Acetic anhydride (40 μL, 0.42 mmol) was added to a stirred solution of 5-biphenyl-4-yl-3-hydroxy-pentanoic acid tert-butyl ester (Intermediate 3, 54 mg, 0.17 mmol), 4-dimethylaminopyridine (5.0 mg, 41 μmol) and pyridine (54 μL, 0.66 mol) in dichloromethane (1 mL) at room temperature under nitrogen. Stirring was continued for 12 hours at room temperature before the addition of 2 M hydrochloric acid (5 mL) and dichloromethane (5 mL). The phases were separated and aqueous phase extracted with dichloromethane (3×5 mL). The organic phases were combined, washed with brine (5 mL) and dried (MgSO4). The solvent was removed by evaporation under reduced pressure to give the title compound (45 mg, 74%) as a colourless gum. LC/MS: 3.91 min; z/e 386, calcd (M+NH4) 386. 1H NMR (400 MHz: CDCl3): 7.59 (2 H), 7.52 (2 H), 7.42 (2 H), 7.33 (1 H), 7.25 (2 H), 5.29 (1 H), 2.70 (2 H), 2.53 (2 H), 2.05 (3 H), 1.97 (2H), 1.42 (9 H).
