There are disclosed a process for producing an α-acyloxy-α,β-unsaturated carbonyl compound represented by the general formula (VI):wherein Ri, R2 and R4 are independently hydrogen atoms or substituted or unsubstituted hydrocarbon residues, or Ri, R2 and R4, when taken together with one another in an optional combination, form a ring, R3 is a substituted or unsubstituted hydrocarbon residue, and indicates that the configuration may be either E-configuration or Z-configuration, in particular, a 20-acyloxy-17(20)-methylen-21-al-steroid represented by the partial structural formula (II):wherein R is a hydrocarbon residue, and indicates that the configuration of the acyloxy group and the formyl group bonded to the carbon atom at the 20-position may be either E-configuration or Z-configuration, which comprises oxidizing a propargyl ester represented by the general formula (V):wherein Ri, R2, R3 and R4 have the same meanings as defined above; an al-steroid compound having the above partial structural formula which is an intermediate for producing a 21-acyloxy-20-keto-delta16-steroid being extremely useful as an intermediate for important corticoids as drugs and obtained by being subjected said al-steroid to isomerization reaction; and a process for producing a 21-acyloxy-20-keto- delta16-steroid which comprises oxidation reaction and isomerization reaction.
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