A mixture of 200 mg (0.5 mmol) of [4-[[3-(2-amino-2-oxoethyl)-2-ethyl-1-(phenylmethyl)-1-H-indol-5-yl]oxy]butanoic acid ethyl ester and 4 mL of 1N NaOH in 10 mL of EtOH was stirred for 1.5 hours, diluted with water and extracted with EtOAc. The aqueous layer was made acidic to pH 5 with 1N HCl, extracted with EtOAc, the EtOAc solution washed with brine and dried (MgSO4). The solvent was evaporated at reduced pressure, the residue stirred with ether/MeOH and the insoluble material filtered to give 120 mg (61% yield) of [4-[[3-(2-amino-2-oxoethyl)-2-ethyl-1-(phenylmethyl)-1-H-indol-5-yl]oxy]butanoic acid, mp, 196°-199° C.
