Biomimetic hydrogen-bonding cascade for chemical activation: telling a nucleophile from a base |
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Authors: | Hyunchang Park Dongwhan Lee |
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Institution: | Department of Chemistry, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826 Korea, |
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Abstract: | Hydrogen bonding-assisted polarization is an effective strategy to promote bond-making and bond-breaking chemical reactions. Taking inspiration from the catalytic triad of serine protease active sites, we have devised a conformationally well-defined benzimidazole platform that can be systematically functionalized to install multiple hydrogen bonding donor (HBD) and acceptor (HBA) pairs in a serial fashion. We found that an increasing number of interdependent and mutually reinforcing HBD–HBA contacts facilitate the bond-forming reaction of a fluorescence-quenching aldehyde group with the cyanide ion, while suppressing the undesired Brønsted acid–base reaction. The most advanced system, evolved through iterative rule-finding studies, reacts rapidly and selectively with CN− to produce a large (>180-fold) enhancement in the fluorescence intensity at λmax = 450 nm.Biomimetic cascade hydrogen bonds promote covalent capture of a nucleophile by polarizing the electrophilic reaction site, while suppressing non-productive acid–base chemistry as the competing reaction pathway. |
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