Peptidyl 3-substituted 1-hydroxyureas as isosteric analogues of succinylhydroxamate MMP inhibitors

To evaluate N-hydroxyurea as zinc binding group in the design of MMP inhibitors, two peptidyl 1-hydroxyureas were prepared by N-hydroxycarbamoylation of the diastereomeric dipeptides H-Leu-Phe-NHMe and H-d-Leu-Phe-NHMe. Peptidyl 1-hydroxyureas were more potent than the parent peptides, but dramatically weaker (4–5 orders of magnitude) than the isosteric (R)-succinylhydroxamate analogue, which displays IC50 in the range of nM vs MMP-1, -3, -7 and sub-nM vs MMP-2, -8, and -9. The peptidyl 1-hydroxyurea 1a attained an IC50 of 20 μM vs MMP-9, and substantially approaches inhibition of known N-hydroxyureas based on aminoacids or peptides against other zinc metalloenzymes and non-peptidic N-hydroxyureas against MMPs. Strong preference of the O–N1–CO unit for the antiperiplanar amide bond conformation seems to be the major limit for more effective zinc chelation. Methylation of a peptidyl 1-hydroxyurea at N3, to promote the synperiplanar O–N1–CO conformation required for zinc chelation and improve affinity, resulted in release of a methylimidazolidine-2,4-dione through an undesired intramolecular reaction reminiscent of the Edman peptide degradation.

Peptidyl-1-hydroxyureas are easily prepared by N-hydroxycarbamoylation of suitable dipeptides. Their potency against six MMPs approaches that of other N-hydroxyurea ligands against various zinc metalloenzymes, but is at least 50,000-fold lower than that of their succinylhydroxamate analogues.Figure optionsDownload as PowerPoint slide