[NH2:1][C@H:2]([C:7]([OH:9])=[O:8])[CH2:3][C:4](=[O:6])[NH2:5].[C:10]1([S:20](Cl)(=[O:22])=[O:21])[C:19]2[C:14](=[CH:15][CH:16]=[CH:17][CH:18]=2)[CH:13]=[CH:12][CH:11]=1.Cl>O.[OH-].[Na+].O1CCCC1>[C:4]([CH2:3][C@H:2]([NH:1][S:20]([C:10]1[C:19]2[C:14](=[CH:15][CH:16]=[CH:17][CH:18]=2)[CH:13]=[CH:12][CH:11]=1)(=[O:22])=[O:21])[C:7]([OH:9])=[O:8])(=[O:6])[NH2:5]132.12 g (1 mol) of (S)-asparagine were dissolved in a mixture of 800 ml of water and 500 ml of 2 N sodium hydroxide. Then 500 ml of tetrahydrofuran were added. The mixture was cooled to 0° C., and while keeping the pH at 12.0-12.5 with 2 N sodium hydroxide a solution of 226.7 g (1 mol) of naphthalene-1-sulfonyl chloride in 500 ml of tetrahydrofuran was added within 1 h. The mixture was stirred for 1 h at 0° C. while maintaining the pH at 12.5. Then the mixture was allowed to warm to room temperature, stirred for further 2 h and left at room temperature overnight. The pH was adjusted to about 7 with concentrated hydrochloric acid and the tetrahydrofuran was removed in vakuum in a rotary evaporator. The remaining aqueous solution was cooled to 0° C. and with stirring acidified to pH 0.8 by addition of concentrated hydrochloric acid. After stirring for 30 min at 0° C. the precipitated product was filtered off, washed with water and dried in vacuo at 40° C. Yield: 240 g (75%).
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