A process for combating pests, especially fungi, which comprises applying to plants, seeds, or their loci, an isoxazolo [5,4-d] pyrimidine derivative having the formula: ##STR1## or a salt or optical isomer thereof, wherein R is alkyl or aralkyl, either optionally-substituted; R.sub.2 is hydrogen or alkyl; R.sub.3 is alkyl, aryl, alkylthio, alkanesulphonyl, alkoxy, aryloxy, cyano or optionally-substituted amino.

Disclosed are compounds of the class of furo[3,2-c]pyridines substituted at the 4-position by an amino function bearing a hydroxy-alkyl nitrate moiety, e.g., 4-[ 4-(2-hydroxyethyl)-1-piperazino]-furo[3,2-c]pyridine nitrate. The compounds have pharmacological activity in animals and are useful, for example, as anti-anginal agents. Also disclosed are the corresponding hydroxy intermediates which are useful in preparation of the nitrates and also as anti-anginal agents or as agents in the treatment of shock.