New Reactions for Direct, Native Peptide Ligations

描述（由申请人提供）：目的：拟议研究的目标是开发一种通过新的化学选择性酰胺化反应直接偶联未保护分子的综合方法。该项目的基础是α-酮酸和N-烷基羟胺通过脱羧和脱水反应生成酰胺的无试剂反应。这些研究将为蛋白质、糖肽和肽模拟物等生物分子靶标的合成提供新的方法。具体目标：（1）研究酮酸-羟胺（KAMA）连接的底物范围、限制和机制，并探索不同氨基酸对、反应条件和片段大小的肽连接。进一步的努力将把这一过程应用于合成大肽的新方法。(2)推进新的化学方法，用于实际合成含有必要官能团（即C-末端α-酮酸和N-末端羟胺）的片段。基于新的固相连接剂，通过温和的两步方案制备酮酸。对于羟胺的合成，将确定制备可以容易地引入合成肽或碳水化合物的单体的实用方法。(3)开发一种无需偶联试剂或保护基的多聚β肽迭代合成新方法。这种独特的多肽合成方法将通过合成适合于合成新的肽模拟物的新单体来扩展。合适的固体支持物的设计将使该过程能够直接应用于具有生物学意义的更长的聚β肽。意义该研究为在生理相容的反应条件下直接合成酰胺提供了一种新的化学工具。它将显著影响复杂生物分子的合成，包括蛋白质、糖蛋白、肽模拟物和生物相容性材料。

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.