Pyridine → 3-[Bis-(4-methoxy-phenyl)-phenyl-methoxymethyl]-4-hydroxy-pyrrolidine-1-carboxylic Acid Benzyl Ester

Referring to scheme 18, compound 74 (4.39 g, 17.5 mmol) was co-evaporated with anhydrous pyridine three times and then dissolved in pyridine (30 mL). To this solution dimethylamino pyridine (0.213 g, 1.75 mmol) and DMT-Cl (6.22 g, 18.4 mmol, 1.05 equiv.) were added at room temperature. The reaction mixture was stirred at room temperature for 16 h. The excess DMT-Cl was quenched by the addition of methanol (10 mL). The solution was dried under reduced pressure. To the residue was suspended in ethyl acetate (300 mL) and washed with saturated bicarbonate solution, brine and water. The organic layer was dried over anhydrous sodium sulfate, filtered and evaporated. The crude product was obtained after removal of the solvent. Upon purification over silica gel using 3% MeOH/DCM compound 75 (8.46 g, 87%) was obtained as white foamy solid.