Abstract
The synthesis of 7-fluoro-B-homo-19-norcholest-5 (10)-en-3β-ol acetate (1) was examined by utilizing diethyl (2-chloro-1, 1, 2-trifluoroethyl) amine (FAR), diethylaminosulfur trifluoride (DAST), and/or hexafluoropropene-diethylamine (FPA) as fluorinating agents for cholest-5-en-3β, 19-diol 3-acetate (2), 6β-hydroxymethyl-19-norcholest-5 (10)-en-3β-ol 3-acetate (9), 7β-hydroxy-B-homo-19-norcholest-5 (10)-en-3β-ol 3-acetate (12), and 3β-acetoxy-6β-hydroxy-5β, 19-cyclocholestane (13). The treatment of 2 and 9 with these fluorinating agents gave the 7-fluoro-B-homo-5 (10)-ene (1) in poor yield together with the cyclopropane products, 3β-acetoxy-5β, 6β-methanocholest-1 (10)-ene (3) and 3β-acetoxy-5β, 6β-methanocholest-9-ene (4). When 12 was allowed to react with FAR at -78°C, the required 1 was produced in 43% yield. The most satisfactory result, however, was obtained by the reaction of 13 with FAR at -78°C, which afforded the 7-fluoro-B-homo-5 (10)-ene (1) in 64% yield.
