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PyOxim® is a novel and highly efficient coupling reagent which mediates coupling reactions with efficiencies superior to HATU and PyBOP® and comparable to COMU®.

CAS: 153433-21-7

Synonym: [Ethyl cyano(hydroxyimino)acetato-O2]tri-1-pyrrolidinylphosphonium hexafluorophosphate




Molecular Formula


Molecular Weight

527.38 [gr/mol]


White crystalline powder

Storage Conditions

Store in a cool and dry place (2-8oC)


  • It has excellent solubility in DMF and is stable in solution under an inert atmosphere for two days.
  • PyOxim® shows higher stability in acetone and DMF than all benzotriazole counterparts, consequently standing out as promising choice for cyclization.
  • Furthermore, PyOxim® is safer to handle and less allergenic than HOBt-based coupling reagents, and it is not explosive under normal operating conditions.


  • PyOxP and PyOxB: the Oxyma-based novel family of phosphonium salts
    Ramon Subir´os-Funosas, Ayman El-Faham and Fernando Albericio Org. Biomol. Chem., 2010, 8, 3665–3673.
    Read Article
  • Fast conventional Fmoc solid-phase peptide synthesis: a comparative study of different activators
    Christina Ann Chantell, Michael Abayomi Onaiyekan and Mahendra Menakuru J. Pept. Sci. 2012; 18: 88–91.
    Read Article


Solid phase peptide synthesis of ‘difficult sequences’ using Pyoxim

Erik Holm Nielsen and Troels Skrydstrup

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Evaluation of the “ResPep continuous flow synthesizer” with real-time UVmonitoring,
automated feedback & heating in solid phase peptide synthesis

Felix Niethammer, Daniel Maisch, Marcus Rothe
INTAVIS Bioanalytical Instruments AG

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