Synthesis, Fluorescent Properties, and Antimicrobial Activities of Novel Vanillin-Based α-Aminophosphonates

Five novel α-aminophosphonates 1-5 were synthesized from a natural product, vanillin, heterocyclic 2-aminobenzothiazole primary amines, and diisopropyl phosphite in a one-pot Kabachnik-Fields reaction with ionic liquid [bmim][PF6] as a catalyst under heating conditions. The structures of the obtained compounds were elucidated by spectral analysis of 1H-NMR, 13C-NMR, 31P-NMR, IR, and HRMS. The UV spectra of 1-5 were measured in five different solvents. The fluorescent properties of 1-5 were examined at 0.1 μM in methanol, ethanol, acetonitrile, 1,4- dioxane, and ethyl acetate. Antimicrobial results revealed that compound 5 showed antibacterial activity, inhibiting Bacillus subtilis by 72.7% at 2.0 mg/mL. Compounds 1-5 showed higher fungal inhibitory activity than the positive control, fluconazole, at concentrations of 3.125-100 μg/mL.