This invention provides compounds of formula (I) or its pharmacologically acceptable salt or solvate, wherein A represents aryl or a monocyclic or bicyclic heterocyclic group, R1 represents a halide, nitro, substituted C1-6 alkyl, optionally substituted amino, C1-6 alkyloxycarbonyl, optionally substituted aryl, a heterocyclic group, or heterocyclic carbonyl, R2 represents a hydrogen atom or C1-6 alkyl, R3 represents C1-6 alkyl, all of R4, R5, and R6 represent a hydrogen atom, R7 represents C1-6 alkyl, m is 1 or 2, and n is 1. The compounds are novel lincomycin derivatives having a potent activity against resistant pneumococci. The compounds can be used as an antimicrobial agent and are useful for preventing or treating bacterial infectious diseases.