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Patent / 1982

Selective solvolysis

Plurichemie Anstalt

Source:
US 4343739
Corticosteroid esters I (R = H, F; R1 = H, trihaloacetyl; R2 = acyl; R3 = H, acyl; R2R3 = cyclic ortho ester group) underwent regioselective solvolysis-deacylation reactions. Thus, treatment of betamethasone 21-acetate 11-trifluoroacetate 17-valerate (20.0 g) with MeSO3H in abs. MeOH at 18.degree. for 24.5 h and then at 25.degree. for 2.75 h followed by hydrolysis with cold H2O gave 17.98 g betamethasone 11-trifluoroacetate 17-valerate. HCl and 4-MeC6H4SO3H were also effective catalysts for this deacetylation. Treatment of betamethasone 17,21-diacetete 11-trifluoroacetate (2.0 g) with NaOMe in water-free NaOH at 10.degree. for 5 min and then neutralization with 50% aq. HOac and hydrolysis with cold H2O gave 1.58 g betamethasone 17,21-diacetate.