Cl.[CH2:2]([O:4][C:5](=[O:8])[CH2:6][NH2:7])[CH3:3].C(N(CC)CC)C.[C:16]([O:20][C:21]([NH:23][C@H:24]([C:27](O)=[O:28])[CH2:25][Cl:26])=[O:22])([CH3:19])([CH3:18])[CH3:17].C1(N=C=NC2CCCCC2)CCCCC1>C(Cl)(Cl)Cl>[CH2:2]([O:4][C:5](=[O:8])[CH2:6][NH:7][C:27](=[O:28])[C@H:24]([CH2:25][Cl:26])[NH:23][C:21]([O:20][C:16]([CH3:17])([CH3:19])[CH3:18])=[O:22])[CH3:3]
To a solution of 0.28 g (2 mmol) of glycine ethyl ester hydrochloride and 0.28 mL (2 mmol) of triethylamine in 10 mL of chloroform, 0.52 g (2 mmol) of N-(tert-butoxycarbonyl)-3-chloro-L-alanine in 6 mL of chloroform and 0.42 g (2 mmol) of dicyclohexylcarbodiimide were added at 0° C. The reaction mixture was stirred for 16 hours at room temperature. The resultant precipitate was removed by filtration and the filtrate was washed successively with 0.5N hydrochloric acid, water and 3% aqueous sodium bicarbonate, then was dried over anhydrous sodium sulfate. Removal of the solvent left a crystalline residue which was recrystallized from a mixture of ethyl acetate and n-hexane to give 0.415 g (60%) of the pure product melting at 71.5-72.0° C. The identity of the product, which has the structural formula ##STR73## was confirmed by IR and NMR analyses.
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