Synthesis of 3',4'-dideoxy and 3',4',5''-trideoxyribostamycin active against kanamycin-resistant E. coli and P. aeruginosa

Structure-Activity Relationships for 5''-Modifications of 4,5-Aminoglycoside Antibiotics

Modification at the 5''-position of 4,5-disubstituted aminoglycoside antibiotics (AGAs) to circumvent inactivation by the APH(3',5'') class of aminoglycoside modifying enzymes (AMEs) has been widely reported.  Such modifications, however, impact activity against wild type bacteria and affect target selectivity in unpredictable ways thereby hindering drug development.  We present a systematic survey of modifications to the 5''-position of the 4,5-AGAs and of the related 5- O -furanosyl apramycin derivatives. In the neomycin and the apralog series, all modifications were well-tolerated, but other 4,5-AGAs require the presence of a hydrogen bonding group at the 5''-position for maintenance of high antibacterial activity. Though the 5''-amino modification resulted in comparable activity to the parent compounds, reduced selectivity against the human cytosolic decoding A site renders this modification generally unfavorable in paromomycin, propylamycin, and ribostamycin. Installation of a 5''-formamido group and, to a lesser degree, a 5''-ureido group resulted in comparable activity to the parents without the selectivity cost of the 5''-amino modification. The lessons learned from this work will aid in the design of next-generation AGAs capable of circumventing susceptibility to AMEs while maintaining high antibacterial activity and target selectivity.