Chiral Nβ-Fmoc-amino alkyl isonitriles in Ugi-4CR: an assembly of novel 1,1′-iminodicarboxylated peptidomimetics

Enantiopure Nβ-Fmoc-amino alkyl isonitriles and amino acid esters have been employed as building blocks in Ugi four-component reaction (U-4CR) to yield 1,1′-iminodicarboxylated peptidomimetics. By employing trifluoroacetic acid as one of the components, a different outcome has been observed and rationalized. Ugi products are obtained as trifluoroacetamide adducts, which on further reaction under mild acidic conditions lead to the title compounds. The method has also been proven to be useful for the preparation of ethyl, benzyl and tert-butyl esters.