C([O:3][C:4](=[O:19])[CH2:5][C@H:6]1[CH2:18][CH2:17][N:9]2[C:10]3[C:15]([CH:16]=[C:8]2[CH2:7]1)=[CH:14][CH:13]=[CH:12][CH:11]=3)C.[OH-].[Na+].Cl>CO>[CH:14]1[CH:13]=[CH:12][CH:11]=[C:10]2[C:15]=1[CH:16]=[C:8]1[CH2:7][C@@H:6]([CH2:5][C:4]([OH:19])=[O:3])[CH2:18][CH2:17][N:9]12A solution of 17 g (63 mmol) of methyl alpha (R or S)-ethyl-6,7,8,9-tetrahydropyrido[1,2-a]indole-8(S)-acetate (diastereomers A+B) in 150 ml of methanol was treated with 130 ml of 2M sodium hydroxide and heated to reflux for 18 hours. The cooled solution was added to 150 ml of 4M hydrochloric acid and the resulting precipitate was filtered off and partitioned between 200 ml of dichloromethane and 100 ml of water. The organic phase was separated, dried over magnesium sulfate and evaporated to give 15 g of alpha (R or S)-6,7,8,9-tetrahydropyrido[1,2-a]indole-8(S)-acetic acid (diastereomers A+B) as a pale pink solid.
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