macrolide antibiotic dirithromycin The hemi-aminal resulting from the condensation of the erythromycin derivative (9<i>S</i>)-erythromycyclamine with 2-(2-methoxyethoxy)acetaldehyde. As the oxazine ring containing the hemi-aminal group is unstable under both acidic and alkaline conditions, dirithromycin functions as a more lipid-soluble prodrug for (9<i>S</i>)-erythromycyclamine. Administered as enteric coated tablets to protect it from acid catalysed hydrolysis in the stomach, it is used to treat respiratory tract, skin, and soft tissue infections caused by susceptible organisms.