After the decalin ring is formed, the chain extension proceeds until the polyketide product is released by the α/β hydrolase BueC. Then, the epimerase BueD is needed for the conversion to the first stable intermediate, 3. The cytochrome p450 BueE catalyses the oxidation of the methyl groups C-1 and 5-Me in 3 to carboxylic acid in 2. The 5-CO2H group is then methylated by BueF to produce 1. The TF BueR and the transporter BueG are likely necessary for the expression and transport of the produced compounds, as they favour higher titres in the context of heterologous expression.