A facile and efficient multi-gram synthesis of N-protected 5-(Guanidinocarbonyl)-1H-pyrrole-2-carboxylic acids

The synthesis of two versatile building blocks for supramolecular anion binding motifs, 5-(N-Boc-guanidinocarbonyl)-1H-pyrrole-2-carboxylic acid (1) and 5-(N-Cbz-guanidinocarbonyl)-1H-pyrrole-2-carboxylic acid (2) is reported. Using these building blocks, a guanidiniocarbonyl-pyrrole anion binding site can easily be introduced into more complex molecules by using standard amide coupling conditions. Both syntheses can be performed on a multi-gram scale. The products are obtained in pure form and can be stored as solids without decomposition. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).