Fast and Tight Boronate Formation for Click Bioorthogonal Conjugation

Abstract

A new click bioorthogonal reaction system was devised to enable the fast ligation (k(ON) ≈340 m(-1) s(-1)) of conjugatable derivatives of a rigid cyclic diol (nopoldiol) and a carefully optimized boronic acid partner, 2-methyl-5-carboxymethylphenylboronic acid. Using NMR and fluorescence spectroscopy studies, the corresponding boronates were found to form reversibly within minutes at low micromolar concentration in water, providing submicromolar equilibrium constant (K(eq) ≈10(5) -10(6) m(-1)). Efficient protein conjugation under physiological conditions was demonstrated with model proteins thioredoxin and albumin, and characterized by mass spectrometry and gel electrophoresis.

A Panel of TrpB Biocatalysts Derived from Tryptophan Synthase through the Transfer of Mutations that Mimic Allosteric Activation

“…[1f] TmTr pB M145T N167D exhibits substantially faster rates,ranging from 2-to over 7-fold, with substrates that bear electron-withdrawing groups, such as nitro,c yano,f ormyl, and even boronate ( Table 4, entries 3-6), which represents an ew substrate class in the Tr pS literature.T he reaction with 5-boronoindole is particularly interesting since the catalyst must contend with competing proto-deborylation. Boronic acids can serve as handles for bioorthogonal conjugation, [17] pH-sensitive delivery of therapeutics in vivo, [18] and substrates for crosscoupling,t hereby complementing 5-halotryptophans,f or which electron-deficient coupling partners lead to reduced yields. [19] Although the reactivity with these new substrates remains low,w eb elieve that TmTrpB M145T N167D ,w hich only has two mutations compared to six in PfTrpB 0B2 ,i st he ideal parent for further optimization.…”

“…The reaction with 5-boronoindole is particularly interesting, as the catalyst must contend with competing proto-deborylation. Boronic acids can serve as handles for bio-orthogonal conjugation, [17] pH-sensitive delivery of therapeutics in vivo, [18] and substrates for crosscoupling, complementing 5-halotryptophans, for which electron-deficient coupling partners lead to reduced yields. [19] Although the reactivity with these new substrates remains low, we believe that TmTrpB M145T N167D , which only has two mutations compared to six in PfTrpB 0B2 , is the ideal parent for further optimization.…”

N,O‐Iminoboronates: Reversible Iminoboronates with Improved Stability for Cancer Cells Targeted Delivery

“…Iminoboronates are a class of reversible‐covalent based compounds in which an imine is stabilized by the coordination with an adjacent boronic acid . In 2012, we used this strategy to perform the reversible functionalization of the ϵ ‐amino group of lysine residues exposed on the surface of proteins, and later, to generate cancer‐cell‐targeting folic acid fluorescent conjugates .…”

Preise 2016 des Chemical Institute of Canada und der Canadian Society for Chemistry

“…Im Mittelpunkt seines Forschungsprogramms steht die Entwicklung neuer Anwendungen von Organoborsäurederivaten in der Synthese und der Biologie. In der Angewandten Chemie hat er eine bioorthogonale Klick‐Konjugation vorgestellt . Hall gehört dem International Advisory Board des European Journal of Organic Chemistry an.…”