4-Methylmorpholine → Z-Leu-Asp(OtBu)-Leu-Ala-CH2Cl

Participants

Reaction Conditions

Reaction Steps

Boc-Ala-CH2Cl (2 g) in 5 equiv of HCl in dioxane was stirred at room temp for 1 h. After removal of solvent, the residue was triturated with diethyl ether to give crude H-Ala-CH2Cl (1.41 g). The Z-Leu-Asp(OtBu)-Leu-OH (2.68 g) and N-methylmorpholine (0.54 mL) were dissolved in ThF (25 mL), the cooled to −20° C. Isobutyl chloroformate (0.64 mL) was added to generate the mixed anhydride, which was transferred to the H-Ala-CH2Cl (1.41 g in 10 mL of DMF) solution at −20° C. The resulting mixture was allowed to come to room temp and reaction was completed in 3 h. The salt was removed by filtration. The filtrate was concentrated, redissolved in ethyl acetate (100 mL). The solution was washed with 0.2 N HCl, 5% NaHCO3, sat. NaCl; dried over Na2SO4, filtered, and concentrated to yield crude solid of 3.19 g. The crude Z-Leu-Asp(OtBu)-Leu-Ala-CH2Cl was purified by Sephadex IMO column chromatography.

Provenance & Evidence