Asymmetric Aldols Catalysed by Other Amino Acids and their Derivatives

Asymmetric Aldols Catalysed by Other Amino Acids and their Derivatives 

Chiral diamines derived from natural primary amino acids give up to 99% ee in i yn-selective aldols of linear ketones with aromatic aldehydes, using TFA and 2,4-dinitrophenol as co-catalysts.  

Silyl-protected hydroxyacetone undergoes iyn-selective cross-aldols with various aldehydes in water, using l°-3° diamine catalysts derived from amino acids and bearing a hydrophobic side-chain. Best yield, de, and ee are 94, 82, and 97%, respectively. 

L-/-Leucine catalyses model aldols in moderate to high yields, des, and ees, being superior to leucine, valine, alanine, and proline for the reactions examined. A simple chiral l°-3° diamine (52, derived fl om L-Meucine) and a tungstate (H4SiWj204o) catalyse direct cross-aldols of acetaldehyde, giving 99% yield in 4h, and ee up to 92%.  

Organocatalyst (53) - formed by a one-step 0-acylation of threonine - gives direct aldol y leldldelee up to 99/98/99% in water, can be used on a large scale, and is recoverable and reusable 0-acyl serines with a range of acyl substituents (alkyl, Ph, Bn, CH2CH2Ph) have similar range and reusability in water (up to 99% yield and 0 

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