Structure and absolute configuration of new acidic metabolites from Stachys ehrenbergii

Two novel metabolites have been isolated from the aerial parts of Stachys ehrenberiigii. Their structures and stereochemistry were elucidated using a combination of 13C and 1H homo and heteronuclear 2D NMR experiments and mass analysis. The development of an enantioselective synthesis of 3-(2′-acetoxy-4-phenylbut-3′-enoylamino)propionic acid allowed to confirm the structure and assign the (R) absolute configuration at C-2′ of the natural product.