Compounds of formula I ##STR1## and their salts in which n=0 or 1, R.sub.1 and R.sub.2 are each aliphatic or cycloalkyl or NR.sub.1 R.sub.2 is an optionally substituted heterocyclic ring, R.sub.3 is alkyl, cycloalkyl or optionally substituted amino, R.sub.5 is an aliphatic group, R.sub.6 is H, an optionally substituted aliphatic group or a cycloalkyl group, or R.sub.3 and R.sub.5 together with the nitrogen and carbon atoms to which they are attached form an optionally substituted heterocyclic ring or R.sub.5 and R.sub.6 together with the nitrogen to which they are attached form a heterocyclic ring optionally substituted by alkyl and R.sub.7 is optionally substituted alkyl, alkoxy, alkylthio, alkylsulphinyl, alkylsulphonyl, alkoxycarbonyl, trifluoromethyl or cyano have utility as hypoglycemic agents.