Novel Modifications of Peptides: Simple Syntheses of Difunctionalized Enamines, Enol Ethers, and Thioenol Ethers from Carboxylic Acids via Acylimidazole and Enol Phosphate Intermediates

Article abstract of DOI:10.1021/jo00297a008

The condensation of carboxylic acids 5 (N-protected amino acids or dipeptides) and active methylene compounds to give difunctionalized enols 6 is accomplished by the use of 1,1'-carbonyldiimidazole as an activating reagent.Enamines 7a, enol ethers 7b, and thioenol ethers 7c are obtained directly from the corresponding nucleophiles and the intermediates formed from enols 6 by the action of phenyl phosphorodichloridate.The integrity of peptide chiral centers is maintained during these transformations.