N-Benzyl Residues as the P1' Substituents in Phosphorus-Containing Extended Transition State Analog Inhibitors of Metalloaminopeptidases.

Kamila Janiszewska,Paweł Kafarski,Artur Mucha,Bartosz Oszywa,Michał Talma,Małgorzata Pawełczak

doi:10.3390/molecules25184334

Abstract

Peptidyl enzyme inhibitors containing an internal aminomethylphosphinic bond system (P(O)(OH)-CH2-NH) can be termed extended transition state analogs by similarity to the corresponding phosphonamidates (P(O)(OH)-NH). Phosphonamidate pseudopeptides are broadly recognized as competitive mechanism-based inhibitors of metalloenzymes, mainly hydrolases. Their practical use is, however, limited by hydrolytic instability, which is particularly restricting for dipeptide analogs. Extension of phosphonamidates by addition of the methylene group produces a P-C-N system fully resistant in water conditions. In the current work, we present a versatile synthetic approach to such modified dipeptides, based on the three-component phospha-Mannich condensation of phosphinic acids, formaldehyde, and N-benzylglycines. The last-mentioned component allowed for simple and versatile introduction of functionalized P1′ residues located on the tertiary amino group. The products demonstrated moderate inhibitory activity towards porcine and plant metalloaminopeptidases, while selected derivatives appeared very potent with human alanyl aminopeptidase (Ki = 102 nM for 6a). Analysis of ligand-protein complexes obtained by molecular modelling revealed canonical modes of interactions for mono-metallic alanyl aminopeptidases, and distorted modes for di-metallic leucine aminopeptidases (with C-terminal carboxylate, not phosphinate, involved in metal coordination). In general, the method can be dedicated to examine P1′-S1′ complementarity in searching for non-evident structures of specific residues as the key fragments of perspective ligands.

Highlights

Phosphonamidate peptide analogues, compounds that comprise a direct nitrogen-to-phosphorus bond (-P(O)(OH)-NH, P[NH]) introduced instead of an amide bond, have been reported as exceptionally active inhibitors of metalloproteases [1].For example, pseudotripeptideCbz-PheP[NH]Leu-Ala-OH, a competitive thigh-binding inhibitor of thermolysin, which is ranked among the most potent inhibitors of this type, displayed a Ki value in the picomolar range [2].It is commonly believed that such an affinity originates from structural and electronic similarity of phosphonamidates to the gem-diolate intermediate of the amide bond hydrolysis, which is stabilized by favorable interactions in the metalloenzyme active sites [3,4]
Complexation with the metal ion(s) and important contacts provided by the Consistent with these analogies, phosphonamidate peptides are classified as transitiongroup. Consistent with these analogies, phosphonamidate peptides classified as transition state inhibitors
We report the synthesis of pseudodipeptide compounds of the general formula

Summary

Introduction

It is commonly believed that such an affinity originates from structural and electronic similarity of phosphonamidates to the gem-diolate intermediate of the amide bond hydrolysis, which is stabilized by favorable interactions in the metalloenzyme active sites [3,4]. These interactions include, first of Molecules 2020, 25, 4334; doi:10.3390/molecules25184334 www.mdpi.com/journal/molecules. Complexation with the metal ion(s) and important contacts provided by the NH Consistent with these analogies, phosphonamidate peptides are classified as transitiongroup. These interactions include, first of all, specific hydrogen bonds formed by the phosphoryl oxygen atoms with the enzyme resides and all, specific hydrogen phosphoryl with the enzyme complexation with thebonds metalformed ion(s) by butthe important oxygen contactsatoms provided by the NH resides group.

Methods

Discussion

Conclusion