Reduction of Substituted Δ2-Isoxazolines. Synthesis of β-Hydroxy Acid Derivatives

Article abstract of DOI:10.1021/jo00193a008

Three separate methods are reported for the formation of β-hydroxy acid derivatives from readily available substituted Δ²-isoxazolines.Cycloaddition of 2,2-dimethylpropanenitrile oxide with a variety of olefins followed by reductive cleavage produces α '-tert-butyl β-hydroxy ketones.These are cleaved to β-hydroxy tert-butyl esters by Baeyer-Villiger oxidation with peroxytrifluoroacetic acid.In the second approach, α ',β-dihydroxy ketones are generated via cycloaddition of olefins with the nitrile oxide generated from 2-<(trimethylsilyl)oxy>-2-methyl-1-nitropropane followed by reductive ring opening.Standard periodic acid cleavage gives β-hydroxy acids.Finally, 3-methoxy-substituted Δ²-isoxazolines, readily available via benzenesulfonylcarbonitrile oxide-olefin cycloaddition and methoxide displacement, are directly reduced to β-hydroxy esters.