 As for example 2,3-dinor-6-keto Prostaglandin F1α is produced by beta oxidation of the parent compound 6-keto Prostaglandin F1α.Here, though actually carbon 1 & 2 are lost by oxidation.The new Carbon 1 has now become a CCOH similar to the parent compound, looking as if just carbon 2 & 3 have been removed from the parent compound.