The invention relates to new compounds of the general formula I ##STR1## wherein R.sub.1 is a straight or branched chained alkyl having 1 to 13 carbon atoms, optionally substituted with halogen, alkoxyalkyl containing 1 to 5 carbon atoms in the alkoxy and 1 to 4 carbon atoms in the alkyl moiety or phenyl;R.sub.2 is alkyl having 6 to 20 carbon atoms; alkoxyalkyl, phenoxyalkyl, furfuryl, cyclopropyl-alkyl, cyclopentyl, cycloheptyl, thiazolyl, triazolyl, thiazolinyl, pyridinyl, picolyl, benzimidazolyl, piperonyl, pirimidinyl, chlorobenzothiazolyl, benzyl, phenyl substituted with chloro and/or amino, or amino and alkyl, or amino and nitro groups, alkenyl, alkinyl, aminoalkyl, dialkylamino-alkyl, alkylaminoalkyl, alkylphosphonateammoniumalkyl, 3,5-dichlorophenyl-hidantoinyl, or thiadiazolyl optionally substituted with alkyl;R.sub.3 is hydrogen, phenyl, benzyl, alkenyl, alkyl, hydroxy, alkoxy or alkoxyalkyl; orR.sub.2 and R.sub.3 together stand for a 3,5-dichlorophenyl-hidantoinyl group;R.sub.4 is hydrogen or alkyl optionally substituted with hydroxyl.The new phosphoric acid monoester salts of the general formula I show fungicidal activity. The fungicidal compositions containing said compounds as active ingredients are also within the scope of the invention. According to a further aspect of the invention there is provided a process for the preparation of the new compounds.