Dicyclohexylamine → N-Benzyloxycarbonyl-beta-tert-butyl-L-aspartyl-L-leucyl-Nepsilon-tert-butyloxycarbonyl-L-lysine

Participants

Reaction Steps

A solution of Z-Asp(OtBu)-OSu (115.6 g; 0.275 mol) in DMF (1.16 L) was stirred at 0° in a 3 L, 3-necked round bottom flask fitted with a mechanical stirrer and thermometer. The H-Leu-Lys(Boc)-OH (89.86 g; 0.250 mol) was added followed by Et3N (35.2 mL; 0.25 mol). The reaction mixture was stirred at 0° for 0.5 h and at 25° for 1.5 h. Additional Et3N (17 mL) was added (to maintain pH 8) and the reaction mixture stirred at 25° for 20 h. The reaction mixture was evaporated, dissolved in EtOAc (3 L), washed with 1M citric acid (3×1 L), H2O (3×1 L), dried (MgSO4) and evaporated in vacuo. The residual paste was dissolved in anhydrous ether (5 L) and stirred magnetically while DCHA (53.5 mL; 0.268 mol) was added slowly. After standing in the cold room (20 h) the white salt was collected and washed with anhydrous ether (2×0.5 L) and petroleum ether (2×0.5 L). Yield: 177 g (84%); m.p. 173°-174°; [α]D25 -12.57° (c 1, MeOH).

Provenance & Evidence