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With benzotriazol-1-ol; In dichloromethane; ethyl acetate;
D. N-t-butyloxycarbonyl-L-alanyl-L-prolyl-L-proline benzyl ester N-t-butyloxycarbonyl-L-alanyl-L-proline (4.3 g, 15 m mole), L-proline benzyl ester hydrochloride (3.7 g, 15.3 m mole) and HOBt (2.0 g, 15 m mole) were dissolved in methylene dichloride (40 ml). WSC (2.8 ml) was added dropwise to the above mixture while cooling to -15 C. and stirring. The reaction was carried out for 3 hours at a temperature of not more than 0 C., and then overnight at room temperature. The solvent was removed by distillation under reduced pressure leaving a residue. The residue was dissolved in ethyl acetate, and washed with 1N hydrochloric acid, water, 5% sodium bicarbonate and water, in order. The mixture was dried over anhydrous sodium sulfate. The thus obtained solution was distilled under reduced pressure leaving a residue. The residue was crystallized with a mixture of ethyl acetate and n-hexan to give a crystal of N-t-butyloxycarbonyl-L-alanyl-L-prolyl-L-proline benzyl ester (6.3 g, 88.7%) having melting point of 143 to 145 C. and specific rotatory power of [alpha]D25 =-131.0 (C-1, chloroform).
88.7%
With benzotriazol-1-ol; In dichloromethane; ethyl acetate;
D. N-t-butyloxycarbonyl-L-alanyl-L-prolyl-L-proline benzyl ester N-t-butyloxycarbonyl-L-alanyl-L-proline (4.3 g, 15 m mole), L-proline benzyl ester hydrochloride (3.7 g, 15.3 m mole) and HOBt (2.0 g, 15 m mole) were dissolved in methylene dichloride (40 ml). WSC (2.8 ml) was added dropwise to the above mixture while cooling to -15 C. and stirring. The reaction was carried out for 3 hours at a temperature of not more than 0 C., and then overnight at room temperature. The solvent was removed by distillation under reduced pressure leaving a residue. The residue was dissolved in ethyl acetate, and washed with 1N hydrochloric acid, water, 5% sodium bicarbonate and water, in order. The mixture was dried over anhydrous sodium sulfate. The solvent thus obtained solution was distilled under reduced pressure leaving a residue. The residue was crystallized with a mixture of ethyl acetate and n-hexan to give a crystal of N-t-butyloxycarbonyl-L-alanyl-L-prolyl-L-proline benzyl ester (6.3 g, 88.7%) having melting point of 143 to 145 C. and specific rotatory power of [alpha]D25 =-131.0 (C=1, chloroform).
88.7%
With benzotriazol-1-ol; In dichloromethane; ethyl acetate;
D. N-t-butyloxycarbonyl-L-alanyl-L-prolyl-L-proline benzyl ester N-t-butyloxycarbonyl-L-alanyl-L-proline (4.3 g, 15 m mole), L-proline benzyl ester hydrochloride (3.7 g, 15.3 m mole) and HOBt (2.0 g, 15 m mole) were dissolved in methylene dichloride (40 ml). WSC (2.8 ml) was added dropwise to the above mixture while cooling to -15 C. and stirring. The reaction was carried out for 3 hours at a temperature of not more than 0 C., and then overnight at room temperature. The solvent was removed by distillation under reduced pressure. The residue was dissolved in ethyl acetate, and washed with 1N hydrochloric acid, water, 5% sodium bicarbonate and water, in order. The mixture was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was crystallized with a mixture of ethyl acetate and n-hexan to give a crystal of N-t-butyloxycarbonyl-L-alanyl-L-prolyl-L-proline benzyl ester (6.3 g, 88.7%) having melting point of 143 to 145 C. and specific rotatory power of [alpha]D25 =-131.0 (C=1, chloroform).
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