Palladium-Catalyzed Allylic Substitution for the Synthesis of Pericosines

A sequence of vinylalumination of α-substituted aldehydes, ring-closing metathesis (RCM), and palladium-catalyzed allylic substitution was utilized to prepare the biologically active natural products, pericosines, from d-ribose. The anti-adduct of vinylalumination was transformed into pericosine A after RCM, removal of the 4-methoxybenzyl protecting group, and chlorination. The diacetate of the anti-adduct was converted to pericosine C after the palladium-catalyzed, S_N2′-type, allylic substitution. However, an unexpected dimeric product was generated in utilizing this approach to prepare pericosine E.