An Efficient Chemoenzymatic Synthesis of Chenodeoxycholic Acid from its Allo‐Epimer through Stereoselective Hydrogenation of 3‐Oxo‐chol‐Δ1,4‐dien‐24‐oate Scaffold

Abstract Commercially valuable chenodeoxycholic acid (CDCA) was firstly developed from undesirable allo ‐CDCA via multiple reactions: esterification, selective oxidation of C3‐hydroxy, the introduction of 1,4‐dien through IBX and TFA, the stereoselective hydrogenation by Pd/C under basic solution, deprotection, enzymatic reduction of C3‐carbonyl. During the process, highly selective oxidants were found to oxidize the C3‐hydroxy generating allo ‐3‐keto bile acid which was used as substrates to investigate the dehydrogenation under IBX, and the possible hydrogenation mechanism under Pd/C had been proposed based on the crystal data.