Natural amino acids represent an easy accessible, cheap and optically pure source for the synthesis of chiral (ionic) liquids, organocatalysts or ligands in asymmetric organometallic catalysis. Here we present a general synthesis for chiral, biogenic imidazolium salts by condensation of amino acids, glyoxal and formaldehyde in water. Esterification of these NHC-precursors with alcohol and (CH3)3SiCl quantitatively yields the corresponding di-esters (NHC �HCl ), which have been converted to a broad range metal complexes via the established silver transfer route.A broad range of complexes were tested for their catalytic and cytostatic activity revealing a surprisingly pronounced dependence on the nature of the amino acid side chain. Alanine-derived palladium complexes at 10-3 mol-% were found to generate up-to quantitative conversion in aqueous Suzuki-Miyaura cross-coupling reactions within 15 minutes at 100 �C using microwave heating. In HeLa and PC3 cell based anti-cancer activity studies therapeutically interesting IC50 concentrations<10�M were found for Leucin-derived compounds.

Transition metal complexes of chiral N-heterocyclic carbene ligands derived from amino acids: Applications as catalysts and anti-tumour agents

243rd National Meeting (2012)

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