The indole nucleus of Z-Trp-OBzl is modified by acylation of the indole nitrogen using Boc-N-methyl butyric acid followed by catalytic hydrogenation and introduction of the Fmoc group. The resulting derivative, Fmoc-Trp(Boc-Nmbu)-OH, is incorporated into peptide chains via solid-phase peptide synthesis (SPPS). After assembly of the peptide chain, the Boc group is cleaved by treatment with TFA. The peptide is isolated with the tryptophan residue modified with a cationic 4-(N-methylamino) butanoyl group, which improves the solubility of the peptide during HPLC purification. On treatment of the purified peptide at pH 9.5, the Nmbu group undergoes an intramolecular cyclization reaction; this results in the fully deprotected peptide and N-methylpyrrolidone.

中文翻译：

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固相肽合成中色氨酸的新保护基团，可防止酸催化的副反应并有助于通过HPLC纯化

Z -Trp-OBzl的吲哚核通过使用Boc- N-甲基丁酸对吲哚氮进行酰化，然后催化氢化和引入Fmoc基团来修饰。通过固相肽合成（SPPS）将所得的衍生物Fmoc-Trp（Boc-Nmbu）-OH掺入肽链中。肽链组装后，通过TFA处理裂解Boc基团。分离肽，并用阳离子的4-（N-甲基氨基）丁酰基修饰的色氨酸残基改善了HPLC纯化过程中肽的溶解度。在pH 9.5下处理纯化的肽后，Nmbu基团会经历分子内环化反应。这导致完全脱保护的肽和N-甲基吡咯烷酮。