Chemoenzymatic Total Synthesis of (+)-10-Keto-Oxycodone from Phenethyl Acetate

The total synthesis of (+)-10-keto-oxycodone was attained from phenethyl acetate in a stereoselective manner. Absolute stereochemistry was established via enzymatic dihydroxylation of phenethyl acetate with the recombinant strain JM109 (pDTG601A) that furnished the corresponding cis-cyclohexadienediol whose configuration corresponds to the absolute stereochemistry of the ring C of (+)-10-keto-oxycodone. Intramolecular Heck reaction was utilized to establish the quaternary carbon at C-13, along with the dibenzodihydrofuran functionality. The C-14 hydroxyl and C-10 ketone were installed via SmI₂-mediated radical cyclization, and oxidation of a benzylic alcohol (obtained from an intermediate nitrate azide), respectively. The synthesis of (+)-10-keto-oxycodone was completed in a total of 14 operations (21 steps) and an overall yield of ~2%. Experimental and spectral data are provided for key intermediates and new compounds.