Gas Chromatography Coupled to Electron Ionization Mass Spectrometry Data

For saturated azlactone **6**, supplementary evidence was obtained by its mass spectrum obtained by GC/EI–MS analysis. The two molecular ions of compound **6** corresponding to bromine isotopes (79Br/81Br) were energetically unstable upon interaction with high-energy (70 eV) electrons and fragmented with the elimination of a molecule of propene. The base peak with *m*/*z* 381 and the corresponding radical cation with *m*/*z* 379 (with a relative abundance of 71.61%) were resulted according to the 79Br/81Br isotopic ratio of ≈1:1. Other characteristic structural fragments of **6** are reported in the Materials and Methods section.
