Late-Stage Functionalization of the Rifamycin Core via Click Chemistry Toward New Antibacterial Derivatives

Area of Science:

• Medicinal Chemistry
• Organic Synthesis
• Natural Product Chemistry

Background:

• Antimicrobial resistance (AMR) is a major global health threat, driven by pathogens like multidrug-resistant tuberculosis (MDR-TB) and methicillin-resistant Staphylococcus aureus (MRSA).
• Rifamycins are essential antibiotics, but their efficacy is declining due to increasing resistance.
• Novel strategies are needed to develop new rifamycin derivatives that overcome existing resistance mechanisms.

Purpose of the Study:

• To establish a versatile, click-enabled platform for synthesizing C8-functionalized rifamycins.
• To generate diverse novel antibacterial scaffolds, including 3'-hydroxy-5'-aminobenzoxazinorifamycins (bxRifs) and 25-deacetylated rifamycins (deAcRifs).
• To facilitate late-stage analog development of the complex rifamycin S natural product.

Main Methods:

• Installation of azido and alkyne functionalities onto the rifamycin core.
• Copper(I)-catalyzed click chemistry to form 1,2,3-triazole linkages.
• Development of systematic High-Performance Liquid Chromatography (HPLC) methods for purification of complex analogs.

Main Results:

• Successful synthesis of a library of C8-modified rifamycin analogs.
• Demonstrated conversion of functionalized rifamycins into bxRifs and deAcRifs.
• Identified distinct antibacterial profiles of the synthesized analogs, particularly against Gram-positive bacteria including MRSA and Streptococcus mutans.

Conclusions:

• The developed click chemistry platform provides modular access to novel rifamycin scaffolds, expanding beyond traditional modifications.
• This strategy enables rapid diversification for combating antimicrobial resistance and discovering new antibacterial agents.
• The findings inform structure-activity relationships and lay the groundwork for future bioorthogonal applications in drug discovery.