5. **Proposition of a New Biosynthetic Mechanism**: Based on experimental results and **density functional theory (DFT) calculations**, a new mechanism was proposed for oxetane ring formation. TmCYP1 initiates the reaction by oxidizing the C4(20)-double bond, which then leads to the migration of the C5-acetoxy group to C4 and the formation of the oxetane ring. This mechanism contrasts with previous proposals and underscores the unique role of TmCYP1 in this step of the biosynthesis.