An N–S acyl shift reaction of thiol-containing peptides in a trifluoroacetic acid (TFA) solution was confirmed by a combination of 13C NMR spectroscopy, reversed-phase (RP) HPLC, and MS analyses. A model peptide containing a cysteine residue was transformed into an S-peptide in a TFA solution. The S-peptide was quickly transformed to the original peptide during RP-HPLC analysis even when an eluent that contained 0.1% TFA was used. A peptide that had an N-2-mercapto-4,5-dimethoxybenzyl (Dmmb) group was also transformed into an S-peptide, forming a thioester bond with the thiol of the Dmmb group by TFA treatment. The generated S-peptide was isolated by directly injecting the reaction mixture into a RP-HPLC and was readily converted to the corresponding 2-sulfoethyl thioester via an intermolecular thiol exchange reaction with sodium 2-mercaptoethanesulfonate. The 2-sulfoethyl peptide thioester is widely used as a building block in polypeptide synthesis. The N–S acyl shift reaction observed in peptides with or without an auxiliary group provides a new route for the preparation of peptide thioesters.
在
三氟乙酸(TFA)溶液中,通过13C NMR光谱学、反相(RP)高效
液相色谱(HPLC)和质谱分析的组合,证实了含
硫醇肽的N–S酰基移位反应。一个含有半胱
氨酸残基的模型肽在TFA溶液中转化为S-肽。即使在含有0.1% TFA的洗脱液中进行RP-HPLC分析时,S-肽也迅速转变为原始肽。含有N-2-巯基-4,5-二甲氧基苄基(Dmmb)基团的肽也通过TFA处理转化为S-肽,与Dmmb基团的
硫醇形成
硫酯键。生成的S-肽通过直接将反应混合物注入RP-HPLC中分离,并通过与
硫醇
乙磺酸钠的分子间
硫醇交换反应,容易地转化为相应的2-磺乙基
硫酯。2-磺乙基肽
硫酯广泛用作
多肽合成中的构建块。在有无辅助基团的肽中观察到的N–S酰基移位反应为肽
硫酯的制备提供了一条新途径。