To a suspension of (±)-(S*)-(3,5-dimethoxy-phenoxy)-((1S*)-1-phenyl-1,2,3,4-tetrahydro-isoquinolin-1-yl)-acetic acid (200 mg, 0.477 mmol, Example 1) in acetonitrile (5 ml) Hünig's base (327 μl, 1.91 mmol) followed by chlorotrimethylsilane (72 μl, 0.572 mmol) is added. The mixture is stirred at 55° C. for 3 h before ethyliodide (95 μl, 1.19 mmol) is added. Stirring at 55° C. is continued for another 16 h before water is added (about 200 μl). The solvent is removed under reduced pressure and the crude product is purified by prep. HPLC on Rp-C18 silica gel to furnish (±)-(S*)-(3,5-dimethoxy-phenoxy)-((1S*)-2-ethyl-1-phenyl-1,2,3,4-tetrahydro-isoquinolin-1-yl)-acetic acid (58 mg) as a white solid. LC-MS2: tR=4.20 min, [M+1]+=448.39, [M−1]−=446.34.
