Dicyclohexylcarbodiimide → 1,2,3-Benzotriazol-1-yl 4[[(tert-Butyloxy)carbonyl]-amino]-1-methylimidazole-2-carboxylate

Participants

Reaction Steps

The Boc-pyrrole-acid 8 (31 g, 129 mmol) was dissolved in 500 ml DMF and hydroxybenzotriazole (17.4 g, 129 mmol) was added followed by DCC (34 g, 129 mmol). The reaction was allowed to stir for 24 hours and then filtered dropwise into a well stirred solution of 5 liters of water (0° C.). The precipitate was allowed to sit for 15 minutes at 0° C. and then collected by filtration. The wet cake was dissolved in 500 ml of dichloromethane, washed with 200 ml brine, and added slowly to a stirred solution of petroleum ether at −20° C. After 4 hours at −20° C. the precipitate was collected by vacuum filtration and dried in vacuo to give (39 g, 85% yield) of a finely divided white powder. (A yellowish impurity may be observed, which can be removed by flash chromatography (acetone:dichloromethane), followed by precipitation in petroleum ether). TLC (7:2 benzene/ethyl acetate v/v) Rf 0.6; 1H NMR (DMSO-d6) δ9.43 (s, 1H), 8.12 (d, 1H, J=8.4 Hz), 7.80 (d, 1H, J=8.2 Hz), 7.64 (t, 1H, J=7.0 Hz), 7.51 (m, 2H), 7.18 (s. 1H), 3.83 (s, 3H), 1.45 (s. 9H); 13C NMR (DMSO-d6) δ156.5, 153.3, 143.2, 129.6, 129.2, 125.7, 125.2, 124.6, 120.3, 112.8, 110.3, 109.8, 79.5, 36.8, 28.6.

Provenance & Evidence