Abstract: Compounds of the formula ##STR1## wherein X and Y, which may be identical to or different from each other, are each hydrogen or halogen,R.sub.1 is hydrogen or straight or branched alkyl of 1 to 4 carbon atoms,R.sub.2 is hydrogen, straight or branched alkyl of 1 to 3 carbon atoms, carboxy-lower alkyl or acyl, preferably lower aliphatic carboxylic acyl,R.sub.3 is hydrogen or acyl, preferably lower aliphatic carboxylic acyl, andn is 1 or 2;non-toxic, pharmacologically acceptable acid addition salts thereof; sulfonium salts thereof; and, when R.sub.1 is hydrogen, salts thereof formed with inorganic or organic bases or basic aminoacids. The compounds as well as their various salts are useful as mucolytics.