Studies on Betamethasone : Behavior of Betamethasone in Acid or Alkaline Medium, Photolysis, and Oxidation

Abstract
To investigate the stability of betamethasone (I) in the pharmaceutical preparation, degradation in acid or alkaline medium, photolysis and oxidation reaction of I were performed under various conditions. On degradation in acid medium, I gave a mixture of 2 isomers of 9.alpha.-fluoro-11.beta.,20-dihydroxy-16.beta.-methylpregna-1,4,17(20)-trien-21-al-3-one and 9.alpha.-fluoro-11.beta.,21-dihydroxy-16-methylpregna-1,4,16-triene-3,20-dione. In alkaline conditions, I afforded 2 products, 9.alpha.-fluoro-11.beta.,17.alpha.-dihydroxy-16.beta.-methylandrosta-1,4-dien-3-one-17-carboxylic acid and 9.alpha.-fluoro-11.beta.-hydroxy-16.beta.-methylandrosta-1,4-diene-3,17-dione (V). Compound V was also obtained by oxidation with KMnO4. The photolysis product, 9.alpha.-fluoro-11.beta.,17.alpha.,21-trihydroxy-16.beta.-methyl-1,5.beta.-cyclopregn-3-ene-2,20-dione, was obtained by photo rearrangement of the 1,4-diene-3-keto steroid in considerable yield.

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