An arginine derivative with a fluorescent side-chain, Boc-Arg(Nap)-OH, was prepared by palladium(0)-catalyzed coupling of Boc-Arg-OH with a 4-bromonaphthalimide. The presence of the fluorophore lowers the pKa of the side-chain guanidinium group by several orders of magnitude, to 9.0 (±0.1), allowing the derivative to access an electrically neutral protonation state that is not generally available to
具有荧光侧链的精
氨酸衍
生物Boc-Arg(Nap)-OH是通过
钯(0)催化Boc-Arg-OH与4-
溴萘二甲
酰亚胺偶联而制得的。荧光团的存在将侧链
胍鎓基团的pKa降低了几个数量级,降至9.0(±0.1),从而使衍
生物可进入精
氨酸本身通常无法获得的电中性质子化状态。计算模型(DFT)预测质子化发生在带有荧光团的侧链C═N原子上。质子化(356 nm)和中性物质(440 nm)的计算电子吸收与实验非常吻合。当用光照射时,从阳离子侧链到适当的碱性溶剂会发生激发态质子转移(E
SPT),导致中性物质发出荧光。