To a solution of palmitoyl-L-Ala-D-Glu(OH)OBzl (1)(1.84 g) in a mixture of tetrahydrofuran (20 ml) and chloroform (30 ml) were added N-hydroxysuccinimide (425 mg) and dicyclohexylcarbodiimide (728 mg). The reaction mixture was kept for 18 hours at room temperature and the precipitate was filtered off and washed with chloroform. The filtrate was concentrated in vacuo and the diisopropylether was added to the residue. The product was collected and dried to afford palmitoyl-L-Ala-D-Glu(OSu)OBzl (2)(170 g).
