Asymmetric 1,4-Additions to 5-Alkoxy-2(5H)-furanones Enantioselective Synthesis and Absolute Configuration Determination of β-Amino-γ-butyrolactones and Amino Diols

The synthesis of enantiomerically pure β-amino-γ-butyrolactones via asymmetric conjugate addition of various amines to 5-menthyloxy-2(5H)-furanone is described. This route provides access to new multifunctional homochiral building blocks. The absolute configuration of the β-amino-γ-butyrolactones is established by X-ray analysis and 1H NMR correlation. The conjugate addition of amines to 2[5H]-furanone, 5-alkyl-2[5H]-furanones and 5-alkoxy-2[5H]-furanones was studied and an enhanced reactivity was observed in 2[5H]-furanones due to a γ-alkoxy-effect. The synthetic utility of the asymmetric amine addition is illustrated in an efficient route to various optically pure 2-amino-1,4-butanediols