Ansamycins is a family of secondary metabolites that show antimicrobial activity against many gram-positive and some gram-negative bacteria and includes various compounds among which: streptovaricins and rifamycins.

Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia (especially atypical pneumonias associated with Chlamydia pneumoniae or TWAR), skin and skin structure infections.

Cethromycin (initially known as ABT-773[1][2]) is a ketolide antibiotic undergoing research for the treatment of community acquired pneumonia (CAP)[1][3][4][5] and for the prevention of post-exposure inhalational anthrax, and was given an "orphan drug" status for this indication.

Azithromycin is one of the world's best-selling antibiotics, and is derived from erythromycin; however, it differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring, thus making the lactone ring 15-membered.

Oleandomycin is a macrolide antibiotic. It is synthesized from strains of Streptomyces antibioticus. It is weaker than erythromycin.

Spiramycin is a macrolide antibiotic. It is used to treat toxoplasmosis. Although used in Europe, Canada and Mexico[1], spiramycin is still considered an experimental drug in the United States, but can sometimes be obtained by special permission from the FDA for toxoplasmosis in the first trimester of pregnancy.

Roxithromycin is a semi-synthetic macrolide antibiotic. It is used to treat respiratory tract, urinary and soft tissue infections. Roxithromycin is derived from erythromycin, containing the same 14-membered lactone ring. However, an N-oxime side chain is attached to the lactone ring.

Dirithromycin (Dynabac) is a more lipid-soluble prodrug derivative of 9S-erythromycyclamine prepared by condensation of the latter with 2-(2-methoxyethoxy)acetaldehyde. The 9N, 11O-oxazine ring thus formed is a hemi-aminal that is unstable under both acidic and alkaline aqueous conditions and undergoes spontaneous hydrolysis to form erythromycyclamine.