N'-alkylated guanidiniocarbonyl pyrroles: new receptors for amino acid recognition in water

reaction: see text] N'-Substituted guanidiniocarbonyl pyrroles 7 were synthesized for the first time by activation of a Boc-protected guanidiniocarbonyl pyrrole 3 with triflic anhydride and subsequent reaction with a primary amine. These guanidinium cations are efficient receptors for the complexation of amino acid carboxylates even in water (K(assoc) > 10(3) M(-1)) as could be shown by UV titration studies.