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

5-Hydroxy-2-isopropyl-7-methoxychromone (<b>1d</b>), a chromone constituent isolated from the aerial parts of <i>Baeckea frutescens</i>, and four analogues (<b>1a</b>−<b>c</b> and <b>1e</b>), all of which exhibit toxicity to the brine shrimp <i>Artemia salina</i>, 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.