A comprehensive investigation and optimisation on the proteinogenic amino acid catalysed homo aldol condensation

A systematic investigation regarding the application of catalytic amounts of all 20 proteinogenic amino acids in the homo aldol condensation of aldehydes is described obtaining excellent yields of the desired α,β-unsaturated aldehyde. These investigations proved the basic amino acids, lysine and arginine, are effective as organocatalysts, if comparably low concentrations are applied. Through the stepwise and systematic condition alteration, the reaction could be optimised and successfully transferred to other substrates with longer, branched or functionalised alkyl chains. The highest yields are observed with tryptophan as organocatalyst in only 1 h reaction time with TONs of up to 27.

Twenty proteinogenic amino acids were applied as organocatalysts in the homo aldol condensation of aldehydes. Basic amino acids were highly active at low catalyst concentrations and aromatic amino acids generated very good yields in short reaction times. The side-chain groups have no catalytic activity, but they have a big impact on the catalytic activity. A general method was developed, being transferable to other substrates.