Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Participants

Reaction Steps

Folic Acid (Sigma Chemical Co., St. Louis, MO. 1 g, 2.1 mmol) was dissolved in 10 ml of dimethyl sulfoxide (Fluka) pre-dried with a molecular sieve. To this solution, N-hydroxysuccinimide (NHS) (Pierce, 0.242 g., 2 mmol) or N-hydroxybenzotriazole (Fluka, 0.270 g., 2 mmol) was added. At this point 1,3-dicyclohexylcarbodiimide (Fluka, 0.872 g., 4 mmol) dissolved in a small volume of dimethyl sulfoxide was then slowly added to this solution. The reaction was allowed to proceed overnight in the dark at room temperature under stirring. Dicyclohexylurea formed as a white precipitate was removed by filtering twice the reaction mixture through 40 mesh filter paper. The DMSO was then removed by distillation under vacuum at 45° C. until the solution became viscous gel. The product (NHS-folate or benzotriazole-folate) was then crystallized in an excess volume of anhydrous ether. A small amount of methanol was added to accelerate the crystallization process. A fine yellow powder of NHS-folate or benzotriazole-folate formed at this point was subsequently washed twice with anhydrous ether. The product was then dried under vacuum and stored at 4° C.

Provenance & Evidence