The enantioselective total syntheses of the marine terpenes fuscol and dysidiolide

This thesis describes enantioselective routes to two marine natural products: the antiinflammatory agent precursor fuscol (1) and the potent antitumor agent dysidiolide (17).;The first enantioselective synthesis of the recently isolated cdc25A protein phosphatase inhibitor dysidiolide is based on the Lewis acid mediated cationic rearrangement of 30. This reaction was used to produce the unusual C-1 quaternary center and endocyclic olefin contained within the novel bicyclic core of 17. Elaboration of the two ring appendages was accomplished efficiently to provide dysidiolide (17).*.;The development of improved methodology for the synthesis of E-trisubstituted olefins is also described, and should have particular applicability to the efficient production of substrates for cationic polyolefin cyclization. Additionally, the cyclization and subsequent rearrangement of several acyclic polyolefins containing 1,2-disubstituted double bonds are presented, along with proposed rearrangement pathways for the observed products. ftn*Please refer to the dissertation for diagrams.;The synthesis of fuscol (1) utilized the enantioselective Ireland-Claisen rearrangement of ester 5 to acid 8 as the key step. This transformation set the initial two stereocenters of the molecule, creating a chiral acyclic platform for subsequent cyclization and elaboration. Additionally, this synthesis utilizes a lithium-liquid ammonia reduction of the phosphorodiamide derivative of a hindered alcohol, and applies the Sharpless asymmetric dihydroxylation to the regioselective oxidation of one among three terminal olefinic bonds.*.