Heterocyclic compounds and pharmaceutical use

A compound, with hypolgycaemic activity, having formula (II) or a pharmaceutically acceptable quaternary ammonium or acid addition salt thereof: (II) wherein X represents oxygen or sulphur; n7 represents zero or 1; R7 represents hydrogen or C1-6 alkyl; R1 and R2 are the same or different and represent hydrogen, C1-6 alkyl, phenyl, benzyl, or C3-6 cycloalkyl; R3 represents hydrogen, C1-6 alkyl, phenyl or benzyl; R4 represents hydrogen or C1-6 alkyl; R5 represents C1-6 alkyl, phenyl optionally substituted with up to 3 groups selected from halogen, C1-6 alkyl, and C1-6 alkoxy; or benzyl optionally substituted with up to 3 groups selected from halogen, C1-6 alkyl and C1-6 alkoxy; or R4 and R5 together represent the remaining members of a 5- or 6-membered ring optionally containing an oxygen, sulphur or additional nitrogen atom and being optionally substituted with C1-6 alkyl, carboxy or C1-6 alkoxycarbonyl; and R6 represents phenyl, optionally substituted with up to 3 groups selected from halogen, C1-6 alkyl, C1-6 alkoxy, C1-6 alkanoyl, C1-6 alkanoyloxy, nitro, hydroxy, amino, substituted amino, carboxy, and C1-6 alkoxycarbonyl.