Synthesis and Biological Evaluation of 8-Aminomethyltetracycline Derivatives as Novel Antibacterial Agents

The C-8 position of the tetracyclines has been largely underexplored because of limitations in traditional semisynthetic techniques. Employing a total synthetic approach allowed for modifications at the C-7 and C-8 positions, enabling the generation of structure-activity relationships for overcoming the two most common tetracycline bacterial-resistance mechanisms: ribosomal protection (tet(M)) and efflux (tet(A)). Ultimately, several compounds were identified with balanced activity against both Gram-positive and Gram-negative bacteria, including pathogens bearing both types of tetracycline-resistance mechanisms. Compounds were screened in a murine systemic infection model to rapidly identify compounds with oral bioavailability, leading to the discovery of several compounds that exhibited efficacy when administered orally in murine pyelonephritis and pneumonia models.