The garuganin and garugamblin diarylether heptanoids: total synthesis and determination of chiral properties using dynamic NMR

Abstract

The synthesis of the garuganin and garugamblin diarylether heptanoids using an intramolecular Ullmann coupling is reported. Alkene stereoisomers, vinylogous ester regioisomers, and β-diketone congeners are also synthesized. The chiral properties and free energies of activation for racemization of the garuganin and garugamblin diarylether heptanoids and congeners are determined using dynamic NMR methods. A combination of techniques including coalescence measurements, line shape analysis, and selective inversion experiments are used to measure racemization barriers. None of the garuganin or garugamblin diarylether heptanoids are chiral, despite their reported specific rotation values.