Chromone Studies. Part 13. Synthesis and Electron-Impact Mass Spectrometric Studies of 5-Hydroxy-2-isopropyl-7-methoxychromone, a Constituent of the Medicinal Plant Baeckea frutescens, and Side-Chain Analogues

5-Hydroxy-2-isopropyl-7-methoxychromone (1d), a chromone constituent isolated from the aerial parts of Baeckea frutescens, and four analogues (1a−c and 1e), all of which exhibit toxicity to the brine shrimp Artemia salina, have been prepared from 2‘,4‘,6‘-trihydroxyacetophenone. High-resolution mass spectrometric analysis has permitted elucidation of the fragmentation patterns exhibited by these systems following electron-impact ionization.