13012-38-9

98-78-2

13012-38-9

Preparation of Example 1-(R)-3-oxocyclopentanecarboxylic acid (Compound 2): 3-oxo-1-cyclopentanecarboxylic acid (Compound 1, 57 g, 445.3 mmol) was dissolved with L-leucine (193.2 g, 489.8 mmol) in water (1.036 L) and heated to reflux until the solution clarified. The reaction mixture was cooled to room temperature, the precipitated crystals were collected by filtration, washed with water and dried. The resulting crystals were recrystallized three times by passing through water (500 mL) to give (R)-3-oxocyclopentanecarboxylic acid leucine salt. The product was analyzed by chiral HPLC and the enantiomeric excess (ee) was 99.71%.