Synthesis of Highly Enantio-Enriched Heliespirones A and C by a Diastereoselective Aromatic Claisen Rearrangement
Computational methods were used to investigate the stereochemical course of the extra-annular Claisen rearrangement. The stereochemical fidelity of the synthetic strategy and comparison of the optical properties support the hypothesis that the heliespirones are scalemic natural products.
Total synthesis of (-)-heliespirone a and (+)-heliespirone C
Total syntheses of the spiro-epimeric natural products (-)-heliespirone A and (+)-heliespirone C are described. The successful strategy involved an aromatic Claisen rearrangement, a diastereoselective Sharpless asymmetric dihydroxylation (AD) reaction, and an intramolecular oxa-Michael addition.
Norcott, Philip,McErlean, Christopher S. P.
p. 5056 - 5062
(2014/08/18)
Total synthesis of natural enantiomers of heliespirones A and C via the diastereoselective intramolecular Hosomi-Sakurai reaction
A full account of the development of a novel type of the intramolecular Hosomi-Sakurai reactions of the substrates with a pbenzoquinone and an allylsilane moieties connected by an ether linkage is described. This transformation proceeds via an addition-elimination sequence and provides the products with two stereogenic centers through a 1,3(or 1,4)-asymmetric induction in good to excellent diastereoselectivities. A reasonable mechanistic possibility for the reaction, determination of the stereochemistry for the product, and scope and limitation of the transformation are also discussed. The methodology developed here can successfully be applied to the enantiocontrolled total synthesis of the natural enantiomers of (-)-heliespirone A and (+)-heliespirone C, which have been isolated from sunflower Helianthus annuus L. as allelochemicals.