## 3 Discussion
Intramolecular cyclization of \(N\)-(1-aryl-1-oxopropanol-2-yl)-4-(4-X-phenylsulfonyl)benzamides afforded the corresponding 1,3-oxazoles, which were inactive in the tested concentration range, with the exception of 2-[4-[(4-bromophenyl)sulfonyl]phenyl]-5-(2,4-dimethylphenyl)-4-methyl-1,3-oxazole **6i** and 2-[4-[(4-bromophenyl)sulfonyl]phenyl]-5-mesity-1-4-methyl-1,3-oxazole **6j**, which showed antifungal action on _C. albicans_ 128 (MIC = 14 \(\mu\)g/mL). Moreover, **6j** inhibited the formation of biofilm by _B. subtilis_ ATCC 6683 (MBIC = 225 \(\mu\)g/mL) and P. aeruginosa ATCC 27853 (MBIC = 14 \(\upmu\)g/mL), and both 1,3-oxazoles presented antibiofilm effect against _C. albicans_ 128 with an MBIC of 112.5 \(\upmu\)g/mL. These properties were probably a consequence of the presence of a bromine atom in the _para_ position of the arylsulfonylphenyl substituent linked to the C-2 and the _m_-xylyl or meselyl group grafted to the C-5 of the 1,3-oxazole ring. Exertification of 2-[4-(phenylsulfonyl)]benzamideamido]propanoic acid **1a** or ethanolysis of 4-methyl-2-[4-(phenylsulfonyl)]phenyl]-1,3-oxazol-5(4_H_)-one **2a** gave ethyl 2-[4-(phenylsulfonyl)]benzamideamido]propanoate **3a**, which was active on _P. aeruginosa_ ATCC 27853 and _C. albicans_ 128 (MIC = 14 \(\upmu\)g/mL). It exhibited an antibiofilm effect on _P. aeruginosa_ ATCC 27853 (MBIC = 14 \(\upmu\)g/mL), _S. epidermidis_ 756, and _C. albicans_ 128 (MBIC = 112.5 \(\upmu\)g/mL). The conversion of \(N\)-acylated \(\upalpha\)-amino acid **1a** into its ester derivative **3a** led to the appearance of antimicrobial properties. Based on in silico predictions, the obtained product also had a good pharmacokinetic and toxicological profile. Derivatization of the \(N\)-acyl-\(\upalpha\)-amino acid **1a** also led to the ethyl [4-methyl-2-[4-(phenylsulfonyl)]phenyl]-1,3-oxazol-5-yl] carbonate **4a**, which showed antimicrobial activity on _S. epidermidis_ 756 and _B. subtilis_ ATCC 6683 (MIC = 56.2 \(\upmu\)g/mL) and on _C. albicans_ 128 (MIC = 14 \(\upmu\)g/mL). Compound **4a** was also capable of decreasing the biomass of _S. epidermidis_ 756 (MBIC = 56.2 \(\upmu\)g/mL), _P. aeruginosa_ ATCC 27853 (MBIC = 14 \(\upmu\)g/mL), _B. subtilis_ ATCC 6683, and fungal strain _C. albicans_ 128 (MBIC = 112.5 \(\upmu\)g/mL). All three \(N\)-acyl phenylalanine (**1d-f**) and all three corresponding 4_H_-1,3-oxazol-5-ones (**2d-f**) showed antimicrobial and antibiofilm activities. Thus, 3-phenyl-2-[4-(phenylsulfonyl)]benzamideamido]propanoic acid **1d** was active on _E. coli_ ATCC 25922 (MIC = 28.1 \(\upmu\)g/mL and MBIC = 225 \(\upmu\)g/mL) and _C. albicans_ 128 (MIC = 14 \(\upmu\)g/mL and MBIC = 112.5 \(\upmu\)g/mL). In contrast, 4-benzyl-2-[4-(phenylsulfonyl)phenyl]-1,3-oxazol-5(4_H_)-one **2d**, which resulted from the cyclization of \(N\)-acyl-\(\upalpha\)-amino acid **1d**, had an inhibitory effect on Gram-positive bacterium _S. epidermidis_ 756 (MIC = 56.2 \(\upmu\)g/mL). Moreover, **2d** presented antibiofilm action against _S. epidermidis_ 756 (MBIC = 56.2 \(\upmu\)g/mL) and _P. aeruginosa_ ATCC 27853 (MBIC = 14 \(\upmu\)g/mL). The 2-[4-[(4-chlorophenylphenyl)sulfonyl]benzamido]-3-phenylpropanoic acid **1e** showed a broad antimicrobial spectrum on Gram-positive bacterium _S. epidermidis_ 756 (MIC = 56.2 \(\upmu\)g/mL), Gram-negative bacterium _E. coli_ ATCC 25922 (MIC = 28.1 \(\upmu\)g/mL), and fungus _C. albicans_ 128 (MIC = 14 \(\upmu\)g/mL). Compound **1e** presented MBIC values of 56.2 \(\upmu\)g/mL for _S. epidermidis_ 756 and _E. coli_ ATCC 25922, 14 \(\upmu\)g/mL for _P. aeruginosa_ ATCC 27853, and 112.5 \(\upmu\)g/mL for _C. albicans_ 128. These effects were probably a result of the presence of the phenylalanine fragment in the molecule and the chlorine atom in the _para_ position of the arylsulfonylphenyl moiety. Intramolecular transformation of \(N\)-acyl-\(\upalpha\)-amino acid **1e** led to 4-benzyl-2-[4-[(4-chlorophenylophenyl)sulfonyl]phenyl]-1,3-oxazol-5(4_H_)-one **2e**, which exhibited antimicrobial activity only on _E.