Compounds are disclosed of formula (I): ##STR1## wherein R.sub.1 is halogen, a C.sub.1-3 alkoxy, R.sub.6 R.sub.7 NCO(CH.sub.2).sub.p --, R.sub.6 CONH(CH.sub.2).sub.p --, R.sub.6 R.sub.7 NSO.sub.2 (CH.sub.2).sub.p --, or R.sub.8 SO.sub.2 NH(CH.sub.2).sub.p -- (where R.sub.6 and R.sub.7 each represents hydrogen or C.sub.1-3 alkyl, R.sub.8 represents C.sub.1-3 alkyl and p is zero or 1);R.sub.2 represents hydrogen or C.sub.1-3 alkyl; R.sub.3 represents hydrogen or C.sub.1-3 alkyl;R.sub.4 and R.sub.5 each represents hydrogen, C.sub.1-3 alkyl or 2-propenyl;A represents --CO-- or --SO.sub.2 --;n represents an integer from 2 to 5; and m represents zero or an integer from 1 to 4; and physiologically acceptable salts and solvates (e.g. hydrates) thereof.The compounds have potent and selective vasoconstrictor activity and are indicated as useful for the treatment of migraine. The compounds may be formulated as pharmaceutical compositions with physiologically acceptable carriers or excipients for administration by any convenient route. Various methods for the preparation of the compounds (I) are disclosed.