Achmatowicz approach to the asymmetric synthesis of (+)- and (−)-monanchorin

The full account of our development of a de novo asymmetric total synthesis of (+)-monanchorin has been reported. The optimized synthesis provided access to either enantiomer of the guanidine alkaloid natural product in nine steps from the commodity chemicals furan and caproic acid. The route relied upon the asymmetric Noyori hydrogen transfer reduction of an achiral acylfuran to introduce the absolute stereochemistry. In addition, an Achmatowicz rearrangement, a diastereoselective palladium-catalyzed glycosylation, a reductive amination and an acid-catalyzed bicyclic guanidine mixed acetal formation were used to complete the synthesis.