RETRACTED: Peptide-Based Inhibitors of Plk1 Polo-box Domain Containing Mono-anionic Phosphothreonine Esters and Their Pivaloyloxymethyl Prodrugs

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been retracted at the request of the authors.Our paper reported small peptide inhibitors of the Plk1 polo-box domain (PBD) that were designed to contain monoanionic phosphothreonine esters. Subsequent analysis has revealed that the structures of peptides 2b–2n, 2c∗, 2m∗, and 3; their associated serine to alanine (S/A) variants; and the X-ray cocrystal structure of 2m bound to the Plk1 PBD (PDB accession code 4MLU) are not as presented in the paper. The pThr residues, which were reported as being monoanionic or neutral, are instead dianionic and monoanionic, respectively. Therefore, the interpretation of the data as reflecting the ability of peptides containing a monoanionic phosphothreonine residue to exhibit high PBD-binding affinity and enhanced cellular efficacy as well as the role of pivaloyloxymethyl (POM) prodrug protection in the observed biological effects are not valid in light of the incorrect structural assignments. As a result, the authors retract the paper.