A suspension of 16 g (0.058 mols) of γ-glutamylglutamic acid in 55 ml of water was dissolved in a 27-% sodium hydroxide aqueous solution until the pH reached 11, and 27 ml of acetone were added thereto. To the solution were added dropwise 12.6 g (0.058 mole) of lauroyl chloride over a period of 1 hour. When adding lauroyl chloride, the temperature was maintained at 10° C., and 27-% sodium hydroxide was added dropwise simultaneously to keep the pH at 11. After the completion of the addition of lauroyl chloride, the reaction solution was warmed at 30° C., and allowed to stand for 30 minutes. Subsequently, the pH was adjusted to 1 with the addition of conc. hydrochloric acid. The solid precipitate was separated by filtration, and dried to obtain 23.6 g of N-(N'-lauroyl-γ-glutamyl)glutamic acid in a yield of 89%. This solid was analyzed by infrared spectrophotometry. A peak diagnostic of an amide group was observed at 1,640 cm-1 and a peak diagnostic of a carboxyl group was observed at 1,730 cm-1, respectively. FAB mass spectrum: 459 (MH+).
