Compounds of formula (I) have antibacterial activity: wherein R represents hydrogen or 1, 2 or 3 optional substituents; W is ═C(R1)— or ═N—; R1 is hydrogen or an optional substituent and R2 is hydrogen, methyl, or fluorine; or R1 and R2 taken together are —CH2—, —CH2CH2—, —O—, or, in either orientation, —O—CH2— or —OCH2CH2—; R3 is a radical of formula -(Alk1)m-(Z)p-(Alk2)n-Q wherein m, p and n are independently 0 or 1, provided that at least one of m, p and n is 1, Z is —O—, —S—, —S(O)—, —S(O2)—, —NH—, —N(CH3)—, —N(CH2CH3)—, —C(═O)—, —O—(C═O)—, —C(═O)—O—, or an optionally substituted divalent monocyclic carbocyclic or heterocyclic radical having 3 to 6 ring atoms; or an optionally substituted divalent bicyclic heterocyclic radical having 5 to 10 ring atoms; Alk1 and Alk2 are optionally substituted C1-C6 alkylene, C2-C6 alkenylene, or C2-C6 alkynylene radicals, which may optionally terminate with or be interrupted by —O—, —S—, —S(O)—, —S(O2)—, —NH—, —N(CH3)—, or —N(CH2CH3)—; and Q is hydrogen, halogen, nitrile, or hydroxyl or an optionally substituted monocyclic carbocyclic or heterocyclic radical having 3 to 6 ring atoms; or an optionally substituted bicyclic heterocyclic radical having 5 to 10 ring atoms.