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Updated: Apr 25, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Dialdehydes lead to exceptionally fast bioconjugations at neutral pH by virtue of a cyclic intermediate
Pascal Schmidt1, Linna Zhou, Kiril Tishinov
1Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel (Switzerland).
Abstract:
One of the open challenges in chemical biology is to identify reactions that proceed with large rate constants at neutral pH values. As shown here, dialdehydes react with O-alkylhydroxylamines at rates of 500 M(-1) s(-1) at neutral pH values in the absence of catalysts. The key to these conjugations is an unusually stable cyclic intermediate, which ultimately undergoes dehydration to yield an oxime. The scope and limitations of the method are outlined, as well as its application in bioconjugation and a mechanistic interpretation that will facilitate further developments of reactions with alkylhydroxylamines at low substrate concentrations.
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