Truncated aminoglycoside-coenzyme A bisubstrate analogues were efficiently prepared using a convergent approach where the amine and the thiol are coupled in one pot with the addition of a linker, without the need for protecting groups. These derivatives were tested for their effect on the activity of the resistance-causing enzyme aminoglycoside 6'-N-acetyltransferase Ii, and key structure-activity relationships are reported. Moreover, one of the inhibitors is able to block aminoglycoside resistance in cells expressing this enzyme.

Einfach zu komplexen nanomolaren Inhibitoren: Aminoglycosid‐Coenzym‐A‐Derivate wurden durch eine effiziente regioselektive 6′‐N‐Modifizierung von Aminoglycosiden hergestellt (siehe Schema). Diese Bisubstrate sind fest bindende kompetitive Inhibitoren der Aminoglycosid‐6′‐N‐Acetyltransferase, eines an der Antibiotikaresistenz beteiligten Enzyms.

Complex nanomolar inhibitors in one pot: Aminoglycoside–coenzyme A derivatives were prepared through an efficient regioselective 6′‐N modification of aminoglycosides (see scheme). These bisubstrates show tight‐binding competitive inhibition of aminoglycoside 6′‐N‐acetyltransferase, an enzyme involved in antibiotic resistance.

The most common mechanism of resistance to aminoglycoside antibiotics entails bacterial expression of drug-metabolizing enzymes, such as the clinically widespread aminoglycoside N-6'-acetyltransferase (AAC(6')). Aminoglycoside-CoA bisubstrates are highly potent AAC(6') inhibitors; however, their inability to penetrate cells precludes in vivo studies. Some truncated bisubstrates are known to cross cell membranes, yet their activities against AAC(6') are in the micromolar range at best. We report here the synthesis and biological activity of aminoglycoside-pantetheine derivatives that, although devoid of AAC(6') inhibitory activity, can potentiate the antibacterial activity of kanamycin A against an aminoglycoside-resistant strain of Enterococcus faecium. Biological studies demonstrate that these molecules are potentially extended to their corresponding full-length bisubstrates by enzymes of the coenzyme A biosynthetic pathway. This work provides a proof-of-concept for the utility of prodrug compounds activated by enzymes of the coenzyme A biosynthetic pathway, to resensitize resistant strains of bacteria to aminoglycoside antibiotics.

Aminoglycoside N-6′-acetyltransferases (AAC(6′)s) are important determinants of antibiotic resistance. A good mechanistic understanding of these enzymes is essential to overcome aminoglycoside resistance. We have previously reported the synthesis of amide-linked and sulfonamide-linked aminoglycoside-coenzyme A conjugates which were useful mechanistic and structural probes of AAC(6′)s. We report here the synthesis of a phosphonate-linked aminoglycoside-coenzyme A variant, which is expected to be a superior mimic of the tetrahedral intermediate proposed for catalysis by AAC(6′)s. This synthetic target is especially challenging for a number of reasons including the presence of multiple functional groups, the water solubility of both starting materials, and incompatibility of P(III) chemistry with water. We have overcome these challenges by adding the expensive coenzyme A in the last step via an elegant Michael-type addition onto a vinylphosphonate in water. Overall, a single protection step was needed. The decreased inhibitory potency of this bisubstrate compared to that of the amide-linked analog suggests that Enterococcus faecium AAC(6′)-Ii may not stabilize the proposed tetrahedral intermediate, and may act mainly via proximity catalysis.