There are described compounds of formula I, ##STR1## in which an adjacent pair of R.sub.5, R.sub.6, R.sub.7 and R.sub.8 form a chain --CZC(G.sub.1).dbd.(G.sub.2)--Z--,R.sub.4, R.sub.9 and the remainder of R.sub.5, R.sub.6, R.sub.7 and R.sub.8, which may be the same or different, each represent hydrogen, alkyl, halogen, alkenyl, --NO.sub.2, --NR.sub.1 R.sub.2, --OR.sub.3, --S(O).sub.n R.sub.3 ; or alkyl substituted by hydroxy, amino, alkoxy or carbonyl oxygen,n is 0, 1 or 2,R.sub.1 and R.sub.2, which may be the same or different, each represent hydrogen, alkyl, --CONHR.sub.3, phenyl or phenyl substituted by alkyl or halogen, or R.sub.1 and R.sub.2 together with the nitrogen atom to which they are attached form a 5 or 6 membered heterocyclic ring,R.sub.3 represents hydrogen, alkyl, alkenyl or phenyl,one of G.sub.1 and G.sub.2 is hydrogen and the other is a group E,each E, which may be the same or different, is --COOH, a 5-tetrazolyl group, or a carboxamidotetrazole group,each Z, which may be the same or different, is oxygen or sulphur, andone or two of the atoms, a, b, c and d are nitrogen atoms and the remainder are carbon atoms, R.sup.9 having no significance when two of a, b, c and d are nitrogen,(with certain exclusions)and pharmaceutically acceptable derivatives thereof.There are also described methods for making the compounds and pharmaceutical, e.g. anti-allergic, compositions and mixtures containing them.