Next, we attempted the oxidative cleavage of the allenyl moiety to the corresponding ester 16. Although examples for ozonolysis of enol ethers in the presence of less electron-rich olefins have been reported, controlled addition of a solution of ozone, even at -115 °C, resulted in complete degradation of the starting material. Alternatively, enol ethers can be reacted with singlet oxygen leading to dioxetanes, which decompose to the corresponding esters. Singlet oxygen exhibits high chemo-and regioselectivity depending on substitution patterns, conformations and stereoelectronic effects of the substrates. Gratifyingly, when methoxyallene 15 was treated with singlet oxygen generated with tetraphenylporphyrin (TPP) as photocatalyst in a test reaction the product could be isolated. As we experienced scale-up problems on a scale larger than 10 mg, we contemplated the application of flow-chemistry. Recently, we developed a modular, and argon-driven flow platform especially designed for the robustification of late-stage transformations in natural product synthesis. In particular, gas reactions and photoreactions can be significantly accelerated and upscaled in flow. Therefore, we translated the oxidative cleavage of methoxyallene 15 to ester 16 into a flow process. After optimizing reaction parameters, the desired ester 16 was obtained in a slightly higher yield of 64% and a remarkably shorter reaction time of 60 minutes compared with 26 hours in batch (Scheme 4). Most importantly, in flow, this transformation could be conducted on a 56 mg scale providing sufficient material for the final step of the synthesis.