Abstract: A series of vancomycin C-terminus guanidine modifications are disclosed that improve antimicrobial activity, enhance the durability of antimicrobial action against selection or induction of resistance, and provide two synergistic mechanisms of action independent of D-Ala-D-Ala binding that cause inhibition of cell wall biosynthesis, while inducing bacterial cell permeability. A contemplated compound contains two combined peripheral modifications, a (4-chlorobiphenyl)methyl (CBP) and C-terminus guanidine modification, that provide new treatments against not only vancomycin-sensitive, but especially vancomycin-resistant bacteria. The data demonstrate that the synergistic behavior of the peripheral modifications requires the presence of both the CBP and guanidine modifications in a single molecule versus their combined use as an equimolar mixture of singly modified compounds.