Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.
J Pept Sci. 2013 Feb;19(2):65-73. doi: 10.1002/psc.2469. Epub 2013 Jan 7.
Native chemical ligation is widely used for the convergent synthesis of proteins. The peptide thioesters required for this process can be challenging to produce, particularly when using Fmoc-based solid-phase peptide synthesis. We have previously reported a route to peptide thioesters, following Fmoc solid-phase peptide synthesis, via an N→S acyl shift that is initiated by the presence of a C-terminal cysteine residue, under mildly acidic conditions. Under typical reaction conditions, we occasionally observed significant thioester hydrolysis as a consequence of long reaction times (~48 h) and sought to accelerate the reaction. Here, we present a faster route to peptide thioesters, by replacing the C-terminal cysteine residue with selenocysteine and initiating thioester formation via an N→Se acyl shift. This modification allows thioester formation to take place at lower temperatures and on shorter time scales. We also demonstrate how application of this strategy also accelerates peptide cyclization, when a linear precursor is furnished with an N-terminal cysteine and C-terminal selenocysteine.
天然化学连接广泛用于蛋白质的汇聚合成。该过程所需的肽硫酯特别难以生产，特别是在使用基于 Fmoc 的固相肽合成时。我们之前报道了一种通过 N→S 酰基转移反应从 Fmoc 固相肽合成后生成肽硫酯的途径，该反应在温和的酸性条件下，由末端半胱氨酸残基引发。在典型的反应条件下，我们偶尔会观察到由于反应时间长（约 48 小时）而导致的显着硫酯水解，并试图加速反应。在这里，我们通过用硒代半胱氨酸代替末端半胱氨酸，并通过 N→Se 酰基转移反应引发硫酯形成，提出了一种更快的生成肽硫酯的方法。该修饰允许在较低温度和较短时间尺度下形成硫酯。我们还展示了如何在提供 N 末端半胱氨酸和 C 末端硒代半胱氨酸的线性前体的情况下，通过应用此策略来加速肽环化。
