Suppression of Formation of N,N′-Dicyclohexylurea Derivatives During DCC-Activation of Proline-Containing Dipeptides
作者:Gregor Radau
DOI:10.1007/s00706-003-0007-3
日期:2003.6
The syntheses of dipeptide esters containing a C-terminal L-proline moiety using carbodiimides as coupling reagents strongly depend on the choice of appropriate conditions. Thus, the use of DCC prefers the formation of the undesirable N,N'-dicyclohexylurea derivative 3 as a consequence of a CO --> N-shift in the O-acyl isourea intermediate instead of the desired dipeptide ester 4. In our hands, only DIC was able to yield the desired product exclusively.