[CH:1]1([N:5]([CH3:13])[CH2:6]/[CH:7]=[CH:8]/[C:9]([O:11]C)=[O:10])[CH2:4][CH2:3][CH2:2]1.O[Li].O.[ClH:17]>C1COCC1.O>[ClH:17].[CH:1]1([N:5]([CH3:13])[CH2:6]/[CH:7]=[CH:8]/[C:9]([OH:11])=[O:10])[CH2:2][CH2:3][CH2:4]1To a solution of (E)-methyl 4-(cyclobutyl(methyl)amino)but-2-enoate (20) (1.47 g, 8 mmol) in THF/H2O (8 mL/2 mL) was added LiOH.H2O (730 mg, 16 mmol). The reaction mixture was stirred at RT overnight, then acidified with 1N HCl to pH=1 and concentrated in vacum to afford (E)-4-(cyclobutyl(methyl)amino)but-2-enoic acid hydrochloride salt (21) (2.31 g, 97%, mixed with LiCl) as a white solid which was used in the next step without purification. LC-MS (ESI): m/z (M+1) 170.2.
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