A mixture of 3-phthalimido-3-(3-cyclopentyloxy-4-methoxyphenyl)propionic acid (2.05 g, 5.00 mmol), 1,1'-carbonyldiimidazole (0.91 g, 5.5 mmol) and 4-dimethylaminopyridine (trace) in tetrahydrofuran (20 mL) was stirred for 1.5 hours under nitrogen at approximately 25° C. To the solution was added ammonium hydroxide (1.07 mL, 16.0 mmol, 28-30%) and stirring was continued for 1.5 hours. A small amount of solid forms during this time. The mixture was concentrated to half its volume and a white solid precipitated. The mixture was filtered, washed with a small amount of tetrahydrofuran, air dried, and dried in vacuo (60° C.,<1 mm) to afford 1.27 g of the product. The product was further purified by flash column chromatography (silica gel, 5% methanol/methylene chloride) and the resulting white solid was dried in vacuo (60° C., <1 mm) to afford 1 g (49%) of the product: mp 165°-166° C.; 1H NMR (CDCl3) δ 7.85-7.61 (m, 4H), 7.16-7.04 (m, 2H), 6.85-6.75 (m, 1H), 5.80 (dd, J=5.8, 10.4 Hz, 1H), 5.66 (br s, 1H), 5.54 (br s, 1H), 4.82-4.70 (m, 1H), 3.80 (s, 3H), 3.71 (dd, J=10.4, 15 Hz, 1H), 3.06 (dd, J=5.8, 15 Hz, 1H), 2.06-1.51 (m, 8H); 13C NMR (CDCl3) δ 171.8, 168.3, 149.8, 147.7, 133.9, 131.8, 131.3, 123.3, 119.9, 114.6, 111.8, 80.4, 56.0, 51.6, 37.9, 32.7, 24.1; Anal. Calcd for C23 H24N2O5. Theoretical: C, 67.63; H, 5.92; N, 6.86. Found: C, 67.25; H, 5.76; N, 6.68.
