Citric Acid → HCID 53668274, compound

Participants

Reaction Steps

To a cold (0°) solution of N-tertiarybutoxycarbonyl-L-leucine (4 g, 15.1 mM), O-methyl-L-tyrosine t-butyl ester (3.8 g, 15.1 mM) and 1-hydroxybenzotriazole (2.43 g, 15.9 mM) in DMF (30 ml) was added N-methylmorpholine (1.61 g, 15.9 mM) and N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride (3.04 g, 15.9 mM). After stirring at 0° for 1 h the solution was allowed to warm to room temperature overnight. The reaction mixture was then concentrated in vacuo, dissolved in ethyl acetate, washed (water, 0.5 mole citric acid, brine, saturated aqueous sodium bicarbonate solution and brine), dried and evaporated in vacuo to give an oil. Chromatography on silica eluting with 25% ethyl acetate in hexane then gave the title compound as a foam (4.65 g); (Found: [m+1]+ =499.2803. C28H39N2O6 requires 499.2808); δ(CDCl3) 0.92 (6H, m, CH(CH3)3); 1.42 (9H, s, OC(CH3)3); 1.4-1.83 (3H, m, CH2CH(CH3)2); 3.03 (2H, m, CH2Tyr); 3.76 (3H, s, OCH3); 4.18 (1H, m,α-CH); 4.69 (1H, dd, J=7 and 15 Hz,α-CH); 5.12 (2H, s, CH2C6H5); 5.17 (1H, m, CONH); 6.43 (1H, m, CONH); 6.79 (2H, d, J=8 Hz, Tyr); 7.06 (2H, d, J=8 Hz, Tyr); 7.36 (5H, s, C6H5).

Provenance & Evidence