Chemical synthesis of terpenoids with participation of cyclizations plus rearrangements of carbocations: a current overview

Many terpenoids are biosynthesized after a cascade of cyclizations and rearrangements of carbocations mediated by terpenoid synthases, as exemplified in the biosynthesis of lanosterol. Although several reports of organisms or purified enzymes catalyzing this cascade of reactions in the laboratory have been described, the development of chemical transformations capable of mimicking such tandem cyclizations and rearrangements constitute a formidable challenge for organic chemists. From the very early works of Van Tamelen in the 1960s to our time, we present the Lewis or Brønsted acids-mediated cyclization–rearrangements of carbocations cascades aimed to mimic the action of enzymes. From all the achievements herein presented, the hypothesis of minimal enzymatic participation is reinforced, and this, if confirmed, promises new achievements in this area in the next future.