Orthogonally protected, carboxy-activated L-homoisoserine, 2-methyl-L-homoisoserine, and homoisocysteine derivatives. New building blocks for peptide and depsipeptide modification

Starting from L-malic, L-citramalic, and rac. thiomalic acids routes to L-homoisoserine, 2-methyl-L-homoisoserine and rac. homoisocysteine have been developed. The new orthogonally protected and carboxy-activated building blocks are GABA as well as α-hydroxy and α-mercapto acid derivatives, suitable for the construction of peptide and depsipeptide surrogates.