Figure 65.

FPP cyclization reactions leading to the formation of major products 5-epi-aristolochene and premnaspirodiene, as well as alternative cyclization products generated by cyclase mutants classified by Noel and colleagues as follows:³⁰⁹ class A products (gray) result from quenching of early carbocation intermediates; class B products (yellow) derive from the eudesmane cation in the absence of any alkyl migrations; class C products (C1, blue; C2, red; C3, green) derive from three different alkyl migrations in the eudesmane cation; and class D products (purple) derive from the (cis,trans)-farnesyl cation. Reprinted with permission from ref (315). Copyright 2016 Macmillan Publishers Ltd.