To a mixture of Boc-L-Ala-D-Glu(OH)OMe (1) (1.94 g), L-Lys(ε-Z)-GlyOEt (2) (1.67 g) and 1-(4-chlorobenzenesulfonyloxy)-6-chlorobenzotriazole (1.72 g) in methylene chloride (100 ml) was added N-methylmorpholine (1.01 g) and the mixture was stirred for 2 days at room temperature. The reaction mixture was washed sccessively with 5% aqueous sodium bicarbonate, water, 5% hydrochloric acid and water and dried over magnesium sulfate. After evaporation of the solvent, the resulting crystalline mass was filtered and washed with ether, to give Boc-L-Ala-γ-D-Glu(α-OMe)-L-Lys(ε-Z)-GlyOEt (3) (1.34 g).
