Activation peptides guanidination

Most solid-phase strategies for the preparation and protection of guanidines were developed to enable the use of arginine in solid-phase peptide synthesis. In recent years, however, the biological activity of many guanidines has spurred a quest for more versatile solid-phase syntheses of this class of compound. 

The introduction of carbodiimides (Sheehan and Hess 1955), particularly dicy-clohexylcarbodiimide (DCC, DCCI) as reagents for the formation of the peptide bond was a major event in the history of peptide synthesis. The novel feature of coupling reagents was that they could be added to the mixture of the carboxyl component and the amine component. Thus, activation and coupling proceed concurrently. While amines do react with carbodiimides (yielding guanidine derivatives) the rate of this reaction is negligible when compared with the rapid rate observed in the addition of carboxylic acids to one of the double bonds of a carbodiimide ... 

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