Optimization of Steroid Photochemistry and Its Application in the Synthesis of 5,6‐Dihydro‐Ophiopogonol A

Abstract The photoreactivity of steroids represented a hot topic in the middle of the last century and in this project, we “rediscover” it through the exploration of the photochemical behavior of Δ 1 ‐3‐keto‐steroids. In terms of number of products obtained, the photochemistry of Δ 1 ‐3‐keto‐steroids is less complicated than that of Δ 4 ‐3‐keto‐ and Δ 1,4 ‐3‐keto‐steroids, furnishing an efficient and tunable method to remodel the classic steroid 6/6/6/5 ring system. In this scenario, this approach can represent a simple strategy to interconvert a class of easily available steroids to another difficult‐to‐access from natural sources. As a proof of concept, the synthesis 5,6‐dihydro‐ophiopogonol A ( 11 ), a very close analog of natural ophiopogonol A ( 7 ), was accomplished in just four steps starting from easily available diosgenin ( 8 ).