To a solution of 0.10 g 6-(2-chloro-phenyl)-5-pyrrolidin-1-yl-pyrazine-2-carboxylic acid in 3.0 ml of DMF is added at room temperature 0.082 g 1,1′-carbonyl-diimidazole, 0.22 ml N-ethyldiisopropylamine and 0.057 g (1R,2R)-2-amino-cyclohexanol hydrochloride and stirred for 72 hours. To the mixture is added citric acid 10% solution and ethyl acetate. The organic layer is washed with sodium bicarbonate 10% solution and sodium chloride saturated solution. The organic layer is separated and dried over sodium sulfate and evaporated at the rotary evaporator. The residue is purified by chromatography on silica gel with heptane/ethyl acetate 40/60 to yield 0.055 g of the title compound as white solid, MS (ISP) 401.3 (M+H)+.
