100% |
With 2,3,4-lutidine; 1-hydroxy-7-aza-benzotriazole; diisopropyl-carbodiimide; In N,N-dimethyl-formamide; at 20℃; for 3h;Product distribution / selectivity; |
A solution of Boc-D-Leu-OH (150 mg, 0.649 rnmol), 9-fluorenylmethyl carbazate (164.9 mg, 0.649 mmol), HOAt (88.3 mg, 0.649 mmol), and collidine (428.5 muL, 3.243 mmol) in DMF (1 mL) was treated with DIC (200.8 muL, 1.297 mmol), and stirred at room temperature under nitrogen for 3 hours. The reaction mixture was diluted with ethyl acetate (25 mL), washed consecutively with 10percent citric acid (3 x 25 mL), 10percent NaHCO3 (3 x 25 mL), water (25 mL), and saturated NaCl (25 mL), dried ( MgSO4), filtered, and concentrated under reduced pressure to give the title compound as a colorless solid. (302 mg, 100percent). 1H NMR (CDCl3): delta 8.21 (s, IH), 7.74 (d, J= 7.8 Hz, 2H), 7.57 (d, J= 7.8 Hz, 2H), 7.38 (t, J= 7.5 Hz, 2H), 7.29 (t, J= 7.5 Hz, 2H), 6.79 (s, IH), 4.85 (s, IH), 4.43 (d, J= 7.2 Hz, 2H), 4.18 (s, IH), 3.96 (s, IH), 1.72 (m, 2H), 1.43 (s, 9H), 1.25 (m, IH), 0.94 (d, J= 6.6 Hz, 3H), 0.92 (d, J= 6.6 Hz, 3H). MS: m/e 368.3 [M+H-Boc] (35percent), 490.2 [M+Na] (100percent). |
100% |
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A solution of Boc-D-Leu-OH (134 mg, 0.536 mmol), HOAt (73 mg, 0.54 mmol) and TMP (0.87 mL, 2.7 mmol) in anhydrous DMF (2 mL) was treated with DIC (135 mg, 1.07 mmol), and stirred at ambient temperatures under nitrogen for 20 minutes. The solution was treated with 9-fluorenylmethyl carbazate (136 mg, 0.536 mmol) and stirred for 5 hours. The solution was diluted with dichloromethane (20 mL), washed consecutively with 10percent citric acid (3 X 20 mL), saturated NaHCO3 (20 mL), and saturated NaCl (20 mL), dried (MgSO4), filtered, and concentrated to give crude title compound as a viscous oil (271 mg, 108percent). MS (ESI): 368.3 (95, M+H), 490.2 (100, M+Na). |