Branching out from the bisabolyl cation. Unifying mechanistic pathways to barbatene, bazzanene, chamigrene, chamipinene, cumacrene, cuprenene, dunniene, isobazzanene, iso-γ-bisabolene, isochamigrene, laurene, microbiotene, sesquithujene, sesquisabinene, thujopsene, trichodiene, and widdradiene sesquiterpenes

Abstract

Quantum chemical calculations on the transformation of the bisabolyl cation into an array of sesquiterpenes (iso-γ-bisabolene, trichodiene, cuprenene, laurene, isochamigrene, chamigrene, chamipinene, sesquithujene, sesquisabinene, microbiotene, dunniene, cumacrene, isobazzanene, bazzanene, barbatene, widdradiene, and thujopsene) are described. The bisabolyl cation is the hub of a complicated web of carbocations involved in the construction of diverse and complex molecular architectures present in a large number of Nature's sesquiterpenoids. The results of quantum chemical calculations on the multitude of rearrangements described herein provide reasonable answers to several persistent mechanistic questions in the world of terpene biosynthesis and also provide examples of general reactivity principles for terpene-forming (and other) carbocation rearrangements.