Cl.[C:2]([C:4]1[CH:17]=[CH:16][C:7]([CH2:8][N:9]2[C:13]([CH:14]=O)=[CH:12][N:11]=[CH:10]2)=[CH:6][CH:5]=1)#[N:3].[C:18](O)(=O)[CH3:19].[C:22]([BH3-])#[N:23].[Na+].CCO[C:29]([CH3:31])=O>CO.C1COCC1>[C:2]([C:4]1[CH:17]=[CH:16][C:7]([CH2:8][N:9]2[C:13]([CH2:14][NH:9][C@@H:13]([CH2:29][CH2:31][CH2:18][CH3:19])[CH2:12][NH:23][C:22]3[CH:7]=[CH:6][CH:5]=[C:4]([CH3:2])[C:17]=3[CH3:16])=[CH:12][N:11]=[CH:10]2)=[CH:6][CH:5]=1)#[N:3]
Through a solution of the product from Step 1 (533 mg, 1.47 mmol) in 20 mL of EtOAc at 0° C. was bubbled HCl gas. The saturated solution was warmed to room temperature and stirred for 40 minutes, then concentrated in vacuo. To a solution of this amine salt in 6 mL of 1:1 MeOH/THF at 0° C. was added the aldehyde from Step E (325 mg, 1.54 mmol) and 0.05 mL of acetic acid. After one hour, sodium cyanoborohydride was added (97 mg, 1.54 mmol), and the solution was allowed to warm to room temperature overnight. After ~16 hours, the reaction was poured into EtOAc, washed with sat. aq. NaHCO3 and brine, dried (Na2SO4), filtered, and concentrated in vacuo. The resulting product was purified by silica gel chromatography (1-2% MeOH/CHCl3). A portion of this was taken up in EtOAc/Et2O and treated with excess HCl gas, then stripped to provide the titled compound.
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