The covalent conjugation of large, functionalized molecules remains a frontier in synthetic chemistry, as it requires rapid, chemoselective reactions. The potassium acyltrifluoroborate (KAT)–hydroxylamine amide-forming ligation shows promise for conjugations of biomolecules under aqueous, acidic conditions, but the variants reported to date are not suited to ligations at micromolar concentrations. We now report that 2-pyridyl KATs display significantly enhanced ligation kinetics over their aryl counterparts. Following their facile, one-step incorporation onto the termini of polyethylene glycol (PEG) chains, we show that 2-pyridyl KATs can be applied to the construction of protein–polymer conjugates in excellent (>95%) yield. Four distinct expressed, folded proteins equipped with a hydroxylamine could be PEGylated with 2–20 kDa 2-pyridyl mPEG KATs in high yield and with near-equimolar amounts of coupling partners. Furthermore, the use of a bis 2-pyridyl PEG KAT enables the covalent homodimerization of proteins with good conversion. The 2-pyridyl KAT ligation offers an effective alternative to conventional protein–polymer conjugation by operating under aqueous acidic conditions well suited for the handling of folded proteins.

中文翻译：

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2-等吡啶基酰基三氟硼酸钾在等摩尔条件下的表达蛋白的聚乙二醇化和二聚化

大的功能化分子的共价缀合在合成化学中仍然是前沿，因为它需要快速的化学选择性反应。酰基三氟硼酸钾（KAT）-羟胺酰胺形成的连接显示了在水性，酸性条件下生物分子缀合的希望，但迄今为止报道的变异体不适合在微摩尔浓度下连接。我们现在报告2-吡啶基KATs显示出比其芳基对应物显着增强的连接动力学。在将它们轻松，一步地整合到聚乙二醇（PEG）链末端之后，我们证明了2-吡啶基KAT可以以优异的产率（> 95％）用于构建蛋白质-聚合物共轭物。四个截然不同的表述，可以用2–20 kDa 2-吡啶基mPEG KAT聚乙二醇化折叠的装配有羟胺的蛋白质，并获得等量的偶联伴侣。此外，使用双2-吡啶基PEG KAT可以实现蛋白质的共价均二聚，并具有良好的转化率。2-吡啶基KAT连接可在酸性水条件下操作，非常适合折叠蛋白的处理，是传统蛋白质-聚合物结合的有效替代方法。