To a stirred solution of [7-(5-{3-chloro-4-[(1-methylethyl)oxy]phenyl}-1,2,4-oxadiazol-3-yl)-1-methyl-1H-indol-3-yl]acetaldehyde (D88) (50 mg), L-proline (28 mg) and acetic acid (0.1 mL) in DCM (10 mL) stirred at 20° C. was added sodium triacetoxyborohydride (52 mg). The reaction was stirred at 20° C. for 3 h. The mixture was concentrated and the residue was partitioned between ethyl acetate (25 mL) and aqueous HCl (2 M, 25 mL). The organic phase was washed with water (25 mL) and brine (25 mL), dried over anhydrous sodium sulphate and evaporated to give the crude product, which was purified by Mass Directed Auto Prep to afford 1-{2-[7-(5-{3-chloro-4-[(1-methylethyl)oxy]phenyl}-1,2,4-oxadiazol-3-yl)-1-methyl-1H-indol-3-yl]ethyl}-L-proline (E69) (12 mg, TFA salt). δH (DMSO-d6, 400 MHz): 1.35 (6H, d), 1.71 (1H, m), 1.94 (2H, m), 2.16 (1H, m), 2.95 (1H, m), 3.05 (2H, m), 3.25 (2H, m), 3.60 (2H, m), 3.65 (3H, s), 4.88 (1H, m), 7.20 (1H, t), 7.31 (1H, s), 7.45 (2H, m), 7.86 (1H, dd), 8.13 (1H, dd), 8.20 (1H, d). MS (ES): C27H29ClN4O4 requires 508; found 509.2 (M+H+).
