A mixture of (S)-1-carboxymethyl-3-(5-chloroindole-2-carbonylamino)-3,4-dihydrocarbostyril (Example 10) (6 mg) in 1.0 M borane in tetrahydrofuran solution (2 mL) under argon was stirred at 35° C. for 3 h. After cooling to room temperature, 1.0 M aqueous hydrochloric acid (10 mL) and ethyl acetate (10 mL) were added. This mixture was stirred for 3 h before the layers were separated. The organic phase was washed with water (10 mL three times) and evaporated under vacuum. The residue was chromatographed on reverse phase preparative HPLC to isolate the title compound (1.1 mg) and the over-reduction product (S)-1-(2-hydroxyethyl)-3-(5-chloroindole-2-carbonylamino)-1,2,3,4-tetrahydroquinoline (0.9 mg). Title compound HPLC/MS [M+H]+, 384.
