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. Author manuscript; available in PMC: 2024 Mar 9.
Published in final edited form as: Chem. 2023 Jan 2;9(3):698–708. doi: 10.1016/j.chempr.2022.12.006

Figure 5. Mechanistic proposal and deuterium labeling support for the cyclization of GGPP into 1.

Figure 5.

(A) 1H-13C HSQC spectra of 1, 1,11-2H2-1, 11-2H-1, and 1-2H-2, respectively. See also Figs. S9, S72, and S74–S76.

(B) Proposed mechanism for the formation of the trans-6,10-bicyclic eunicellane skeleton by AlbS (blue pathway). AlbS mutants yielding shunt products 13 and 14 are also shown (black pathways). The red R group depicts the location of the 1R-2H-labeling experiment.

(C) Structure of 1-2H-2 from the 1R-2H-labeling experiment with Bnd4 supporting a different hydride transfer in the AlbS and Bnd4 mechanisms.

(D) Relative free energies of intermediates and transition state structure in kcal mol−1, calculated at mPW1PW91/6–31+G(d,p)//B3LYP/6–31+G(d,p) level of theory.42–48 Bond distances (in Å) for key steps are listed beside the bond. The conformations depicted here are qualitative; see computed structures for actual conformations.49