To a suspension of (±)-(S*)-(3,5-dimethoxy-phenoxy)-((1S*)-1-phenyl-1,2,3,4-tetrahydro-isoquinolin-1-yl)-acetic acid (60 mg, 0.143 mmol, Example 1) in THF (5 ml) Hünig's base (122 μl, 0.715 mmol) followed by chlorotrimethylsilane (22 μl, 0.172 mmol) is added at 5° C. The mixture is stirred at 55° C. for 3 h before phenylacetylchloride (29 μl, 0.215 mmol) is added. Stirring is continued at rt for 2 h before water (approx. 200 μl) is added. The mixture is diluted with DCM, washed twice with 2 N aq. HCl. The organic phase is dried over Na2SO4 and evaporated. The crude product is purified by prep. HPLC on Rp-C18 silica gel to give (±)-(S*)-(3,5-dimethoxy-phenoxy)-((1S*)-1-phenyl-2-phenylacetyl-1,2,3,4-tetrahydro-isoquinolin-1-yl)-acetic acid (36 mg) as a white powder. LC-MS1: tR=0.98 min, [M+1]+=538.13.
