Lithium hydroxide, monohydrate → (S)-2-(8-chloro-3-oxo-3,9-dihydro-1H-chromeno[2,3-c]pyrrol-2-yl)-3-cyclohexyl-propionic acid

A solution of (S)-2-(8-chloro-3-oxo-3,3a-dihydro-1H-chromeno[2,3-c]pyrrol-2-yl)-3-cyclohexyl-propionic acid methyl ester (1.5 g, 4.0 mmol) and lithium hydroxide monohydrate (0.22 g, 5.22 mmol) was stirred at 25° C. for 2 hours in tetrahydrofuran-water (3:1) mixture (50 mL). The reaction mixture was concentrated in vacuo to remove tetrahydrofuran, and the residue was acidified with 2N hydrochloric acid, and diluted with water. The resulting solution was extracted with ethyl acetate (3×). The combined organic layer was washed with brine and dried over anhydrous sodium sulfate. The solvent was removed in vacuo to afford (S)-2-(8-chloro-3-oxo-3,9-dihydro-1H-chromeno[2,3-c]pyrrol-2-yl)-3-cyclohexyl-propionic acid (1.2 g, 83.3%).