Boronic acid transition state inhibitors (BATSIs) are known reversible covalent inhibitors of serine β-lactamases. The selectivity and high potency of specific BATSIs bearing an amide side chain mimicking the β-lactam’s amide side chain are an established and recognized synthetic strategy. Herein, we describe a new class of BATSIs where the amide group is replaced by a bioisostere triazole; these compounds were designed as molecular probes. To this end, a library of 26 α-triazolylmethaneboronic acids was synthesized and tested against the clinically concerning Acinetobacter -derived cephalosporinase, ADC-7. In steady state analyses, these compounds demonstrated K i values ranging from 90 nM to 38 μM (±10%). Five compounds were crystallized in complex with ADC-7 β-lactamase, and all the crystal structures reveal the triazole is in the putative amide binding site, thus confirming the triazole–amide bioisosterism. The easy synthetic access of these new inhibitors as prototype scaffolds allows the insertion of a wide range of chemical groups able to explore the enzyme binding site and provides insights on the importance of specific residues in recognition and catalysis. The best inhibitor identified, compound 6q ( K i 90 nM), places a tolyl group near Arg340, making favorable cation−π interactions. Notably, the structure of 6q does not resemble the natural substrate of the β-lactamase yet displays a pronounced inhibition activity, in addition to lowering the minimum inhibitory concentration (MIC) of ceftazidime against three bacterial strains expressing class C β-lactamases. In summary, these observations validate the α-triazolylboronic acids as a promising template for further inhibitor design.

Design of novel β-lactamase inhibitors (BLIs) is one of the currently accepted strategies to combat the threat of cephalosporin and carbapenem resistance in Gram-negative bacteria. B oronic a cid t ransition s tate i nhibitors (BATSIs) are competitive, reversible BLIs that offer promise as novel therapeutic agents. In this study, the activities of two α-amido-β-triazolylethaneboronic acid transition state inhibitors (S02030 and MB_076) targeting representative KPC (KPC-2) and CTX-M (CTX-M-96, a CTX-M-15-type extended-spectrum β-lactamase [ESBL]) β-lactamases were evaluated.

Acinetobacter baumannii is a Gram-negative organism listed as an urgent threat pathogen by the World Health Organization (WHO). Carbapenem-resistant A. baumannii (CRAB), especially, present therapeutic challenges due to complex mechanisms of resistance to β-lactams. One of the most important mechanisms is the production of β-lactamase enzymes capable of hydrolyzing β-lactam antibiotics. Co-expression of multiple classes of β-lactamases is present in CRAB; therefore, the design and synthesis of “cross-class” inhibitors is an important strategy to preserve the efficacy of currently available antibiotics. To identify new, nonclassical β-lactamase inhibitors, we previously identified a sulfonamidomethaneboronic acid CR167 active against Acinetobacter-derived class C β-lactamases (ADC-7). The compound demonstrated affinity for ADC-7 with a Ki = 160 nM and proved to be able to decrease MIC values of ceftazidime and cefotaxime in different bacterial strains. Herein, we describe the activity of CR167 against other β-lactamases in A. baumannii: the cefepime-hydrolysing class C extended-spectrum β-lactamase (ESAC) ADC-33 and the carbapenem-hydrolyzing OXA-24/40 (class D). These investigations demonstrate CR167 as a valuable cross-class (C and D) inhibitor, and the paper describes our attempts to further improve its activity. Five chiral analogues of CR167 were rationally designed and synthesized. The structures of OXA-24/40 and ADC-33 in complex with CR167 and select chiral analogues were obtained. The structure activity relationships (SARs) are highlighted, offering insights into the main determinants for cross-class C/D inhibitors and impetus for novel drug design.

A straightforward concise synthesis of chiral non-racemic aliphatic α-boryl isocyanides, relay intermediates for boron-based bioactive molecules by using multicomponent reaction, is presented. The short synthetic sequence comprises as key steps...

Boronic acids are known reversible covalent inhibitors of serine β‐lactamases. The selectivity and high potency of specific boronates bearing an amide side chain that mimics the β‐lactam's amide side chain have been advanced in several studies. Herein, we describe a new class of boronic acids in which the amide group is replaced by a bioisostere triazole. The boronic acids were obtained in a two‐step synthesis that relies on the solid and versatile copper‐catalyzed azide–alkyne cycloaddition (CuAAC) followed by boronate deprotection. All of the compounds show very good inhibition of the Klebsiella pneumoniae carbapenemase KPC‐2, with Ki values ranging from 1 nM to 1 μM, and most of them are able to restore cefepime activity against K. pneumoniae harboring blaKPC‐2. In particular, compound 1 e, bearing a sulfonamide substituted by a thiophene ring, proved to be an excellent KPC‐2 inhibitor (Ki=30 nM); it restored cefepime susceptibility in KPC‐Kpn cells (MIC=0.5 μg/mL) with values similar to that of vaborbactam (Ki=20 nM, MIC in KPC‐Kpn 0.5 μg/mL). Our findings suggest that α‐triazolylboronates might represent an effective scaffold for the treatment of KPC‐mediated infections.