Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Participants

Reaction Steps

Fmoc-D-Glu-OH (59.8 g, 1.0 eq) was dissolved in anhydrous tetrahydrofuran (THF) (324 mL). DCC (40.1 g, 1.2 eq) was then added while stirring in ice-water bath. The reaction mixture was allowed to warm to r.t and stirring was maintained for additional 8 h to produce 1,3-dicyclohexylurea (DCU). The precipitates were filtered off, and washed with small amount THF. Dry ammonia gas was then bubbled through the filtrate which was stirred in a NaCl salt-ice bath. The reaction was completed after 1.5 h when no more white solid was precipitated. Still standing for 30 min, small amount MeOH was added to dissolve the solid. The mixture was cooled in an ice-water bath again. Then 2.0 N HCl was added carefully and slowly to adjust pH to 2-3. The solvent was evaporated under vacuum. The resulting solid was dissolved in AcOEt and then washed with diluted HCl, saturated aqueous NaHCO3 solution, and H2O sequentially. The organic layer was separated and combined, then dried with MgSO4 overnight, filtered and evaporated under vacuum. Then residue was recrystallized with ethylacetate-cyclohexane system. After filtration, 46.5 g target product was obtained with a yield of 78%. m.p.=204˜205° C., [α]=−4.2° (C=10 mg/mL, DMF).

Provenance & Evidence