The glycosylated macrolactone Fdx was approved in 2011 for the treatment of Clostridioides difficile (C. diff.) infections (CDI), that constitute one of the most common nosocomial infections. Alarmingly, the repertoire of therapeutic options for CDI is very limited, and first Fdx resistant clinical C. diff. isolates have been reported. Furthermore, Fdx has promising in vitro activities against Clostridium perfringens (C. perfringens), Staphylococcus aureus, and Mycobacterium tuberculosis. However, the clinical use is restricted to CDI, mainly due to unfavorable physicochemical properties such as poor aqueous solubility and lack of acid stability. After oral administration, Fdx acts locally in the intestine. While local, intestinal application does not require high solubility and acid stability, these are of critical importance to extend the application portfolio beyond CDI. As such, acid stability is a necessity for gastric application, but also impacts the bioavailability with the membrane permeability of Fdx being higher in the low pH of the stomach. Taken together, the emerging resistance development in CDI, with potential larger applications for other pathogens however limited by poor acid stability and solubility, all provide a strong rational for the development of second generation analogues. Therefore, we aim to synthesize Fdx derivatives via chemical modifications with the main objective to improve its properties. (top) and our strategy to perform a single atom O-/S-exchange in Fdx to access acid stable derivatives (bottom). KRAS G12C : Kirsten rat sarcoma viral oncogene with G12C mutation. KOR k-opioid receptor. VRE: Vancomycin-resistant enterococci. PG Protecting group (acetonide or acetyl).