Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin (Germany).
Angew Chem Int Ed Engl. 2015 Dec 7;54(50):15055-9. doi: 10.1002/anie.201505274. Epub 2015 Nov 6.
Native chemical ligation enables the chemical synthesis of proteins. Previously, thiol-containing auxiliary groups have been used to extend the reaction scope beyond N-terminal cysteine residues. However, the N-benzyl-type auxiliaries used so far result in rather low reaction rates. Herein, a new N(α) -auxiliary is presented. Consideration of a radical fragmentation for cleavage led to the design of a new auxiliary group which is selectively removed under mildly basic conditions (pH 8.5) in the presence of TCEP and morpholine. Most importantly and in contrast to previously described auxiliaries, the 2-mercapto-2-phenethyl auxiliary is not limited to Gly-containing sites and ligations succeed at sterically demanding junctions. The auxiliary is introduced in high yield by on-resin reductive amination with commercially available amino acid building blocks. The synthetic utility of the method is demonstrated by the synthesis of two antimicrobial proteins, DCD-1L and opistoporin-2.
天然化学连接能够实现蛋白质的化学合成。以前，含巯基的辅助基团被用于将反应范围扩展到除 N-末端半胱氨酸残基以外的位置。然而，迄今为止使用的 N-苄基型辅助基团导致反应速率相当低。本文提出了一种新的 N(α)-辅助基团。考虑到裂解时的自由基片段化，设计了一种新的辅助基团，在 TCEP 和吗啉存在下，在温和碱性条件（pH 8.5）下选择性去除。最重要的是，与以前描述的辅助基团不同，2-巯基-2-苯乙基辅助基团不仅限于含甘氨酸的位点，并且在空间要求高的连接处的连接也能成功。该辅助基团通过与市售的氨基酸砌块进行树脂上的还原胺化反应以高产率引入。该方法的合成实用性通过两种抗菌蛋白 DCD-1L 和 opistoporin-2 的合成得到了证明。
