Carbonyl Activation in Electrophilic Polyene Cyclizations: A Toolbox for the Design of Isoprenoid Libraries. Issue 27 (5th June 2017) - Minassi, Alberto
Abstract: An approach to biogenetically overlooked areas of the isoprenoid chemical space is presented. This strategy is based on the generation of a cationic center in functionalized polyolefins by Lewis acid activation of a carbonyl group, rather than by electrophilic attack at a double bond. Starting from the monocyclic humulane trienone zerumbone, polycyclic sesquiterpenoid skeletons which are either not reported as natural products or biogenetically enigmatic in terms of the isoprenoid rule, were obtained by modulating the Lewis acid catalyst. In the course of these studies, the surprising formation of a strained E ‐cyclooctene motif was observed in a cyclization reaction. Abstract : Exotic but inhabited : The vast area of the putative isoprenoid chemical space was investigated by cyclizing the humulane dienone zerumbone under carbonyl, rather than olefin, activation. Novel reaction avenues of biogenetic and mechanistic relevance were discovered, thus providing a clue to the enigmatic stenotarsane skeleton and documenting the formation of the strained E ‐cyclooctene motif in a cyclization reaction.