Claisen condensation of 3-beta-acetyloxypregna-5,16-dien-20-one (I) with ethyl formate in the presence of NaOMe in pyridine, with simultaneous deacetylation, provided the corresponding 21-formyl derivative (II). Subsequent treatment of (II) with hydroxylamine yielded isoxazole (III) as the only regioisomer. Finally, Oppenauer oxidation of (III) with cyclohexanone and aluminum isopropoxide gave rise to the target alpha,beta-unsaturated ketone.