A solution of 1,1-dimethylethyl [[(5S)-2-oxo-3-[1,2,3,4-tetrahydro-6-isoquinolinyl]-5-oxazolidinyl]methyl]carbamate (Example 6, Step 2, 347 mg, 0.999 mmol) and triethylamine (0.21 mL, 1.50 mmol) in dry CH2Cl2 at 0° C. under N2 is treated with benzyloxyacetyl chloride (0.19 mL, 1.20 mmol), and the resulting mixture is stirred at 0° C. for 1 hr and then allowed to warm to ambient temperature. The reaction mixture is then diluted with CH2Cl2 (20 mL), washed with H2O (10 mL) and brine (10 mL), dried over Na2SO4 and concentrated under reduced pressure. The residue is chromatographed on a Flash 40S silica gel (40 g, 32-63 μm) cartridge, eluting with a gradient of MeOH/CH2Cl2 (1/99-2/98), and those fractions with an Rf=0.72 by TLC (MeOH/CHCl3, 10/90) are pooled and concentrated to give 425 mg (86%) of the title compound as an amorphous, glassy solid. MS (ESI+) for C27H33N3O6 m/z 496 (M+H)+.
