Actiphenol is a glutarimide antibiotic that exhibits both antifungal and antitumor activity, demonstrating higher potency against pathogens such as coxsackievirus B3, influenza virus A, and herpes simplex virus type 2 than synthetic glutarimide derivatives, and Actiphenol production, along with cycloheximide biosynthesis, is controlled by a single gene cluster encoding an acyltransferase-less type I polyketide synthase in Streptomyces species, highlighting its importance in microbial natural product research.