New Reactions for Direct, Native Peptide Ligations

描述(申请人提供)：目的：本研究的目标是开发一种通过一种新的化学选择性酰胺化反应直接偶联无保护分子的综合方法。该项目的基础是α-酮酸和N-烷基羟胺的无试剂反应，通过脱羧基和脱水得到酰胺。这些研究将为生物分子靶标的合成提供新的方法，包括蛋白质、糖肽和多肽仿制。具体目的：(1)研究酮酸-羟胺(KAMA)连接的底物范围、局限性和机制，探索不同氨基酸对、不同反应条件和不同片段大小下的多肽连接。进一步的努力将把这一过程应用于合成大肽的新方法。(2)发展新的化学方法，用于实际合成含有必需官能团的片段，即C-端α-酮酸和N-端羟胺。酮酸是通过温和的基于新的固相连接物的两步法制备的。对于羟胺的合成，将确定易于引入合成肽或碳水化合物的单体制备的实用方法。(3)开发了一种不需要偶联剂或保护基的迭代合成多β多肽的新方法。这一独特的多肽合成方法将通过合成适合于合成新的多肽类药物的新单体来扩展。合适的固体载体的设计将使这一过程能够直接应用于具有生物学意义的较长的聚β-肽。意义重大。这项研究将为在生理相容的反应条件下直接合成酰胺提供新的化学工具。它将对复杂生物分子的合成产生重大影响，包括蛋白质、糖蛋白、多肽模拟物和生物相容材料。

DESCRIPTION (provided by applicant): Objective: The goal of the proposed research is to develop a comprehensive method for the direct coupling of unprotected molecules via a new chemoselective amidation reaction. The basis for this project is the reagent-less reaction of alpha-ketoacids and N-alkylhydroxylamines to give amides via decarboxylation and dehydration. These studies will provide new methods for the synthesis of biomolecule targets including proteins, glycopeptides, and peptidomimetics. Specific Aims: (1) To investigate the substrate scope, limitations, and mechanism of the ketoacid-hydroxylamine (KAMA) ligation and explore peptide ligations at various amino acid pairs, reaction conditions, and fragment sizes. Further efforts will apply this process to new approaches for the synthesis of large peptides. (2) To advance new chemistries for the practical synthesis of fragments containing the requisite functional groups, namely C-terminal alpha-ketoacids and N-terminal hydroxylamines. The ketoacids are prepared by a mild two step protocol based on a new solid phase linker. For the synthesis of hydroxylamines, practical approaches to the preparation of monomers that can be easily introduced into a synthetic peptide or carbohydrate will be identified. (3) To develop a new approach to the iterative synthesis of poly-beta-peptides without coupling reagents or protecting groups. This unique approach to polypeptide synthesis will be expanded by synthesizing new monomers suitable for the synthesis of new peptidomimetics. The design of a suitable solid support will enable direct application of this process to longer poly-beta-peptides of biological significance. Significance. The proposed research will provide a new chemical tool for the direct synthesis of amides under physiologically compatible reaction conditions. It will significantly impact the synthesis of complex biomolecules including proteins, glycoproteins, peptidomimetics, and biocompatible materials.