Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Participants

Reaction Conditions

Reaction Steps

ε-N-2ClZ-L-lysyl-L-prolyl-N-tosyl-L-arginyl-benzyl ester-2-thioamide (2 mmol) was dissolved in anhydrous DMF (0.5 ml) at 0° C. under N2 and α-N-Boc-threonine-O-benzyl ether (2 mmol) was added. HOBt (2 mmol) and DCC (2 mmol) were added portion-wise with stirring at 0° C. and the reaction was allowed to continue overnight. The reaction 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 separatory 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 purified by flash chromatography on silica gel employing a 1:1 hexane-ethyl acetate solvent mixture as an eluant to afford α-N-Boc-L-threonyl-O-benzyl ether-ε-N-2ClZ-L-lysyl-L-prolyl-N-tosyl-L-arginyl-benzyl ester-3-thioamide in high yield.

Provenance & Evidence