A synthetic approach to a peptide α-thioester from an unprotected peptide through cleavage and activation of a specific peptide bond by N-acetylguanidine.
A synthetic approach to a peptide α-thioester from an unprotected peptide through cleavage and activation of a specific peptide bond by N-acetylguanidine.
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DOI：
10.1002/anie.201105601
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发表时间：
2012-01
影响因子：
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通讯作者：
Ryosuke Okamoto;Keiko Morooka;Y. Kajihara
中科院分区：
文献类型：
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作者：
Ryosuke Okamoto;Keiko Morooka;Y. Kajihara
在全化学蛋白质合成的现代过程中，化学连接的概念在靶蛋白多肽链的组装中起着至关重要的作用。[1]肽α-硫酯是化学连接如天然化学连接（NCL）、直接片段偶联方法或无痕施陶丁格连接的关键组分。[2]因此，在建立基于常规Boc或Fmoc固相肽合成（SPPS，Boc=叔丁氧羰基，Fmoc= 9-芴基甲氧羰基）的肽-α硫酯合成方面已经花费了大量的努力。[3]然而，由于SPPS的固有局限性，合成具有超过50个氨基酸（aa）的肽α硫酯仍然具有挑战性。为了制备这种多肽α硫酯，使用内含肽系统的表达方法已被认为是一种能够提供超过50个aa的多肽α-硫酯的稳健技术。[4]受生物系统的启发，我们探索了一种类似内含肽的化学方法，以天然（未保护的）肽为起始原料制备长肽α硫酯。最近有人报道了E.大肠杆菌表达的肽使用酸处理，但这些有趣的方法导致C-末端氨基酸残基的差向异构化，并且仍然具有序列限制。[5]因此，我们开始寻找一种广泛适用的新方法，其关键点是操纵一个未保护的肽来安装一个C-末端α-硫酯。这项任务似乎需要选择性活化天然酰胺键和随后的硫解。最近，几个研究小组报道了激活肽骨架以在肽C末端安装α-硫酯的巧妙方法。[6]在这些方法中，通过在特定氨基酸残基上的Nα-酰胺氮原子的选择性酰化策略来进行肽键的活化。为了研究未保护肽的硫代酯化，我们专注于半胱氨酸（Cys）残基，因为Cys具有巯基，其可能比其他氨基酸侧链更容易修饰，从而选择性地诱导N-酰化。事实上，在Cys残基处使用N-甲基-N-异丙基-N-甲基-N-
In modern procedures for total chemical protein synthesis, the concept of chemical ligation plays an essential role in the assembly of target protein polypeptide chains.[1] The peptide α-thioester is the key component for chemical ligation such as native chemical ligation (NCL), direct segment coupling methods, or traceless Staudinger ligation.[2] Thus, substantial effort has been expended on the establishment of peptide-αthioester synthesis based on conventional Boc or Fmoc solidphase peptide synthesis (SPPS, Boc= tert-butoxycarbonyl, Fmoc= 9-fluorenylmethyloxycarbonyl).[3] However, because of the inherent limitations of SPPS, synthesis of peptide αthioesters with more than 50 amino acids (aa) is still challenging. For the preparation of such a polypeptide αthioester, an expression method using the intein system has come to be recognized as a robust technology with the capacity to provide polypeptide α-thioesters of more than 50 aa.[4] Inspired by the biological system, we explored an inteinlike chemical methodology for preparing a long peptide αthioester by using a native (unprotected) peptide as the starting material. Some groups recently reported thioesterification of E. coli-expressed peptides using acid treatment, but these intriguing methods lead to epimerization of the C-terminal amino acid residue and still have sequence limitations.[5] Thus we set out to find a widely usable new methodology.The key point was the manipulation of an unprotected peptide to install a C-terminal α-thioester. This task appears to require the selective activation of a native amide bond and subsequent thiolysis. Recently, several groups reported elegant methods of activating the peptide backbone to install an α-thioester at the peptide C terminus.[6] In these methods, the activation of the peptide bond was performed by a selective acylation strategy of an Nα-amide nitrogen atom at a specific amino acid residue. To examine the thioesterification of unprotected peptides, we focused on the cysteine (Cys) residue, because Cys possesses a thiol group, which might be more easily modified than the other amino acid side chains and thus selectively induce N-acylation. In fact, selective peptide-cleavage methods at the Cys residue employing an N-