Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Participants

Reaction Steps

ε-N-2ClZ-L-lysyl-L-aspartyl-β-benzyl ester-L-valyl-L-tyrosyl-O-benzyl ether-benzyl ester-3-thioamide (2 mmol) was dissolved in dry DMF (0.5 ml) at 0° C. under N2 and α-N-Boc-N-tosyl-L-arginine (2 mmol) was added to the solution with stirring. HOBt (2 mmol) and DCC (2 mmol) were added slowly at 0° C. and stirring was allowed to continue overnight. The mixture was diluted with 8 volumes of ethyl acetate and the N,N'-dicyclohexylurea so formed was filtered away from the solution. The filtrate was transferred to a separating funnel and washed successively with 5% aqueous sodium bicarbonate, 5% aqueous citric acid, and saturated brine. The organic phase was collected and dried over MgSO4, filtered, and concentrated in vacuo. The residue was purification by flash chromotography using 9:1 chloroform-methanol as an eluant to afford the α-N-Boc-N-tosyl-L-arginyl-ε-N-2ClZ-L-lysyl-L-aspartyl-β-benzyl ester-L-valyl-L-tyrosyl-O-benzyl ether-benzyl ester-4-thioamide in good yield (78%). The following physical characteristics were recorded for the compound: Melting point 105°-107° C.; IR (CHCl3) 1756, 1%90 cm-1UV (CHCl3) lambdamax 271. Elemental composition (C71H84Cl3N9O14S2): Theoretical: C, 58.13; H, 5.65; N, 8.34; S, 4.79. Found: C, 58.54; H, 5.81; N, 8.65; S, 4.40.

Provenance & Evidence