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Patent / 1972

Betamethasone

Authors:
  • Ivan Villax
Source:
US 3792046
The title compd. (I, R = H) was prepd. Thus, bromination of 16.beta.-methyl-17.alpha.-hydroxypregna-1,4,9(11)-triene-3,20-dione with AcNHBr in THF-HClO4-H2O at 25-30.degree. gave 96% II (R = Br, Br1 = R2 = H), which was epoxidized with aq. NaOH in MeOH-CHCl3 under N at 0-3.degree. to give 92.6% 16.beta.-methyl-9,11-epoxy-17.alpha.-hydroxypregna-1,4-diene-3,20-dione (III). Fluorination of III with HF in DMF at 16-18.degree. gave 82.4% II (R = F, R1 = R2 = H), which was iodinated with iodine in the presence of CaCl2-CaO in MeOH at -10.degree. to -12.degree. under N in the dark to give 100% II (R = F, R1 = R2 = iodine) (IV). Refluxing IV with KOAc-HOAc for 1.5 hr in aq. Me2CO gave 86.6% I (R = Ac), which was hydrolyzed with 2N methanolic NaOMe to give 96.4% I (R = H).