There are many examples of bioactive, disulfide‐rich peptides and proteins whose biological activity relies on proper disulfide connectivity. Regioselective disulfide bond formation is a strategy for the synthesis of these bioactive peptides, but many of these methods suffer from a lack of orthogonality between pairs of protected cysteine (Cys) residues, efficiency, and high yields. Here, we show the utilization of 2,2′‐dipyridyl diselenide (PySeSePy) as a chemical tool for the removal of Cys‐protecting groups and regioselective formation of disulfide bonds in peptides. We found that peptides containing either Cys(Mob) or Cys(Acm) groups treated with PySeSePy in trifluoroacetic acid (TFA) (with or without triisopropylsilane (TIS) were converted to Cys‐S–SePy adducts at 37 °C and various incubation times. This novel Cys‐S–SePy adduct is able to be chemoselectively reduced by five‐fold excess ascorbate at pH 4.5, a condition that should spare already installed peptide disulfide bonds from reduction. This chemoselective reduction by ascorbate will undoubtedly find utility in numerous biotechnological applications. We applied our new chemistry to the iodine‐free synthesis of the human intestinal hormone guanylin, which contains two disulfide bonds. While we originally envisioned using ascorbate to chemoselectively reduce one of the formed Cys‐S–SePy adducts to catalyze disulfide bond formation, we found that when pairs of Cys(Acm) residues were treated with PySeSePy in TFA, the second disulfide bond formed spontaneously. Spontaneous formation of the second disulfide is most likely driven by the formation of the thermodynamically favored diselenide (PySeSePy) from the two Cys‐S–SePy adducts. Thus, we have developed a one‐pot method for concomitant deprotection and disulfide bond formation of Cys(Acm) pairs in the presence of an existing disulfide bond.

中文翻译：

---

2,2'-Dipyridyl diselenide：一种用于半胱氨酸脱保护和二硫键形成的化学选择性工具。


有许多富含二硫键的生物活性肽和蛋白质的例子，其生物活性依赖于适当的二硫键连接。区域选择性二硫键形成是合成这些生物活性肽的一种策略，但其中许多方法缺乏受保护的半胱氨酸 (Cys) 残基对之间的正交性、效率和高产率。在这里，我们展示了利用 2,2'-二吡啶基二硒化物 (PySeSePy) 作为化学工具来去除肽中的 Cys 保护基团和区域选择性形成二硫键。我们发现含有 Cys(Mob) 或 Cys(Acm) 基团的肽在三氟乙酸 (TFA)（有或没有三异丙基硅烷 (TIS)）中用 PySeSePy 处理，在 37°C 和不同的孵育时间下转化为 Cys-S-SePy 加合物这种新型的 Cys-S-SePy 加合物能够在 pH 4.5 下被五倍过量的抗坏血酸化学选择性还原，这种条件应该可以避免已经安装的肽二硫键被还原，这种抗坏血酸的化学选择性还原无疑会在许多生物技术中得到应用。我们将新的化学方法应用于人类肠道激素鸟苷酸的无碘合成，鸟苷酸含有两个二硫键，而我们最初设想使用抗坏血酸来化学选择性地还原形成的 Cys-S-SePy 加合物之一以催化二硫键的形成。 ，我们发现，当成对的 Cys(Acm) 残基在 TFA 中用 PySeSePy 处理时，第二个二硫键自发形成，第二个二硫键的自发形成很可能是由热力学上有利的二硒化物 (PySeSePy) 的形成驱动的。 Cys-S-SePy 加合物。 因此，我们开发了一种在现有二硫键存在的情况下同时脱保护和形成 Cys(Acm) 对的二硫键的一锅法。