The invention relates to antibacterial compounds of formula I wherein R1 represents alkoxy or halogen; U, V and W each represent CH, or one of U, V and W represents N and the others each represent CH; A represents CH2 or O; G is CH═CH-E wherein E represents a phenyl group mono- or di-substituted with halogen, or G is a group of one of the formulae hereafter wherein Z represent CH or N, Q represents O or S and K represents O or S; and salts of such compounds.