The simple and highly enantioselective methanolysis of cyclic meso-anhydrid
es mediated by cinchona alkaloids leads to a broad variety of dicarboxylic
acid mono-methyl esters with up to 99% ee. From these products, unnatural A
f-protected P-amino esters can be obtained by means of Curtius degradation
of the corresponding acyl azides. Subsequent cleavage of the protecting gro
ups leads to the free beta -amino acids in excellent yields, By enantiomer
differentiating opening of racemic anhydrides, synthetically highly useful
regioisomeric amino acid esters become readily available.