[N:1]1[CH:6]=[CH:5][C:4]([CH2:7][CH2:8][N:9]2[CH2:14][CH2:13][C:12]3([CH2:19][CH2:18][CH:17]([CH2:20][C:21]([O:23]CC)=[O:22])[CH2:16][CH2:15]3)[CH2:11][CH2:10]2)=[CH:3][CH:2]=1>C(O)C.[OH-].[Na+].O>[N:1]1[CH:2]=[CH:3][C:4]([CH2:7][CH2:8][N:9]2[CH2:10][CH2:11][C:12]3([CH2:19][CH2:18][CH:17]([CH2:20][C:21]([OH:23])=[O:22])[CH2:16][CH2:15]3)[CH2:13][CH2:14]2)=[CH:5][CH:6]=1To a solution of 0.05 g (0.145 mmol) of the ester from Example 22 in 2 ml ethanol were added three drops of 2N aqueous sodium hydroxide solution. The mixture was heated at 70° C. for 3 h and diluted with 10 ml water. It was washed two times with dichloromethane, and the aqueous layer was adjusted to pH 7-8 with hydrochloric acid. After another extraction with dichloromethane the aqueous layer was concentrated under reduced pressure and the residue stirred with 20 ml of a mixture of ethanol/dichloromethane 9:1. Solids were removed by filtration, and the filtrate was concentrated in vacuo to leave the pure title acid.
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