[CH3:1][C:2]([CH3:9])([CH:7]=O)[C:3]([O:5][CH3:6])=[O:4].[C:10]([N:17]1[CH2:22][CH2:21][NH:20][CH2:19][CH2:18]1)([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11].[BH-](OC(C)=O)(OC(C)=O)OC(C)=O.[Na+]>C(Cl)Cl>[CH3:6][O:5][C:3](=[O:4])[C:2]([CH3:1])([CH3:9])[CH2:7][N:20]1[CH2:19][CH2:18][N:17]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:22][CH2:21]1A solution of 567 (0.57 mmol, crude in 25 ml of DCM) and 1-Boc-piperazine (1.175 g, 6.31 mmol) in DCM (50 ml) was stirred for 1 h at rt under nitrogen, then cooled down to 0° C. To the cold solution NaBH(OAc)3 (4.22 g, 18.93 mmol) was added in one portion. The reaction mixture was stirred at 0° C. for 1 h, then at rt overnight, quenched by addition of water, stirred for 1 h and slowly neutralyzed with a saturated aqueous solution of sodium bicarbonate (pH=7-8). The alkaline solution was extracted with DCM. The organic extract was dried over anhydrous magnesium sulfate, filtered and concentrated. The residue was purified by Biotage (Snap 25 g cartridge, MeOH/DCM: 0/100 to 10/90 over 30 CV), to afford the desired product 568 (1.137 g, 3.79 mmol, 60% yield) as colorless oily liquid. MS (m/z): 301.3 (M+H).
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