isobutyl (4S)-4-benzyl-5-oxo-2-imidazolidinepropanoate → (3S)-3-Benzyl-2,5-dioxohexahydro-1H-pyrrolo[1,2-a]imidazole

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Reaction Steps

A solution of isobutyl (4S)-4-benzyl-5-oxo-2-imidazolidinepropanoate (2.3 g, 7.33 mmol) in toluene (100 ml) was refluxed for 8 days. After evaporation of the solvent, the residue was chromatographed over silica gel (dichlorometane-methanol 9:1). The appropriate fractions were collected and evaporated; the residue was triturated with diethyl ether to afford 850 mg (50%) of the title compound, m.p. 141°-145° C. NMR (CDCl3): deltaH =7.25 (s, 5H, PhH); 7.02 (b.s., 1H, NH); 4.52 (t, J=4.5 Hz, 1H, PhCH2CH); 4.37 (t, J=5 Hz, 1H, NCHNH); 3.13 (d, J=4.5 Hz, 2H, PhCH2); 2.80-1.6 (c.a., 4H, CH2CH2). MS (E.I., 70 eV, 1.5 mA) m/z 230 (M+), 139 (M--C7H7)+, 91 (C7H7)+, 84 (C4H6NO)+.

Provenance & Evidence