Isolated from the bacterium Streptomyces clavuligerus. The 1-proR hydrogen atom of geranylgeranyl diphosphate is involved in a 1,3-hydride shift to the side-chain. The enzyme also produces hydropyrene, hydropyrenol, and traces of other diterpenoids. cf. EC 4.2.3.201, hydropyrene synthase, and EC 4.2.3.202, hydropyrenol synthase.