Compounds of formula (I), wherein R1 and R2 are, independently of one another, H, C1-C6alkyl, C1-C6halogenalkyl, C1-C6alkoxy, C1-C6alkoxy-C1-C6alkyl, or C1-C6alkoxy-C1l-C6alkyloxy, and R3 is C1-C6alkyl, are obtainable in high yields by stereoselective addition of R3-substituted propionic acid esters to R1- and R2-substituted benzaldehydes of formula R—CHO to form corresponding 3-R-3-hydroxy-2-R3-propionic acid esters, conversion of the OH group to a leavaing group, subsequent regioselective elimination to form 3-R-2-R3-propenic acid esters, and their hydrolysis to form corresponding propenic carboxylic acids and their enantioselective hydrogenation, wherein R is (a).