Substituted Xanthones as Antimycobacterial Agents, Part 1: Synthesis and Assignment of 1H/13C NMR Chemical Shifts

A series of substituted xanthones was synthesized in order to prove the hypothesis that electron-withdrawing substituents enhance the antimycobacterial of a QSAR equation with C-13 NMR chemical shifts as antimycobacterial activity of these compounds, which is described ofidependent parameters. The key step of the synthesis is the formation of substituted 2-phenoxybenzoic acids by Ullmann reformation action followed by intramolecular Friedel-Crafts acylation, leading to methyl-, carboxy-, nitro-, cyano-, and aminoxanthones as a test set for QSAR investigations. Spectroscopic data (H-1 and C-13 chemical shifts, IR, UV) of these xanthones are presented and analyzed.Specific shift increments for xanthones depending on the substituent position and on the position of the respective proton/carbon atom as well as additivity rules were developed.