Dimedone (5,5-Dimethylcyclohexane-1,3-dione) as a protecting agent for amino groups in peptide synthesis

The reaction of dimedone (5,5-dimethylcyclohexane-1,3-dione) with amino-acid "active" esters leads to optically pure enamine derivatives. The dimedone derivatives of amino acid esters could also be converted by way of their hydrazides to the corresponding azides. The thiophenyl ester and azide derivatives have been used directly for peptide synthesis. The protecting group can easily be removed from the N-protected peptides by means of aqueous bromine, with the formation of 2,2-dibromodimedone and the hydrobromide of the corresponding peptide ester.