COMU

Technical Specifications

Product Description & Scientific Applications

COMU ((1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate) is a third-generation uronium-type peptide coupling reagent that pairs the Oxyma (ethyl 2-cyano-2-(hydroxyimino)acetate) leaving group with a dimethylamino–morpholino carbenium cation and a hexafluorophosphate counter-ion. On activation with a tertiary-amine base it converts a carboxylic acid into the corresponding Oxyma active ester, driving fast, efficient amide-bond formation with very low racemisation, comparable to HATU. The morpholino skeleton gives COMU markedly higher solubility than HBTU or HATU — permitting roughly four-fold more concentrated DMF stocks — and acts as an internal hydrogen-bond acceptor, so that coupling proceeds with only one equivalent of base. Its by-products are water-soluble for simple aqueous workup, and the reaction solution changes colour as coupling proceeds, allowing visual or colorimetric monitoring.

Common Scientific Applications

Solid-phase peptide synthesis (Fmoc-SPPS): Widely used for assembling peptides, with coupling rates comparable to HATU and requiring only one equivalent of a tertiary-amine base. It is particularly effective for sterically hindered amino acids and for double couplings of difficult sequences where less reactive reagents can give incomplete conversion, and it performs well under microwave-accelerated protocols.

Solution-phase amide-bond formation: An efficient reagent for solution-phase amide synthesis, including peptidomimetics and the condensation of protected peptide fragments. Its high solubility in DMF and NMP and rapid activation kinetics suit solution-phase coupling, while its water-soluble by-products make aqueous workup straightforward.

Low racemisation and fragment condensation: COMU delivers among the lowest epimerisation levels reported for uronium reagents; in standard racemisation test models such as the Young test and the Z-Phg-Pro-NH2 model it suppresses epimerisation as effectively as HATU and more effectively than HBTU at the activated stereocentre. Its low epimerisation and rapid activation make it well suited to segment condensation, where prolonged activation of a C-terminal residue would otherwise promote loss of configuration.

Reaction monitoring and practical handling: The colour change of the coupling solution lets the reaction be followed visually or colorimetrically without sampling, a convenient feature on both manual and automated peptide synthesisers. Because COMU solutions have a more limited shelf-life than carbodiimide/Oxyma systems, working solutions are best prepared fresh.

Amide and ester bond formation beyond peptides: Beyond peptide chemistry, COMU activates carboxylic acids for amide and ester bond formation in general organic synthesis.

Further Reading

For guidance on selecting between carbodiimides, aminium/uronium salts, phosphonium salts, and other reagent classes for amide and peptide bond formation, see NorrChemica's Lab Journal guide: Choosing a Coupling Reagent for Amide and Peptide Bond Formation.

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