Hydrochloric Acid → [3-(3-Ethylcarbamoyl-propylcarbamoyl)-propyl]-carbamic acid tert-butyl ester

Participants

Reaction Steps

Hydrochloric acid (12%, 64 ml) was added to a cold solution of Boc-derivative 3 (21.1 g, 91.7 mmol) in MeOH (190 ml) and stirred overnight at room temperature. The next day additional acid (30 ml) was added and stirring was continued for another 10 h. The reaction mixture was filtered, washed with CHCl3, concentrated and dried in vacuo overnight. The product was suspended in DMF (300 ml) with DIEA (42 ml), cooled to 0° C. and a solution of Bt-derivative 2 (29 g, 90.5 mmol) in DMF (100 ml) was added into the reaction mixture. The cooling bath was removed and the stirring was continued overnight. The solvent and DIEA were removed in vacuo at 45° C., the residue was suspended in CHCl3/H2O mixture, washed with H2O, aq. KHSO4 (20%), H2O, aq. NaHCO3 (2 times with each), dried (Na2SO4), concentrated in vacuo, and triturated with petr. ether. Yield 22.32 g (78%). mp: 134-1350. 1H (CDCl3): 1.15 (t, J=7.27, 3H), 1.44 (s, 9H), 1.65-1.95 (m, 4H), 2.20-2.26 (m, 4H), 3.19 (q, J=6.15, 2H), 3.23-3.35 (m, 4H), 4.82 (bs, 1H), 6.40 (bs, 1H), 6.68 (bs, 1H). 13C (CDCl3): 14.77, 24.92, 25.66, 26.43, 28.38, 33.59, 33.84, 33.92, 34.35, 38.83, 39.66, 79.35, 156.56, 172.65, 173.12. ESI-MS: 338.2 (MNa+), 316.0 (MH+), 216.0 (MH+-Boc).

Provenance & Evidence