Efficient asymmetric synthesis of unnatural beta-amino acids

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.