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 --COCH.dbd.CE--O--, 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, hydroxy, alkyl, halogen, alkenyl, alkoxy, or --NR.sub.1 R.sub.2 in which R.sub.1 and R.sub.2, which are the same or different, are each hydrogen or alkyl, andE is --COOH, a 5-tetrazolyl group or an (N-tetrazol-5-yl) carboxamido group,and pharmaceutically acceptable derivatives thereof.There are also described processes for making the compounds and pharmaceutical, e.g. anti-allergic, compositions containing them.