CH-Acidity of Amino-acid Esters co-ordinated to Cobalt(III). Racemization during the Formation of Peptides

Article abstract of DOI:10.1039/DT9810002484

Several dipeptide complexes of general formula 3 have been obtained by coupling a chelated ester complex with a free amino-acid ester.The rate of the reaction appears to be quite sensitive to steric hindrance.With chiral amino-acids, the product is a mixture of diastereomers; this result is consistent with a fast racemization coupled with a slight asymmetric induction.The half-life for proton exchange in the complex 3 under the conditions of peptide synthesis is 20 s.The hydrolysis of this ester in methanol (1mol dm^-3 in H2O) is nevertheless faster than racemization.