Enantioselective β-Selective Addition of Isoxazolidin-5-ones to Allenoates Catalyzed by Quaternary Ammonium Salts.

The enantioselective addition of isoxazolidin-5-ones to the β-carbon of allenoates has been carried out by using a novel spirobiindane-based quaternary ammonium salt catalyst. This protocol, which proceeds under classical liquid-solid phase-transfer conditions, gives access to unprecedented highly functionalized β-amino acid derivatives with good enantioselectivities and in high yields, and further manipulations of these products have been carried out as well.