Compounds of the formula: ##STR1## wherein R represents hydroxymethyl, alkoxymethyl of 2 to 6 carbon atoms, optionally substituted phenoxymethyl, alkanoyloxymethyl of 3 to 10 carbon atoms, optionally substituted benzoyloxymethyl, alkylsulphonyloxymethyl of 2 to 9 carbon atoms, optionally substituted phenylsulphonyloxymethyl, formyl, aminomethyl optionally substituted by 1 or 2 alkyl groups of 1 to 4 carbon atoms, or hydroxyiminomethyl, and acid addition salts thereof, are useful as rodenticides.