Corticosteroids ketonic groups

Betamethasone is well absorbed after oral administration to be extensively bound to plasma proteins in humans, dogs, cows, and rats. Its metabolism does not differ of the other corticosteroids, involving oxidation of the 11 -hydroxyl group to ketone, reduction of the ketone group at the position C-20 to give the corresponding alcohol, and hydroxylation at the C-6 position and loss of the C-17 side chain to give 17-oxosteroids. 

The C-17 side-chain of corticosteroids does not contain a chromophoric group suitable for spectrophotometric measurement, nor does oxidation of the chain lead directly to spectrophotometrically active derivatives. However, the 20-keto group of the 17 a-ketol side-chain, as a chirally perturbed chromophoric group, has an optically active absorbance band in the interval 270-300 nm that is characteristic of the n-7T electronic transition for saturated ketones. An intense positive Cotton effect is observed in the CD spectra see the CD spectra for hydrocortisone and cortisone in Figures 8 and 9. 

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