[Object]: To provide a compound having a novel structure effective against Hemophilus influenzae and erythromycin resistant bacteria (for example, resistant pneumococci and streptococci) as well as against conventional erythromycin sensitive bacteria. [Solution]: A novel 10a-azalide compound represented by the formula (I), a pharmaceutically acceptable salt thereof or a solvate thereof, or an intermediate for the preparation of the same. The compound of the present invention has superior antibacterial activity against Hemophilus influenzae, erythromycin resistant pneumococci and the like, and therefore, the compound can be used as a therapeutic agent of infectious diseases.