Submonomer Synthesis of Inverse Polyamidoamine (i-PAMAM) Dendrimer Antibacterials

Herein we report that the submonomer method for peptoid synthesis enables access to pure i-PAMAM dendrimers up to 16 amino termini by a divergent solid-phase synthesis using the inexpensive bis(3-trifluoroacetamidopropyl)amine as branching unit. We exemplify this new and efficient approach by a structure-activity relationship study of antibacterial dendrimers obtained by appending the polycationic i-PAMAM dendrimer to a hydrophobic core consisting of either an oligoleucine peptide or an oligo-N-isobutylglycine peptoid. These non-hemolytic dendrimers kill Gram-negative bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii and Escherichia coli as well as the Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) by a non-membrane disruptive mechanism involving aggregation of intracellular content as reported for antimicrobial peptoids.