amphenicol amphenicol amphenicols are a class of antibiotics with a phenylpropanoid structure. they function by blocking the enzyme peptidyl transferase on the 50s ribosome subunit of bacteria. chloramphenicol thiamphenicol examples of amphenicols include chloramphenicol, thiamphenicol, azidamfenicol, and florfenicol. the first-in-class compound was chloramphenicol, introduced in 1949. chloramphenicol was initially discovered as a natural product and isolated from the soil bacteria steptomyces venezuelae; however, all amphenicols are now made by chemical synthesis.