The Ugi four-component condensation (U-4CC) between an aldehyde, an amine, a carboxylic acid and an isocyanide allows the rapid preparation of α-aminoacyl amide derivatives. The Ugi Reaction products can exemplify a wide variety of substitution patterns, and constitute peptidomimetics that have potential pharmaceutical applications. This reaction is thus very important for generating compound libraries for screening purposes.
Mechanism of the Ugi Reaction
The mechanism is believed to involve a prior formation of an imine by condensation of the amine with the aldehyde, followed by addition of the carboxylic acid oxygen and the imino carbon across the isocyanide carbon; the resulting acylated isoamide rearranges by acyl transfer to generate the final product.
Phenol Ugi-Smiles Systems: Strategies for the Multicomponent N-Arylation of Primary Amines with Isocyanides, Aldehydes, and Phenols
L. El Kaim, L. Grimaud, J. Oble, Angew. Chem. Int. Ed., 2005, 44, 7961-7964.