3-[4-(Spiro[5.5]undec-3-ylaminomethyl)benzoylamino]propionic acid ethyl ester was prepared by reductive alkylation of 3-(4-aminomethyl-benzoylamino)propionic acid ethyl ester with spiro[5.5]undecan-3-one. 3-[4-(Spiro[5.5]undec-3-ylaminomethyl)benzoylamino]propionic acid ethyl ester (200 mg, 499 μmol) was dissolved in acetonitrile (5 mL) and diisopropylethylamine (170 μL) and cooled on an ice bath. Commercially available 3-fluoro-5-(trifluoromethyl)benzoylchloride (136 mg, 602 μmol) dissolved in acetonitrile (5 mL) was added dropwise. The reaction was complete within one hour as shown by HPLC. The solvent was evaporated and water (10 mL) was added to the residue followed by saturated sodium bicarbonate (10 mL). The product was extracted using ethyl acetate (2×50 mL). The combined ethyl acetate extracts were washed with water (20 mL) and brine (20 mL). Drying the organic phases over MgSO4 and evaporation of the solvent afforded 3-(4-{[(3-fluoro-5-trifluoromethylbenzoyl)spiro[5.5]undec-3-yl-amino]methyl}benzoylamino)propionic acid ethyl ester (295 mg) which was hydrolyzed using sodium hydroxide to afford the title compound.
