2-Naphthylalanine → 2-Amino-4-(3-methoxycarbonyl-propyl)-imidazole-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

6-bromo-5-oxo-hexanoic acid methyl ester (2.30 g, 10.3 mmol), Boc-guanidine (4.92 g, 30.9 mmol),32 and Nal (3.07 g, 20.6 mmol) were dissolved in DMF (30 mL) and allowed to stir at room temperature. After 24 h the DMF was removed under reduced pressure and the residue was taken up in ethyl acetate (100 mL) and washed with water (3×50 mL) and brine (50 mL) before being dried (Na2SO4), filtered and evaporated to dryness. The resulting oil was purified by flash column chromatography (50-100% EtOAc/Hexanes) to obtain a yellow oil. Trituration of the viscous oil with cold hexanes (20 mL) produced a precipitate, which upon filtration yielded 18 (1.89 g, 65%) as a pale yellow solid. 1H NMR (400 MHz, CDCl3) δ 6.53 (s, 1H), 5.6 (br s, 2H), 2.41 (t, 2H, J=7.2 Hz), 2.37 (t, 2H, J=7.2 Hz), 1.93 (quint., 2H, J=7.2 Hz), 1.58 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 174.09, 150.11, 149.61, 138.39, 107.15, 84.81, 51.56, 33.65, 28.18, 27.68, 23.82; HRMS (ESI) calcd for C13H22N3O4 (MH)+284.1604, found 284.1606.

Provenance & Evidence