A solution of methacrylic acid (3.6 g, 41.8 mmol) in dimethylformamide (30 ml) is added dropwise to an ice cooled slurry of sodium hydride (60% suspension in paraffin oil) (1.5 g, 37.5 mmol) in dimethylformamide (50 ml). Once addition is complete, the mixture is allowed to warm to room temperature and is stirred for 1 h, the intermediate 4′-pentyl-bicyclohexyl-4-carboxylic acid 6-bromo-hexyl ester (15.0 g, 33.8 mmol) in dimethylformamide (100 ml) is added dropwise. The mixture is stirred at 50° C. over night. The mixture is cooled to room temperature, poured into icy water, and this is extracted three times with DCM. The DCM solution is washed with brine, water and then dried over sodium sulphate. The solution is evaporated to dryness and recrystallised from acetonitrile to afford a white waxy solid. Further purification is achieved by preparative HPLC using water/acetonitrile as eluant.
