*4.2. Chemical Synthesis and Analysis*

The oxazol-5-(4H)-ones (Oxas) and the precursors aldehydes were synthesized following a general synthetic reported route: a mixture of the corresponding aldehyde (30–600 μmol scale, 1 equiv.), hippuric acid or derivatives (1 equiv.), sodium acetate (1 equiv.) and acetic anhydride (3 equiv.) in a round-bottom flask was heated under magnetic stirring at 110 ◦C for 2 h [31]. Then, the reaction mixture was cooled to room temperature and the obtained solid was washed with distilled water (2×) and MeOH (4×) and dried under vacuum. If further purification was needed, some of the compounds were recrystallized in a suitable solvent. The purity and structural identification were performed by 1H, 13C NMR and mass spectrometry analyses.
