The acid-catalysed and photochemical rearrangements of some steroids

Hydrogenation of 6β-fluoro-3β,5-oxaethano-19-nor-5β-androst-9(10)-en-17-one (I[6a]) gives 6β-fluoro-3β,5-oxaethano-19-nor-5β,10α-androstan-17-one (II[1a]) and 6β-fluoro-3β,5-oxaethano-19-nor-5β,9β-androstan-17-one (II[2a]). Similarly, hydrogenation of 6β-fluoro-3β,5-oxaethano-19-nor-5β-pregn-9(10)-en-20-one (I[6b]) gives the corresponding 9α,10α-(II[1b]) and 9β,10β-(II[2b]) isomers. Treatment of the ether (II[2a]) with boron trifluoride–ether in acetic anhydride produces a mixture of 5-acetoxymethyl-6β-fluoro-19-nor-5β,9β-androst-2-en-17-one (II[3]), 3β-acetoxy-5-acetoxymethyl-6β-fluoro-19-nor-5β,9β-androstan-17-one (II[4]) and the 3α-epimer (II[5]). Chromium trioxide–acetic acid oxidation of the ether (II[1a]) affords 6β-fluoro-3α,5-methano-4-oxa-A-homo-19-nor-5α,10α-androst-4a,17-dione (II[6]). [Continues.]