Erythromycin A is an antibiotic widely used as an agent for treating infectious diseases caused by Gram-positive bacteria, mycoplasmas, etc. However, erythromycin is decomposed by gastric acid due to its instability to acids, and thus has a drawback of no constancy of movement in the body. Hitherto many erythromycin derivatives have been prepared for the purpose of the improvement of such biological or pharmacological properties. For example, it is reported that 6-O-methylerythromycin A derivatives have an improved stability to acids and have a superior in vivo antibacterial activity in comparison with erythromycin A when administered orally (U.S. Pat. No. 433,803). There are also recent reports relating to 11,12-cyclic carbamate derivatives of erythromycin with the aim of expansion of antibacterial spectrum as well as a stability to acids (EP. patent No. 487411, U.S. Pat. No. 4742049, EP. patent No. 676409 and EP. patent No. 638584), and further reports relating to erythromycin derivatives wherein an acyl group has been introduced at the 3-position (EP. Patent No. 619320).
An object of the present invention is to provide novel antibiotics having a strong antibacterial activity not only against previous erythromycin-sensitive bacteria but also against Haemophilus influenzae and erythromycin-resistant bacteria which recently show a tendency to increase.