Summary.
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.
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E-mail: radau@pharmazie.uni-greifswald.de
Received November 7, 2002; accepted December 4, 2002 Published online May 6, 2003
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Radau, G. Suppression of Formation of N,N′-Dicyclohexylurea Derivatives During DCC-Activation of Proline-Containing Dipeptides. Monatshefte für Chemie 134, 1033–1036 (2003). https://doi.org/10.1007/s00706-003-0007-3
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DOI: https://doi.org/10.1007/s00706-003-0007-3