title: Stereocontrolled asymmetric synthesis of syn-E-1,4-diol-2-enes using allyl boronates and its application in the total synthesis of solandelactone F.
abstract: The solandelactones A-H comprise a novel class of oxygenated fatty acids bearing an eight-membered lactone, trans cyclopropane, and a 2-ene-1,4-diol subunit. The relative stereochemistry of the 1,4-diol subunit is anti in solandelactones A, C, E & G, and syn in solandelactones B, D, F & H. Having prepared one member of the solandelactones bearing anti stereochemistry (solandelactone E), we have targeted the syn series and developed methodology for the synthesis of enantioenriched syn-2-ene-1,4-diols. The methodology comprises asymmetric deprotonation of an alkyl 2,4,6-triisopropylbenzoate using sBuLi/sparteine, followed by addition of the α-lithiobenzoate to β-silyl vinyl boronic acid ethylene glycol ester. The boron-ate complex generated undergoes a 1,2-metallate rearrangement furnishing an intermediate allyl boronic ester which is trapped by an aldehyde in the presence of MgBr(2) to furnish anti-β-hydroxy E-allylsilanes in good yields, high diastereoselectivity and high enantioselectivity. These sensitive products were oxidized using mCPBA to the corresponding epoxides and subsequently treated with acid to furnish syn-E-2-ene-1,4-diols (~4:1 d.r.). Application of the methodology to appropriately functionalized aldehyde and ω-alkenyl 2,4,6-triisopropylbenzoate coupling partners, led to a short, highly selective route to solandelactone F (bearing a syn-E-2-ene-1,4-diol).
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK BS8 1TS.
authors.forename: Anna
authors.initials: A
authors.lastname: Robinson
authors.forename: Varinder K
authors.initials: VK
authors.lastname: Aggarwal
mesh_terms: D000475:Alkenes / Q000737:chemistry; D001897:Boronic Acids / Q000737:chemistry*; D015777:Eicosanoids / Q000138:chemical synthesis*; D004852:Epoxy Compounds / Q000737:chemistry; D007783:Lactones / Q000138:chemical synthesis*; D015394:Molecular Structure; D012821:Silanes / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D001897:Boronic Acids; D015777:Eicosanoids; D004852:Epoxy Compounds; D007783:Lactones; D012821:Silanes; C511847:allylsilane; C523382:solandelactone F