[CH3:1][O:2][CH2:3][C@H:4]([CH3:51])[CH2:5][O:6][CH2:7][C:8]1[CH:13]=[CH:12][C:11]([C@@H:14]2[C@@H:19]([O:20][CH2:21][C:22]3[CH:23]=[CH:24][C:25]4[O:30][CH2:29][CH2:28][N:27]([CH2:31][CH2:32][CH2:33][O:34][CH3:35])[C:26]=4[CH:36]=3)[CH2:18][N:17]([S:37]([C:40]3[CH:45]=[CH:44][C:43]([CH3:46])=[CH:42][CH:41]=3)(=[O:39])=[O:38])[C@@H:16]([CH2:47][C:48](O)=[O:49])[CH2:15]2)=[CH:10][CH:9]=1.O1CCCC1.B>C1COCC1>[CH3:1][O:2][CH2:3][C@H:4]([CH3:51])[CH2:5][O:6][CH2:7][C:8]1[CH:13]=[CH:12][C:11]([C@@H:14]2[C@@H:19]([O:20][CH2:21][C:22]3[CH:23]=[CH:24][C:25]4[O:30][CH2:29][CH2:28][N:27]([CH2:31][CH2:32][CH2:33][O:34][CH3:35])[C:26]=4[CH:36]=3)[CH2:18][N:17]([S:37]([C:40]3[CH:45]=[CH:44][C:43]([CH3:46])=[CH:42][CH:41]=3)(=[O:38])=[O:39])[C@@H:16]([CH2:47][CH2:48][OH:49])[CH2:15]2)=[CH:10][CH:9]=1To a stirred solution of 1.0 mmol of [(2R,4R,5R)-4-[4-((S)-3-methoxy-2-methyl-propoxymethyl)-phenyl]-5-[4-(3-methoxy-propyl)-3,4-dihydro-2H-benzo[1,4]oxazin-6-ylmethoxy]-1-(toluene-4-sulfonyl)-piperidin-2-yl]-acetic acid (example 1g) in 4 ml of THF are added 2.2 mmol of borane tetrahydrofuran complex (1M in THF) at RT. The reaction mixture is stirred for 3 h, quenched with 60 ml of MeOH and concentrated under reduced pressure. The residue is purified by flash chromatography (SiO2 60 F) to afford the title compound which is identified based on its Rf-value.
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