Improved synthetic access to the β,γ-enol ether amino acids, L-2-amino-4-methoxy-trans-but-3-enoic acid and l-2-amino-4-methoxy--but-3-enoic acid

Abstract A synthetic route to L-2-amino-4-methoxy- trans -but-3-enoic acid, exclusive of the cis - isomer, has been developed. The key step is direct formation of a trans -enol ether derivative from the corresponding dimethylacetal, by refluxing in CCl 4 , in the presence of hexamethyldisilazane and Me 3 SiI. The isomeric L- cis amino acid could be accessed from this route by isomerizing the intermediate, methyl DL-2-acetamido-2-amino-4-methoxy- trans -but-3-enoate at 217° C to give cis - trans mixture in a 1:10 ratio.