10-Hydroxy-3,4-dihydroacridine-1,9(2H,10H)-diones, a new group of malaricidal and coccidiostatic compounds

2-Nitrobenzaldehydes and 1,3-cyclohexanediones condense in a mixture of hydrochloric acid and glacial acetic acid to 10-hydroxy-3,4-dihydroacridine-1,9(2H,10H)-diones. Many compounds of this group reveal a pronounced coccidiostatic and malaricidal effect in vivo even against drug-resistant malaria parasites. Synthesis and chemotherapeutic results as well as structure-activity relationships are described.