Synthesis of Chiralα-Benzyl-β2-hydroxy Carboxylic Acids through Iridium-Catalyzed Asymmetric Hydrogenation ofα-Oxymethylcinnamic Acids

An asymmetric hydrogenation of α-oxymethylcinnamic acids was developed by using chiral spiro phosphine-oxazoline/iridium complexes as catalysts to prepare β2-hydroxycarboxylic acids with high reactivity (TON up to 2000) and excellent enantioselectivity (up to 99.5% ee). By using this highly efficient asymmetric hydrogenation as a key step, a concise total synthesis of natural product homoisoflavone (S)-(+)-4 was accomplished.