Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Participants

Reaction Steps

One equivalent (2.24 g, 0.01 mole) of HNSA was mixed together - with one equivalent (2.06 g, 0.01 mole) of dicyclohexylcarbodiimide and one equivalent (2.10 g, 0.01 mole) of N-maleimido-6-aminocaproic acid in 25 ml of DMF at room temperature overnight. A white precipitate of dicyclohexyl urea was formed. The precipitate was filtered and 300 ml diethyl ether was added to the mother liquor. After about 10 minutes to four hours a gummy solid that precipitated from the mother liquor was formed. This solid was found to contain 58% of active HNSA ester and 42% of free HNSA by the analysis described above. The product was positively identified as mal-sac-HNSA ester by its reactivity with amines. The yield of the pure ester was estimated to be approximately 30% of theoretical; the purified material consisted of 99% ester.

Provenance & Evidence