One-Pot Sequential Aerobic Oxidation/1,3-Dipolar Cycloaddition/α-Iminol Rearrangement of 1-Benzyl-3,4-dihydroisoquinolines with Iso(thio/seleno)cyanates: A Facile Synthesis of Tetrahydroisoquinoline-Fused-(Thio/Seleno)Hydantoin Derivatives

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) (1) was reacted with L‐phenylalanine (2) in a mixture of acetic acid and pyridine (3 : 2) at room temperature, then was refluxed at 90–100°C and N,N′‐(Pyromellitoyl)‐bis‐L‐phenylalanine diacid (3) was obtained in quantitative yield. The imide‐acid (3) was converted to N,N′‐(Pyromellitoyl)‐bis‐L‐phenylalanine diacid chloride (4) by reaction with thionyl chloride. Rapid and highly efficient synthesis of poly(amide‐imide)s (6a–f) was achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of N,N′‐(Pyromellitoyl)‐bis‐L‐phenylalanine diacid chloride (4) with six different derivatives of 5,5‐disubstituted hydantoin compounds (5a–f) in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly, compared with the conventional melt polycondensation and solution polycondensation, and was almost completed within 10 min, giving a series of poly(amide‐imide)s with inherent viscosities about 0.28–0.44 dL/g. The resulting poly(amide‐imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analyses, inherent viscosity (ηinh), solubility test and specific rotation. Thermal properties of the poly(amide‐imide)s were investigated using thermal gravimetric analysis (TGA). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 516–524, 2004

A new series of hydantoin derivative dimers as potential broad-spectrum antibiotic agents is designed and synthesized to combat ESKAPE pathogens. As membrane-active antimicrobial agents, in addition to cationic charged and hydrophobic groups that mimic AMPs (antimicrobial peptides), hydantoin backbones and aromatic linkers increased the rigidity and lipophilicity of the designed compounds, thus improving the stability and bactericidal killing rate. After whole cell phenotypic screening against eight bacterial strains, including MRSA (methicillin-resistant S. aureus), compound 18 was chosen as the lead compound with overall excellent broad-spectrum antibacterial activity (GM = 7.32 μg mL-1) and good selectivity. Kill-kinetic studies of compound 18 showed that the bacterial growth of both Gram-positive and Gram-negative was completely inhibited within one hour, which demonstrated excellent sterilization efficiency of 18. Furthermore, drug resistance and mechanism studies showed that compound 18 exhibited a steady antibacterial performance during 25 passages and could disrupt bacterial cell membrane integrity and cause cell death. Along with the facile synthesis procedures in solution, this series of hydantoin derivative dimer compounds could be an appealing next generation of antibiotic agents to combat emergent drug resistance.