Enzyme of the diterpenoid metabolism involved in the biosynthesis of antibacterial oryzalides such as phytocassane. Can use ent-cassadiene as substrate, but not C11-alpha-hydroxy-ent-cassadiene, ent-pimaradiene, ent-sandaracopimaradiene, ent-kaurene, ent-isokaurene, syn-pimaradiene, syn-stemarene, syn-stemodene