To a 250 mL round bottomed flask equipped with a magnetic stirrer and a nitrogen inlet were added 2.19 g of tert-butyl (2R,3S,5S)-oxo-2,3-diphenyl-5-(3-(3-pentyl)benzyl)-4-morpholinecarboxylate and 45 mL of anhydrous CH2Cl2. The solution was cooled to 0° C. and was treated with 3.5 mL of TFA. The solution was allowed to warm to RT and was stirred under nitrogen. After 5 h, tlc (SiO2, 9:1 hexane:EtOAc) indicated a trace of starting material and a major new component at Rf=0.42. The reaction mixture was poured into 150 mL of 6% aqueous NaHCO3 and stirred for several minutes. The phases were separated and the aqueous portion was extracted with 3 additional 40 mL portions of CH2Cl2. The extracts were combined with the original CH2Cl2 solution and washed with 5% aqueous NaHCO3 (3×60 mL). The solution was dried over anhydrous MgSO4 and concentrated to give a light tan solid. This material was purified by flash chromatography on silica gel (85:15 hexane:EtOAc) to afford 1.47 g (84%) of (2R,3S,5S)-oxo-2,3-diphenyl-5-(3-(3-pentyl)benzyl)morpholine as a white crystalline solid. An analytical sample was prepared by recrystallization from EtOH-H2O. Melting point, 96-97° C.
