The first totalsynthesis of (−)‐euxanmodin B is described. An axiallychiral, enantiomerically pure biphenyl, available by enzymatic desymmetrization of σ‐symmetric biaryl diacetate, was used as the key chiral biaryl building block. Two annulation reactions allowed the construction of the xanthone–anthraquinone compositestructure with full stereochemical control.
While iminium salts generated by the oxidation of amino ketene silyl acetals show intriguing reactivities to give useful γ-oxo-α-amino esters via reactions with silyl enol ethers in good yields, new iminium salts are also prepared by the oxidation of amino silyl enol ethers. They undergo facile addition reaction with various nucleophiles to give α-amino ketone derivatives in good yields.
β-C-2-Deoxyribofuranosides and β-S-2-deoxyribofuranosides are prepared stereoselectively from 1-O-acetyl-5-O-benzyl-3-O-[2-(methylsulfinyl)ethyl]-2-deoxy-d-erythro-pentofuranose or the corresponding 3-O-(2-pyridyl-methyl)pentofuranose N-oxide by the reaction with silyl enol ethers or trimethlsilyl sulfides in the presence of a Lewis acid.
The firsttotalsynthesis of dermocanarin 2 is described. The synthesis features the construction of the anthraquinone and naphthoquinone frameworks through annulation reactions onto an axially chiral biphenyl intermediate, obtained by an enzyme-catalyzed enantioselective desymmetrization of a σ-symmetric precursor, followed by a stereoselective aldol reaction to construct the stereogenic center in
Facile Access to Versatile Polyaromatic Building Blocks: Selectively Protected Benzocyclobutenedione Derivatives via Regioselective [2+2] Cycloaddition of -Alkoxybenzyne and Ketene Silyl Acetal
facile, divergent access to highly oxygenated benzocyclobutene derivatives was developed via the regioselective [2+2] cycloaddition of α-alkoxybenzynes and ketene silyl acetals. The cycloadducts could be converted to selectively protected alkoxybenzocyclobutenediones, an attractive class of compounds for the synthesis of polyaromatic compounds. As one possible application, divergent access to a regioisomer