Studies on the stability of corticosteroids VI. Kinetics of the rearrangement of betamethasone-17-valerate to the 21-valerate ester in aqueous solution
1981; Elsevier BV; Volume: 7; Issue: 3 Linguagem: Inglês
10.1016/0378-5173(81)90105-8
ISSN1873-3476
AutoresHenning Bundgaard, Jens Hansen,
Tópico(s)Estrogen and related hormone effects
ResumoThe kinetics of the degradation of betamethasone-17-valerate in aqueous solutions of pH 0.5–8 have been investigated at 60°C using a reversed-phase HPLC procedure for determining remaining steroid and the products of its degradation, betamethasone-21-valerate and betamethasone. The overall degradation was shown to proceed entirely through a rearrangement of the 17-valerate ester to the 21-valerate ester followed by hydrolysis of the latter to yield betamethasone. The acyl group migration from C17 to C21 was subject to both specific acid and base catalysis as well as to catalysis by water. The pH-rate profile for the rearrangement showed a minimum at pH 3.5.
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