The paper presents the synthesis, characterization and cytotoxicity assessment of five organic compounds containing 4-(phenylsulfonyl)phenyl fragment in the molecule, namely of three acyclic precursors derived from phenylalanine (from N-acyl-a-amino acids, N-acyl-a-amino acyl chlorides and N-acyl-a-amino ketones class) and of the cyclization products: a 1,3-oxazol-5(4H)-one and, respectively, a 1,3-oxazole substituted in position 5 with the p-tolyl group. The synthesized compounds were characterized by spectral methods (UV-Vis, FT-IR, 1H-NMR, 13C-NMR, and MS) and elemental analysis, which confirmed their structures. For the determination of the purity of the new compounds, the RP-HPLC method was used. In view of the therapeutic potential of the newly synthesized compounds, we evaluated their toxicological profile using the Daphnia magna bioassay.