Photoswitchable peptides were synthesized by using cysteine- and auxiliary-based native chemical ligation reactions. For this purpose, the two regioisomeric azobenzene building blocks 3,4'-AMPB thioester 1b and 4,4'-AMPB thioester 2b were employed in the ligation reactions. While 4,4'-AMPB requires the 4,5,6-trimethoxy-2-mercaptobenzyl auxiliary to minimize reduction of the diazene unit, 3,4'-AMPB can be used in combination with the 4,5,6-trimethoxy-2-mercaptobenzyl auxiliary as well as the Nα-2-mercaptoethyl auxiliary. Thus, 3,4'-AMPB derivatives/peptides proved to be significantly less prone to reduction by aliphatic and aromatic thiols than were the 4,4'-AMPB compounds.
通过使用半胱氨酸和辅助基于天然化学连接反应合成了光开关肽。为此目的,在连接反应中使用了两个位置异构的偶氮苯基组分3,4'-AMPB硫酯1b和4,4'-AMPB硫酯2b。虽然4,4'-AMPB需要4,5,6-三甲氧基-2-巯基苯甲基辅助基以最小化偶氮烯单元的还原,但3,4'-AMPB也可以与4,5,6-三甲氧基-2-巯基苯甲基辅助基以及Nα-2-巯基乙基辅助基结合使用。因此,3,4'-AMPB衍生物/肽明显不太容易被脂肪和芳香硫醇还原,相比之下4,4'-AMPB化合物更易被还原。