In response to the extensive use of antibiotics, bacteria have evolved numerous mechanisms of defense against antimicrobial agents. Among them, extrusion of the antimicrobial agents outside the bacterial cell through efflux pumps is a major cause of concern. At first limited to one or few structurally-related antibiotics, bacterial resistance have then progressed towards cross-resistance between different classes of antibiotics, leading to multidrug-resistant microorganisms. Emergence of these pathogens requires development of novel therapeutic strategies and inhibition of efflux pumps appears to be a promising strategy that could restore the potency of existing antibiotics. NorA is the most studied chromosomal efflux pump of Staphylococcus aureus; it is known to be implied in resistance of Methicillin-resistant S. aureus (MRSA) strains against a wide range of unrelated substrates, including hydrophilic fluoroquinolones. Starting from 6-benzyloxypyridine-3-boronic acid I that we previously identified as a potential inhibitor of the NorA efflux pump against the NorA-overexpressing S. aureus 1199B strain (SA1199B), we describe here the synthesis and biological evaluation of a series of 6-(aryl)alkoxypyridine-3-boronic acids. 6-(3-Phenylpropoxy)pyridine-3-boronic acid 3i and 6-(4-phenylbutoxy)pyridine-3-boronic acid 3j were found to potentiate ciprofloxacin activity by a 4-fold increase compared to the parent compound I. In addition, it has been shown that both compounds promote Ethidium Bromide (EtBr) accumulation in SA1199B, thus corroborating their potential mode of action as NorA inhibitors.

响应于抗生素的广泛使用，细菌已经进化出许多防御抗菌剂的机制。其中，通过外排泵将抗菌剂挤出细菌细胞外是引起关注的主要原因。起初仅限于一种或几种与结构相关的抗生素，然后细菌耐药性逐渐发展为不同种类抗生素之间的交叉耐药性，从而产生了多药耐药性微生物。这些病原体的出现需要开发新的治疗策略，抑制外排泵似乎是可以恢复现有抗生素效力的有前途的策略。NorA是金黄色葡萄球菌研究最多的染色体外排泵; 已知这暗示了耐甲氧西林的金黄色葡萄球菌（MRSA）菌株对包括亲水性氟喹诺酮在内的各种无关底物的抗性。从我们先前鉴定为NorA过表达Sure aureus金黄色葡萄球菌1199B菌株（SA1199B）的NorA外排泵的潜在抑制剂的6-苄氧基吡啶-3-硼酸I开​​始，我们在此描述一系列6-（芳基）烷氧基吡啶-3-硼酸。发现6-（3-苯丙氧基）吡啶-3-硼酸3i和6-（4-苯基丁氧基）吡啶-3-硼酸3j与母体化合物I相比，环丙沙星活性增强了4倍。。此外，已显示这两种化合物均能促进SA1199B中的溴化乙锭（EtBr）积累，从而证实了它们作为NorA抑制剂的潜在作用方式。