N′-alkylated guanidiniocarbonyl pyrroles:: New receptors for amino acid recognition in water

N'-Substituted guanidinlocarbonyl 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 C > 10(3) M-1) as could be shown by UV titration studies.