Breaching the Gram-Negative Fortress: Rational Design of A Sterically Stabilized Siderophore-Beta-Lactam Conjugate Targeting E. coli

Background: The outer membrane impermeability of multidrug-resistant (MDR) Gram-negative bacteria, particularly Escherichia coli, remains a primary barrier to antibiotic efficacy. Overcoming this challenge requires strategies that transcend traditional lipophilicity-driven drug design. Methods: This study presents the rational design and in silico validation of ‘Armored-Trojan-1,’ a novel siderophore–beta-lactam conjugate engineered to exploit the bacterial iron-acquisition pathway. Using a generative in silico approach, we designed a high-affinity catechol siderophore with a beta-lactam warhead. To address the metabolic instability limiting previous "Trojan Horse" candidates, we introduced a sterically hindered alpha-methyl ether linker designed to prevent premature periplasmic hydrolysis. Results: Physicochemical profiling indicates that while the candidate exceeds standard passive diffusion thresholds (TPSA > 190 Ų), its polarity is optimized for active transport via the FhuA receptor. A steric and dimensional compatibility audit demonstrates that the molecule fits within the transporter channel without occlusion. Furthermore, structure-based database analysis validates the candidate as a previously undescribed chemical entity. Conclusion: These findings provide a validated computational blueprint for the development of sterically stabilized conjugates, offering a viable strategy to bypass intrinsic resistance mechanisms in Gram-negative pathogens.