Stereoselective synthesis and mechanistic studies of boron-containing antibacterials and beta-lactamase inhibitors

β-内酰胺酶是降解β-内酰胺抗生素的细菌酶，β-内酰胺抗生素是世界上最广泛使用的抗生素。它们的临床疗效受到丝氨酸-β-内酰胺酶（SBL; A、C和D类）和金属-β-内酰胺酶（MBL; B类）的威胁，这两类酶是用于β-内酰胺抗生素水解灭活的两种机制不同的细菌酶。虽然目前有几种市售的SBL抑制剂，但临床上有用的MBL抑制剂尚未开发。该项目旨在通过发现和开发新型含硼小分子来延长β-内酰胺抗生素的临床应用，这些小分子可抑制β-内酰胺酶，从而限制β-内酰胺的降解。近年来，硼类化合物因其独特的理化性质而成为最有前途的广谱β-内酰胺酶抑制剂之一，并引起了科学界的广泛关注。这个项目通过合成各种各样的（a）环状硼酸酯来探索硼的多功能化学，这些硼酸酯的灵感来自天然产物，并来自计算分析。项目目标：优化针对现有硼酸盐支架（例如VNRX-5133）的不对称合成路线，并开发针对新型含硼且水解稳定的MBL、SBL和PBP抑制剂的新的稳健路线; ii.理解和研究不同的双环尺寸（6-5、6-6或更大）、杂化状态（sp2或sp3）和环状硼酸酯的结构构型（闭合或开放）对SBL、MBL和PBPs的抑制的影响; iii.调查为什么环状硼酸酯不能有效地抑制PBP;四、进行力学研究的动态中心，并与这种平衡酶结合/抑制。结果概述：双环硼酸酯VNRX-5133（他尼硼巴坦）和其它（a）环硼酸酯的不对称合成。经过广泛的方法开发/优化工作，VNRX- 5133的优化立体选择性合成已成功完成。人们也在努力开发其他新的双环硼酸酯类似物，有些仍在开发中。这项工作的结果迄今已发表在几个同行评审的出版物上。硼酸盐结合/构象的NMR研究。通过晶体学，观察到VNRX-5133的意外三环抑制剂形式。1H/11B NMR研究正在进行中，以尝试验证这种形式在溶液中的相关性，以及研究这种和其他相关硼酸盐的pH依赖性构象，以尝试深入了解这类化合物在溶液中（在不同pH值下）以及与生物靶标结合时的行为。基于碎片的硼工作：已经合成了双环硼酸酯（6-5/6-6环体系）的文库，并测试了其对一组SBL和MBL的抑制。通过合作研究工作，已经获得了这些具有各种β-内酰胺酶的片段的几种晶体结构。此外，基于片段的药物设计（FBDD）方法用于已合成的几种含硼小分子的计算机设计，一旦系列完成，将对其进行验证。酶对结核病的作用机制研究。细菌细胞壁组分的立体选择性合成正在进行中，其具有用于开发酶测定的潜力。该项目福尔斯以下EPSRC研究领域：研究基础设施（合成有机化学）和医疗保健技术（化学生物学和生物化学）。

Beta-Lactamases are bacterial enzymes that degrade Beta-lactam antibiotics, the most widely prescribed class of antibiotics worldwide. Their clinical efficacy is threatened by serine-Beta-lactamases (SBLs; Classes A, C and D) and metallo-Beta-lactamases (MBLs; Class B), two mechanistically divergent groups of bacterial enzymes used for hydrolytic inactivation of Beta-lactam antibiotics. While there are currently several marketed SBL inhibitors, a clinically useful MBL inhibitor is yet to be developed. This project aims to prolong the clinical utility of Beta-lactam antibiotics through the discovery and development of novel boron-containing small molecules that inhibit Beta-lactamases, thereby limiting the degradation of Beta-lactams. Recently, boron-based molecules have attracted a great deal of scientific attention and are one of the most promising and exciting classes of broad-spectrum Beta-lactamase inhibitors due to the unique and attractive physiochemical properties of boron. This project explores the versatile chemistry of boron through the synthesis of diverse (a)cyclic boronates inspired by natural products and derived from computational analyses. Project Aims: i. To optimise asymmetric synthetic routes towards existing boronate scaffolds (e.g. VNRX-5133) and to develop new robust routes towards novel boron-containing and hydrolytically stable MBL, SBL and PBP inhibitors; ii. To understand and study the effects of varied bicyclic ring sizes (6-5, 6-6 or larger), hybridization states (sp2 or sp3) and structural configurations (closed or open) of cyclic boronates on the inhibition of SBLs, MBLs and PBPs; iii. To investigate why cyclic boronates are not able to effectively inhibit PBPs; iv.To carry out mechanistic studies on the dynamic centre and relate this equilibrium to enzyme binding/inhibition. Results Summary: Asymmetric synthesis of bicyclic boronate VNRX-5133 (Taniborbactam) and other (a)cyclic boronates. Optimised stereoselective synthesis of VNRX- 5133 has been successfully completed, following extensive method development/optimisation efforts. Strenuous efforts towards other novel bicyclic boronate analogues have also been made, some are still in progress. Results from this work have been thus far published in several peer-reviewed publications. NMR investigations of boronate binding/conformation. By crystallography, unexpected tricyclic inhibitor form of VNRX-5133 was observed. 1H/11B NMR studies are in-progress to try verify the relevance of this form in solution, as well to study the pH-dependent conformations of this and other related boronates, in order to try to develop an in-depth understanding of how this class of compounds behaves both in solution (at different pHs) and when engaged with a biological target. Fragment-based boron work: a library of bicyclic boronates (6-5/6-6 ring systems) has been synthesised and tested for inhibition against a panel of SBLs and MBLs. Several crystal structure of these fragments with various beta-lactamases have been obtained through collaborative research efforts. Additionally, a fragment-based drug design (FBDD) approach was used for in silico design of several boron-containing small molecules have been synthesised, and these will be validated once series is completed. Mechanistic studies on enzymes for TB. Stereoselective synthesis of bacterial cell-wall component is in-progress, which has the potential to be used in developed enzyme assays. This project falls within the following EPSRC research areas: Research infrastructure (Synthetic Organic Chemistry) and Healthcare Technologies (Chemical Biology and Biological Chemistry).