Katsuhide Okada,l James A. Kelley, and John S. Driscoll* ... Drug Design & Chemistry Section, Laboratory of Medicinal Chemistry & Biology, Drug Research & Development Program, Division of Cancer Treatment, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014 Received February 7, I977 ... Reaction of 5,5-diphenyl-Z- thiohydantoin with 1-bromo-2-chloroethane generated two isomeric imidazo- [2,1-b] ...