Site‐Selective and Metal‐Free Aliphatic CH Oxidation Enabled Synthesis of [5,24,25‐D3]‐(25S)‐Δ7‐Dafachronic acid

Steroid hormones play significant roles in both worms and mammalians. (25S)-Δ7-Dafachronic acid (Δ7-DA, 1) is a member of the dafachronic acid hormonal series that regulates both development and lifespan of C. elegans. Despite its importance, effective tools for the illumination of its mode of action are lacking. Herein, we report an efficient synthesis of trideuterated Δ7-DA, [5,24,25-D3]-(25S)-Δ7-dafachronic acid ([D3]-Δ7-DA, 2), as a useful chemical tool for subsequent biological studies. Key steps for this bioinspired synthesis approach include site-selective aliphatic CH oxidation mediated by methyl(trifluoromethyl)dioxirane (TFDO), and the iridium/phosphine-oxazoline-catalyzed late-stage asymmetric deuterium reduction.