Syntheses of Siderophore–Drug Conjugates Using a Convergent Thiol–Maleimide System

Three siderophore-drug conjugates (sideromycins) were synthesized by preparation of a maleimide linked derivative of the siderophore desferrioxamine B and reacting the corresponding Ga(3+)-complex with freshly prepared thiol-containing antibiotics: loracarbef, ciprofloxacin and nadifloxacin. The conjugates and their synthetic precursors were tested against a broad panel of bacteria and were found to display Gram-positive selective, growth inhibitory activity (µM) indicating that this approach is suitable for the convergent synthesis and screening of novel sideromycins.