[CH2:1]([N:7]([CH2:13][C:14]([O:16]C)=[O:15])[CH2:8][C:9]([O:11]C)=[O:10])[CH2:2][CH2:3][CH2:4][C:5]#[CH:6].[OH-].[K+]>C1COCC1>[CH2:1]([N:7]([CH2:13][C:14]([OH:16])=[O:15])[CH2:8][C:9]([OH:11])=[O:10])[CH2:2][CH2:3][CH2:4][C:5]#[CH:6]To the obtained approximately 1.4 g dimethyl 2,2′-(hex-5-ynylazanediyl)diacetate was added 20 mL THF and 20 mL of 2 M KOH. The mixture was stirred overnight and monitored by TLC. The organic layer was separated, and the aqueous layer was quenched by addition of 20 mL of 2 M HCl. The solvent (H2O) was removed by rotary evaporation, and the resulting solid was dissolved into acetonitrile (ACN). The insoluble KCl salt was filtered, and the filtrate was concentrated by rotary evaporation. The final product of free acid was obtained as a greasy, transparent oil. Yield was quantitative. ESI-MS: [M+H]+ m/z 214.1.
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