A solution of 3-cyclohexyl-1-[4-[4-(2-hydroxyphenyl)-1-piperidinyl]butan-1-yl]-2-imidazolidinone (1 g, prepared from 4-(2-hydroxyphenyl)piperidine (described in Example 5) and 1a by the method described in Example 4) in dry methylene chloride (10 ml) was cooled to −20° C. Isobutylene (5 ml, condensed at −25° C.) was added under a nitrogen atmosphere followed by addition of trifluoromethanesulfonic acid (0.4 ml). The mixture was stirred for 3 h at −20° C. followed by addition of triethylamine (2 mL). After warming to room temperature the reaction mixture was concentrated in vacuo followed by addition of 2 M ammonia and extraction with methylene chloride. The organic phase was dried over magnesium sulfate and concentrated in vacuo leaving an oil which was purified by flash chromatography (silica gel, eluent: ethyl acetate/MeOH/triethylamine 97:2:1). The resulting colorless oil was dissolved in a mixture of ethyl acetate and acetone. Addition of oxalic acid gave the title compound, 10a, as a crystalline material. Yield: 0.8 g, mp: 147-53° C. 1H NMR (DMSO-d6): δ 0.95-2.10 (m, 18H), 1.35 (s, 9H), 2.85-3.15 (m, 7H), 3.25 (s, 4H), 3.35-3.60 (m, 3H), 6.90-7.25 (m, 4H).
