond migration from ring B to ring D, oxidative cleavage of the double bond, and a completely diastereoselective acyl radical cyclization to form an isolated cyclopentanone ring unique to this recently discovered family of steroidal compounds produced by mushrooms. The intermediate was transformed stereodivergently into two epimeric cyclopentane derivatives through hydrogenation using two types of catalysts. One epimer was elaborated into strophasterol B by utilizing peracid oxidation of an iodide to provide an epoxide directly, and the other epimer was elaborated into strophasterol A, which is known to be a suppressor of endoplasmic reticulum stress.

Two protected 14,15-secoergostane derivatives suitable as pivotal intermediates for the synthesis of strophasterols A and B, anti-MRSA and neuronal cell-protecting natural products bearing a recently discovered strophastane skeleton, have been synthesized by two different routes. The first approach employed an oxidative cleavage of an α-hydroxy ketone intermediate with the Jones reagent as the key step to reach the targeted secoergostane from ergosterol in ten steps. In the second approach, an unprecedented reaction cascade composed of four reactions enabled us to obtain the secoergostane more efficiently in six steps.

Tw oe pimeric rearranged ergostanes,s trophasterols Aa nd B, with an unprecedented carbon skeleton were synthesized from ergosterol, both in 17 steps via ac ommon secosteroidal intermediate.T he conversion of ergosterol into the pivotal intermediate involved an efficient acid-catalyzed double-bond migration from ring Bt or ing D, oxidative cleavage of the double bond, and acompletely diastereoselective acyl radical cyclization to form an isolated cyclopentanone ring unique to this recently discovered family of steroidal compounds produced by mushrooms.T he intermediate was transformed stereodivergently into two epimeric cyclopentane derivatives through hydrogenation using two types of catalysts. One epimer was elaborated into strophasterol Bb yu tilizing peracid oxidation of an iodide to providea ne poxide directly, and the other epimer was elaborated into strophasterol A, which is knownt ob eas uppressor of endoplasmic reticulum stress.