The preparation of the title compounds was carried out from enantiomerically pure 1-monoesters of (S)-malic acid, which are easily accessible from (S)-malic acid 1 by adopting a literature reported procedure, [11] in which treatment of malic acid with trifluoroacetic acid anhydride furnished the corresponding trifluoroacetate of (S)-malic anhydride (Scheme [1] ). Regioselective opening of the anhydride with one equivalent of anhydrous benzyl or methyl alcohol provided ...