Hydrochloric Acid → N-(Methoxycarbonyl)-O-methyl-L-homoserine

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반응 단계

Piperidine (1.0 mL, 10 mmol) was added to a solution of (S)-2-(9H-fluoren-9-yl)methoxy)carbonylamino)-4-methoxybutanoic acid (0.355 g, 1 mmol) in DMF (3 mL), and the mixture was stirred at rt for 3 h. The volatiles were removed and the residue was partitioned between sat. NaHCO3 (aq.) (5 mL) and EtOAc (5 mL). The aqueous layer was further washed with EtOAc and Et2O. To the aqueous solution was added Na2CO3 (212 mg, 2.0 mmol) followed by methyl chloroformate (0.16 mL, 2.0 mmol) and the reaction mixture was stirred at rt for 16 h. The reaction mixture was acidified with 1 N HCl (aq.) until pH<7 and then extracted with EtOAc (2×10 mL). The combined organic layers were dried (Na2SO4), filtered and concentrated. The residue was purified by flash silica chromatography (EtOAc/hexanes, gradient from 20% to 70%) to yield (S)-4-methoxy-2-(methoxycarbonylamino)butanoic acid (Cap-194) (91.5 mg) as viscous colorless oil. LC-MS retention time=0.61 min; m/z 214 [M+Na]+. (Column: PHENOMENEX® Luna 3.0×50 mm S10. Solvent A=90% Water: 10% Methanol: 0.1% TFA. Solvent B=10% Water: 90% Methanol: 0.1% TFA. Flow Rate=4 mL/min. Start % B=0. Final % B=100. Gradient Time=3 min. Wavelength=220). 1H NMR (400 MHz, chloroform-d) δ ppm 7.41 (br. s., 1H), 5.74-6.02 (m, 1H), 4.32-4.56 (m, 1H), 3.70 (s, 3H), 3.54 (t, J=5.0 Hz, 2H), 3.34 (s, 3H), 1.99-2.23 (m, 2H).

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