The novel 6-O-methyl tricyclic ketolides TE-802 and its analogs were synthesized by two successive cyclization reactions, 11, 12-cyclic carbamate formation by intramolecular Michael addition and 9, 11-diazaheptene ring construction by intramolecular dehydration reaction. These new tricyclic ketolides exhibited good in vitro antibacterial activity against not only erythromycin-susceptible strains but also erythromycin-resistant Staphylococcus aureus and Streptococcus pneumoniae, which are problematic pathogens of nosocomial and communityacquired respiratory tract infections, respectively.