Construction of the Polycyclic Structure of Mangicols from Chiral Propargylic Alcohols

Chiral propargylic alcohols are versatile synthetic components in asymmetric synthesis. The asymmetric alkynylzinc addition to aldehydes is an efficient method to access chiral propargylic alcohols. Pauson-Khand cyclization-based domino reactions of chiral propargylic alcohol derivatives can conveniently construct the multicyclic structure of complex molecules.
Mangicols, isolated from the marine fungus Fusarium heterosporum by Fenical and coworkers in 2000, are new type of sesterterpenoid metabolites with unprecedented spirotricyclic skeletal components. They represent a novel class of multicyclic natural products that could potentially be made by using the transformations of chiral propargylic alcohols.
A one-pot Rh-catalyzed domino intramolecular Pauson-Khand reaction and [4+2] cycloaddition was developed to generate an optically active polycyclic compound possessing the core fragment of mangicols. Other related polycyclic compounds were also synthesized through the same strategy. Further conversions of the polycyclic compound were investigated to facilitate the synthesis of mangciols.