Cyclopropane carboxylic acid was fed to Saccharopolyspora erythraea NRRL 18
643 (6-deoxyerythromycin producer), resulting in the production of 6-deoxy-
13-cyclopropyl-erythromycin B. These studies provide further evidence that
deoxyerythronolide B synthase has a relaxed specificity for the starter uni
t.