p-Toluenesulfonic acid → 1-O-tert-butyl 2-O-methyl 5-methoxypyrrolidine-1,2-dicarboxylate

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Reaction Steps

To a solution of 5-hydroxy-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester, 2, (48.1 g, 196 mmol) in methanol (500 mL), is added p-toluenesulfonic acid (1.0 g, 5.8 mmol). Once consumption of the starting material is complete, the solvent is removed under in vacuo and the residue purified over silica (hexanes/ethyl acetate 75:25) to afford 42 g (83% yield) of the desired product as a clear oil. 1H-NMR (300 MHz, CDCl3): δ 5.334–5.142 (m, 1H), 4.36–4.24 (m, 1H), 3.75–3.72 (m, 3H), 3.44–3.36 (m, 3H), 2.45–1.71 (m, 4H), 1.51–1.42 (m, 9H); 13C-NMR (75.5 MHz, CDCl3): δ 200.16, 199.70, 173.31, 172.99, 154.28, 154.13, 153.98, 89.37, 89.27, 88.62, 88.41, 81.27, 81.04, 80.75, 80.54, 59.65, 59.33, 58.97, 58.84, 56.38, 56.14, 55.92, 55.79, 55.38, 55.00, 52.07, 51.99, 32.95, 32.29, 31.79, 31.14, 30.20, 28.35, 28.17, 27.11, 24.86, 21.06, 14.29; MS (ESI): m/e=282.07 (M+Na).

Provenance & Evidence