[Li+].[OH-].[CH3:3][C:4]1[O:8][N:7]=[C:6]([C:9]([NH:11][C@H:12]2[C:20]3[C:15](=[CH:16][CH:17]=[C:18]([C:21]([O:23]C)=[O:22])[CH:19]=3)[CH2:14][CH2:13]2)=[O:10])[CH:5]=1>O.CO.C1COCC1>[CH3:3][C:4]1[O:8][N:7]=[C:6]([C:9]([NH:11][C@H:12]2[C:20]3[C:15](=[CH:16][CH:17]=[C:18]([C:21]([OH:23])=[O:22])[CH:19]=3)[CH2:14][CH2:13]2)=[O:10])[CH:5]=1LiOH (3.0 g, 42.66 mmol, 8 eq) in water (30 ml) was added dropwise to a cooled (0° C.) solution of (R)-methyl 3-(5-methylisoxazole-3-carboxamido)-2,3-dihydro-1H-indene-5-carboxylate (B-25) (1.6 g, 5.3 mmol, 1 eq) in MeOH:THF (1:1, 60 ml), and stirring was carried out for 5 h at RT. After monitoring by thin-layer chromatography, the reaction solution was concentrated under reduced pressure and the residue was taken up in water (50 ml), adjusted to pH 2 with KHSO4 and extracted with DCM (2×100 ml). The combined organic phases were washed with sat. NaCl solution (50 ml), dried over sodium sulfate and concentrated under reduced pressure. Yield: 59% (900 mg, 3.14 mmol).
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