Indole derivatives of the general formula (I) are disclosed: ##STR1## where R.sub.1 is H or an alkyl or alkenyl group, R.sub.2 is H, or an alkyl, alkenyl, aryl, aralkyl or cycloalkyl group; R.sub.3 is H or an alkyl group; R.sub.4 and R.sub.5 are independently H or an alkyl or propenyl group or together form an aralkylidene group; and Alk is an optionally substituted alkylene chain; and their physiologically acceptable salts and solutes. These compounds are potentially useful for the treatment of migraine and may be formulated as pharmaceutical compositions in conventional manner. Various methods for the production of the compounds are disclosed including a Fischer-indole cyclization process.