Dichloromethane → N,N'-Dicyclohexylurea

Participants

Reaction Steps

FMOC-(O-t-Butyl)tyr-val (1.0 gm, 1.8 mMole) and N-hydroxysuccinimide (210 mg, 1.8 mMole) were dissolved in 40 ml THF under nitrogen at 0.C. Dicyclohexylcarbodiimide (DCC) was added as a methylene chloride solution (0.5M, 3.6 ml, 1.8 mMole) and the reaction mixture was incubated for 2 hours with stirring, then stored overnight at 4° C. TLC showed incomplete reaction, so additional DCC was added (0.45 mMole), and the reaction mixture incubated at room temperature for one day. Dicyclohexylurea (DCU) formed was filtered and the filtrate concentrated to a solid, which was triturated with 4% sodium bicarbonate. The solid was filtered, washed with water dried, then crystallized from chloroform/petroleum ether. A white solid was obtained on filtration and air drying. Yield: 761 mg (65%); Rf: 0.75 [chloroform/methanol 9:1 (silica)]. Elemental analysis for C37H41N3O8.0.5H2O calculated: C, 66.85; H, 6.37; observed C, 67.04; H, 6.85.

Provenance & Evidence