I would like to ask about a terpenoid cyclization in terretonin biosynthesis in a research paper authored by Matsuda et al., Curr. Opin. Chem. Biol. 31, 2016.

It is showed in the paper that

The cyclase trt1 is thought to bind (10’R)-epoxyfarnesyl-DMOA methyl ester (9) in the ‘chair-chair’ conformation, and initiate the sequential ring-forming reaction by protonating the terminal epoxide.

I tried to find the crystal structure of trt1 in literature databases and many journals thus I can gain some insights about the roles of its active sites to substrates but didn't come with any result so I think there hasn't been any attempt on determination of crystal structure of trt1.

How the authors likely come at the proposed mechanism? For me, surely, they have found the homologs of trt1 and they apply similar mechanism from the homologs (from other papers talked about other cyclization modes of similar terpenoids) on that terretonin biosynthesis but I really can't find what homologs they use for. There are many classes of terpene synthase and I can't apply these rich information on this biosynthesis.

Any answer by perspective of organic chemistry, biosynthesis, chemical biology, or even molecular docking simulation insight would be very appreciated.

  • $\begingroup$ I believe this conclusion is based solely on the stereochemistry of the product. If you assume that the ring closures all happen in a single concerted step (to form the intermediate shown in brackets in the reaction scheme), then the substrate must start in a conformation where the atoms are already in a position close to where they are after the new bonds form. $\endgroup$ – Andrew Apr 19 at 12:47

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