The invention relates to a novel method for synthesizing bis(2-hydroxyaryl)aminoacetic acids with a high degree of purity and good yield. Said compounds can be used as ligands to obtain iron chelates that can be applied as micronutrient fertilizers in agriculture. The method is based on the use of trimethylsilyl cyanide (TMSCN) in a modified Strecker synthesis. Due to their high degree of purity, the ligands obtained through said method can be used as stocks for the analysis and quantification of commercial chelates.