To a solution of 4-{[(1′R,2′R)-1′-(L-leucyloxy)-1′,3′-dihydro-1H,2′H-2,2′-biinden-2′-yl]methyl}benzoic acid (24, 130 mg, 0.26 mmol), Et3N (78 mg, 0.78 mmol) and 2-amino ethanol (24 mg, 0.39 mmol) in DCM (5 mL), was added T3P (0.33 mL, 50 wt % solution in ethyl acetate, 0.52 mmol) and then stirred at room temperature for 12 h. The reaction mixture was quenched with water (25 mL) and extracted with DCM (3×25 mL). The separated organic layer was washed with brine (25 mL), dried over anhydrous Na2SO4 and evaporated under reduced pressure. The residue was purified by CombiFlash using 10% methanol in chloroform as an eluent to yield 70 mg (54%) of the title compound as an off white solid.
