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

## TL;DR

This paper explores steroid photochemistry to efficiently convert accessible steroids into rare ones, demonstrated by a four-step synthesis of a natural compound analog.

## Contribution

A tunable and efficient method for steroid ring system remodeling using Δ1-keto-steroid photochemistry is developed.

## Key findings

- Photochemistry of Δ1-keto-steroids is simpler and more efficient than other steroid types.
- The method allows interconversion of accessible steroids into rare natural analogs.
- 5,6-dihydro-ophiopogonol A was synthesized in four steps from diosgenin.

## 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 Δ1‐3‐keto‐steroids. In terms of number of products obtained, the photochemistry of Δ1‐3‐keto‐steroids is less complicated than that of Δ4‐3‐keto‐ and Δ1,4‐3‐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).

Steroid photoreactivity was a major topic in the last century. This study revisits it by exploring the photochemistry of Δ1‐keto‐steroids, offering an efficient method to modify the classic steroid 6/6/6/5 ring system. This approach enables the transformation of accessible steroids into rare ones, demonstrated by synthesizing 5,6‐dihydro‐ophiopogonol A in four steps from diosgenin.