A mixture of 1-(1-hydroxyethyl)-3-oxocyclopentanecarboxylic acid (3.54 g, 20.6 mmol), 1-hydroxy-7-azabenzotriazole (4.14 g, 30.9 mmol), and EDC (5.92 g, 30.9 mmol) in 70 mL of DCM was stirred at rt for 10 min then 1-[2-tert-butoxy-5-(trifluoromethyl)phenyl]methanamine (5.08 g, 20.6 mmol) was added in 10 mL of DCM. The resulting mixture was stirred at rt for 50 min, then was diluted with DCM and washed with water followed by brine. The organic layer was dried over anhydrous MgSO4, filtered, and concentrated. Purification by MPLC (silica, 85% ethyl acetate/hexanes) provided N-[2-tert-butoxy-5-(trifluoromethyl)benzyl]-1-(1-hydroxyethyl)-3-oxocyclopentanecarboxamide as a mixture of threo and erythro enantiomer pairs.
