Abstract:

A ring-expansion synthesis from bicyclical enol-ethers can lead to surprises. From a standard procedure to synthesize (±)-pirenophorin, a unique molecule has been found, a diisoxazoledilactone (Figure 1). Racemic mixtures as dioximedilactones, diketodialctones and diisoxazoledilactone were observed on intermediate steps. Its components were characterized by chromatographic and spectrometric methods. In order to explain the formation of the oxazolinic rings, molecular dynamics (MD), Austin Model 1 (AM1) , density functional theory (DFT) and AM1 13C NMR simulations were performed in order to characterize stereochemistry of the intermediates and to verify if it is possible to predict isomerism from the chemical shifts variations by AM1.