Fortunately, we successfully obtained single crystals of all four oxidative products using different solvent combinations (Supplementary Table ), allowing us to determine their absolute stereochemistry through X-ray diffraction, with three of them being suitable for absolute stereochemistry determination (Fig. ). As a result, the absolute configuration of compound 1 was unambiguously determined to be 1S, 10S, 14S, 2Z, 6E (Fig. ). This is the first successful report of determining the absolute stereochemistry of enzyme-synthesized eunicellane diterpenes by obtaining a series of excellent single crystals.