Biosynthesis of the Non‐canonical C17 Sesquiterpenoids Chlororaphen A and B from Pseudomonas chlororaphis

Chlororaphens A and B are structurally unique non‐canonical C 17 sesquiterpenoids from Pseudomonas chlororaphis that are made by two SAM‐dependent methyltransferases and a type I terpene synthase. This study addresses the mechanism of their formation in isotopic labelling experiments and DFT calculations. The results demonstrate an astonishing complexity with distribution of labellings within a cyclopentane core that is reversely connected to two acyclic fragments in chlororaphen A and B. In addition, the uptake of up to 14 deuterium atoms from D 2 O was observed. These findings are explainable by a repeated late stage multistep rearrangement sequence. The absolute configurations of the chlororaphens and their biosynthetic intermediates were elucidated in stereoselective labelling experiments.