Dissolve racemic 4-[3′,5′-dichloro-4′-(1-cyclohexyl-2-oxo-pyrrolidin-3-ylmethyl)-biphenyl-4-carbonyl]-piperazine-1-carboxylic acid tert-butyl ester (0.40, 0.65 mmol) in dioxane (20 mL), add 4N hydrochloric acid in dioxane (10 mL) and stir 30 min to obtain an orange residue in reaction vessel. Concentrate under vacuum, dilute residue with water (10 mL) and add potassium cyanate (0.55 g, 0.68 mmol). Stir the reaction at room temperature to obtain a white precipitate. Filter off solid and wash with water. Dissolve the solid in dichloromethane and concentrate under vacuum to yield a clear foam. Use resin bound solid phase acidic media (SCX) to remove residual starting material and obtain 0.168 g (46%) of product as a white solid: MS (m/z): 557 (M+).
