N,N -Dicyclohexylcarbodiimide (DCC) is a dehydrating agent often used to form esters, amides or anhydrides. It is commercially available as a waxy low-melting solid (34-35°C). It can also be prepared by oxidation of dicyclohexylurea with p -toluenesulfonyl chloride in hot pyridine or by heating dicyclohexylthiourea with yellow mercuric oxide (Scheme 1). The section covers some important applications in organic synthesis.

Scheme 1

 

J.S. Albert, A. D. Hamilton, Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette, Ed., New York, 1995, 3 , 1751.

5.2.1 Synthesis of Peptides

DCC is useful for the coupling of amino acids via amide C-N bonds. The amino acid monomers should be such that the ends to be available and other reactive groups protected. For example, for the synthesis of dipeptide between to two α -amino acids, the amino group of one of the amino acids and the carboxylic group of the other must be protected before the two amino acids are brought together in the presence of DCC (Scheme 2).

Scheme 2

Mechanism

DCC reacts with the carboxyl group of amino protected acid to give activated acylating agent that undergoes reaction with amino group of other amino acid to form of a new amide bond (Scheme 3).

Scheme 3