To a solution of 3-cyclopentyl-2-(4-methanesulfonylphenyl)propionic acid (200 mg, 0.67 mmol) in a mixture of dry methylene chloride (5 mL) and dry DMF (1 mL) were added HOBT (20 mg) and DCC (155 mg, 0.75 mmol), and the mixture was stirred at room temperature for 2 h. A solution of (2-amino-5-methyl-thiazol-4-yl)-acetic acid ethyl ester (220 mg, 0.78 mmol) and DIPEA (135 μl, 102 mg, 0.79 mmol) in dry DMF (1 mL) was added to the reaction mixture and stirring was continued for 18 h at room temperature. The mixture was evaporated in vacuo and the residue purified on a silica gel column (heptan:ethyl acetate (7:3)) to give {2-[3-cyclopentyl-2-(4-methanesulfonyl-phenyl)-propionylamino]-5-methyl-thiazol-4-yl}-acetic acid ethyl ester. Yield: 120 mg (37%). 1H-NMR (CDCl3): δ 8.86 (broad s, 1H), 7.91 (d, 2H), 7.52 (d, 2H), 4.14 (q, 2H), 3.66 (t, 1H), 3.57 (s, 2H), 3.07 (s, 3H), 2.32 (s, 3H), 2.25-2.18 (m, 1H), 1.93-1.86 (m, 1H), 1.81-1.43 (m, 7H), 1.24 (t, 3H), 1.16-1.06 (m, 2H); HPLC-MS: m/z=480 (M+1); Rt=4.09 min.
