Lithium hydroxide, monohydrate → (S)-2-((tert-butoxycarbonyl)amino)-3-(cyclopent-1-en-1-yl)propanoic acid

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Reaction Steps

To a solution of (S)-methyl 2-(tert-butoxycarbonylamino)-3-cyclopentenylpropanoate (62 g, 0.23 mol) in water/methanol (900 mL, 2:1) was added lithium hydroxide hydrate (19.3 g, 0.460 mol). The reaction mixture was stirred at ambient temperature overnight and then concentrated to remove the majority of methanol. The residue was washed with DCM (400 mL) and the aqueous phase was acidified with diluted HCl to pH=3-4. The resulting mixture was extracted with DCM (300 mL×3). The organic layers were combined and concentrated to afford (S)-2-(tert-Butoxycarbonylamino)-3-cyclopentenylpropanoic acid (56 g, 95% yield) as viscous oil, which was used in the next step without further purification. 1H NMR (300 MHz, CDCl3): δ 10.47 (br. s, 1H), 5.52 (br. s, 1H), 4.98 (d, J=8.1 Hz, 1H), 4.40-4.44 (m, 1H), 2.50-2.70 (m, 2H), 2.25-2.34 (m, 4H), 1.79-1.93 (m, 2H), 1.45 (s, 9H).

Provenance & Evidence