Synthesis and Structure Elucidation of 1-Aryl-substituted Tetrahydropyridone Derivatives
A series of 1-aryl-1,4,5,6-tetrahydro-4(1H)-pyridones having substituents in 2,3- and 2,3,5-positions was prepared from N-aryl-β-alanines and ethyl acetoacetate or 2,4-pentanedione. Twelve tentative biologically active compounds were identified by the combination of 1H, 13C and 1H/13C NMR spectroscopy. The extensive interest has been focused on the influence of substituents as well as on the number, attachment position, and the nature of the substituents. The unknown shielding of the heterocyclic ring on the aromatic carbon atoms was determined and the averaged chemical shift increments were successfully used for the assignment of the aromatic moiety of the studied compounds. The presence of two chiral elements in compounds 16, 17, 20–21 resulted in the mixture of diastereomers and double sets of the resonances in NMR spectra.