The Friedel-Crafts condensation of 8-hydroxycarbostyril (I) with 2-bromobutyryl chloride by means of AlCl3 in refluxing CS2 gives 5-(2-bromobutyryl)-8-hydroxycarbostyril (II), which by reaction with isopropylamine in isopropanol affords 5-(2-isopropylaminobutyryl)-8-hydroxycarbostyril (III). Finally, this compound is reduced with NaBH4 in methanol.