p-Toluenesulfonic acid → 3-Benzyl 4-ethyl 4-(but-3-enyl)-2,2-dimethyloxazolidine-3,4-dicarboxylate

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Reaction Steps

A solution of the ethyl 2-(benzyloxycarbonylamino)-2-(hydroxymethyl)hex-5-enoate 4 (820 mg, 2.55 mmol) in toluene (10 mL) was treated with 2,2-dimethoxy propane (2 mL) and 4-toluenesulfonic acid (100 mg). The mixture was heated under reflux for 1 h, cooled, concentrated and purified using a combiflash system (12 g silica gel column, eluting with 5-50% of ethyl acetate in heptanes) to give 3-benzyl 4-ethyl 4-(but-3-enyl)-2,2-dimethyloxazolidine-3,4-dicarboxylate (530 mg, 57%). 1H NMR (CDCl3) δ 7.36 (m, 5H), 5.75 (m, 1H), 4.51 (m, 4H), 4.06 (m, 4H) 2.08 (m, 4H), 1.65 (2 s, 6H), 1.13 (t, J=7.1 Hz, 3H). MS found for C20H27NO5 m/z [332 (M+1)].

Provenance & Evidence