Towards the Synthesis of the Cornexistins

 

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Abstract

A concise synthetic route to the carbocyclic core of the cornexistins is reported. The route is highlighted by a Diels-Alder cycloaddition/oxidative cleavage strategy to generate the central highly functionalized nine-member ring. A silyl-tethered ring-closing metathesis strategy is utilized to control trisubstituted alkene geometry.

References

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Aldehyde 5 was derived from the monoprotection of propane-1,3-diol (BuLi, TBSCl, THF, -78 °C to reflux) and TEMPO/bleach oxidation.

Crystal data, selected bond lengths and angles for 3: Formula: C₃₀H₄₄O₇Si, MW = 544.74, a = 10.3090(4) Å, b = 12.2193(5) Å, c = 13.9422(5) Å, α = 70.593(2)°, β = 78.609(2)°, γ = 74.217(2)°, P1, V = 1582.90(11) ų, Z = 2, R ₁ = 0.0588, wR ₂ = 0.1815. Data collection: 0.5° φ and ω scans, CCD area detector. Solved by direct methods and refined by full-matrix least-squares refinement against F ². Selected bond lengths (Å): O2-C1: 1.429(4), C2-C3: 1.497(4), C8-C9: 1.525(5), C1-C2: 1.499(4), C3-C28: 1.542(4). Selected bond angles (°): C1-O2-C16: 112.5(3), O2-C1-C2: 111.2(3), O2-C1-C9: 113.5(3), C2-C1-C9: 102.5(3), C2-C3-C4: 110.5(2), C2-C3-C28: 112.6(2), C4-C3-C28: 112.6(2). Details of the crystal structure determination have been deposited with the Cambridge crystallographic Data Centre and may be retrieved at www.ccdc.cam.ac.uk by citing CCDC 642483.