4,4′-Isopropylidine-bis[2-isopropyl]phenol was found to possess antimicrobial activity against gram-positive bacteria and some fungi, whereas it had no effect on gram-negative organisms. The drug has a potent inhibitory action on the synthesis of cell wall mucopeptides of
Bacillus subtilis
by inhibiting the enzyme
d
-glutamate ligase, which is responsible for the incorporation of
d
-glutamic acid into uridine 5′-diphosphate-muramyl-
l
-alanine. The drug had a weak lytic effect on protoplasts and inhibited protein synthesis, whereas no significant effect on the synthesis of deoxyribonucleic acid and ribonucleic acid was found.