tert-Butyl Formate → (1R,4S)-4-[(tert-Butoxycarbonyl)amino]-1-[(3R)-tetrahydrofuran-3-yl]cyclopent-2-ene-1-carboxylic acid

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Reaction Steps

To a solution of methyl (1R,4S)-4-[(tert-butoxycarbonyl)amino]-1-[(3R)-tetrahydrofuran-3-yl]cyclopent-2-ene-1-carboxylate (1.60 g, 5.14 mmol) in tetrahydrofuran (27.8 mL), methanol (27.8 mL) and water (6.0 mL) was added lithium hydroxide monohydrate g, 8.25 mmol). The pink mixture was heated to reflux for 18 h. The organic solvents were removed in vacuo and the aqueous layer was extracted once with ether and then acidified slowly with 6 M HCl until the pH reached 3-4. The resulting suspension was extracted with CH2Cl2 three times. The combined organic layers were dried over MgSO4, filtered and concentrated to give the product as a mixture of two cis/trans isomers (1.59 g) as a light yellow solid. MS calculated for C15H24NO5: (M+H) 298.2; found 198.2 (M+H-Boc).

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