Novel Approaches to the Total Chemical Synthesis of Lasso Peptides as a Scaffold

描述(申请人提供)：在这项探索性拨款中，我们将系统地开发第一个具有天然结构的套索多肽的全化学合成。套索肽是核糖体合成的细菌天然产物，具有广泛的生物活性，如抗微生物或抗病毒药物，以及有效的受体拮抗剂。套索肽 从自然界中分离出来的化合物含有约20个氨基酸，并具有独特的折叠结构，这对它们的稳定性和充分的生物活性是必不可少的。这种折叠结构在N-端氨基酸和谷氨酸或天冬氨酸残基的侧链羧基之间有一个大内酰胺环；C-端线性多肽片段穿过这个环。套索多肽的全化学合成的挑战是形成这种线状结构。尽管套索肽的生物合成已被人们熟知，并可用于设计新的序列，但到目前为止，还没有成功的天然折叠结构的套索肽的全化学合成。在这里，我们描述了合成套索多肽的新方法。合成战略借鉴了本实验室广泛的尖端合成和分析方法，并按合成复杂性增加的顺序排列优先顺序，以便在遇到合成障碍时提供多种替代方案的实施。建议的路线是本实验室开发的硫酯介导的、形成酰胺的天然化学连接方法的新扩展，与我们在肽合成方法方面的广泛专业知识相结合。我们合成产品的折叠结构将通过已建立的核磁共振和质谱学方法以及本实验室最近开创的用于确定未知X射线结构的外消旋蛋白质结晶学方法来明确确定。所有合成产品都将经过筛选，以防止一组致病细菌。套索多肽的成功全化学合成将使我们能够系统地剖析这类重要的自然产品中的结构-功能关系，并将使套索多肽支架在开发新型抗菌药物方面能够使用更广泛的构建块。

DESCRIPTION (provided by applicant): In this exploratory grant we will systematically develop the first total chemical synthesis of lasso peptides of native structure. Lasso peptides are ribosomally synthesized bacterial natural products that have a broad spectrum of biological activities as antimicrobial or antiviral agents, and as potent receptor antagonists. Lasso peptides isolated from nature have ~20 amino acids and have a unique folded structure that is essential for their stability and for full biological activity. This folded structure has a macrolactam ring between the N-terminal amino acid and the side chain carboxyl of a glutamic acid or aspartic acid residue; the C-terminal linear peptide segment is threaded through this ring. The challenge in total chemical synthesis of lasso peptides is forming this threaded structure. Although the biosynthesis of lasso peptides is quite well understood and can be used to engineer novel sequences, to date there has been no successful total chemical synthesis of a lasso peptide of native folded structure. Here we describe novel approaches to the synthesis of lasso peptides. The synthetic strategies draw on the broad range of cutting edge synthetic and analytical methods in this laboratory, and are prioritized in order of increasing synthetic complexity to provide for versatile implementation of alternatives if/when synthetic obstacles are encountered. The proposed routes are novel extensions of the thioester-mediated, amide-forming native chemical ligation methods developed in this laboratory, used in combination with our extensive expertise in peptide synthetic methods. The folded structures of our synthetic products will be unambiguously determined by established NMR and mass spectrometric methods, and by the racemic protein crystallography method recently pioneered in this laboratory for the determination of unknown Xray structures. All synthetic products will be screened against a panel of pathogenic bacteria. Successful total chemical synthesis of lasso peptides will enable the systematic dissection of the structure-function relationships in this important class of natura products and will enable the use of a much wider range of building blocks for the exploitation of the lasso peptide scaffold in the development of novel antibacterials.