Figure 2.

Relative free energies of intermediates and transition state structures in kilocalories per mole, calculated with mPW1PW91/6–31+G(d,p) (see the Supporting Information for details). Yellow numbers are relative energies for minima, and blue numbers are relative energies for transition state structures. Note that the isoprenyl diphosphate tail was truncated to a methyl group for these calculations [R = CH₃ rather than R = CH₂CH₂C(CH₃)=CHCH₂OPP was used].