Efficient stereoconservative syntheses of 4,4-difluoro-2-hydroxybutyric acids from (S)- and (R)-malic and (S)- and (R)-citramalic acid

A preparative simple stereoconservative synthesis of homochiral 4,4-difluoro-2-hydroxybutyric acid and 4,4-difluoro-2-hydroxy-2-methylbutyric acid using hexafluoroacetone as protecting and activating agent is described.