- Stereoselective synthesis of spirocyclic oxindoles via prins cyclizations
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The synthesis of spirocyclic oxindole pyran and oxepene frameworks using highly stereoselective Prins cyclizations of homoallylic and bishomoallylic alcohols and isatin ketals is described.
- Paola Castaldi,Troast, Dawn M.,Porco Jr., John A.
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supporting information; experimental part
p. 3362 - 3365
(2009/12/01)
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- An intramolecular Diels-Alder strategy for the asbestinins: Enantioselective total syntheses of 11-acetoxy-4-deoxyasbestinin D and asbestinin-12
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(Chemical Equation Presented) The enantioselective total syntheses of 11-acetoxy-4-deoxyasbestinin D and asbestinin-12 have been completed. A glycolate aldol reaction provided a diene useful for ring-closing metathesis to form an oxonene, which was ultimately employed as a template to execute a highly stereoselective intramolecular Diels-Alder cycloaddition, forming the hydroisobenzofuran moiety. The absolute configuration of the asbestinin subclass was confirmed via these synthetic efforts.
- Crimmins, Michael T.,Ellis, J. Michael
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p. 1649 - 1660
(2008/09/18)
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- Establishing the absolute configuration of the asbestinins: Enantioselective total synthesis of 11-acetoxy-4-deoxyasbestinin D
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A highly stereoselective synthesis of 11-acetoxy-4-deoxyasbestinin D (1) has been completed in 26 linear steps. The synthesis hinges on a selective glycolate aldol addition to establish the C-2 stereocenter, a ring-closing metathesis reaction to complete the oxonene, and an intramolecular Diels-Alder cycloaddition to establish the relative configuration at C-1, C-10, and C-14. This initial total synthesis of an asbestinin also serves to confirm the absolute configuration of this subclass of the C-2-C-11-cyclized cembranoid natural products. Copyright
- Crimmins, Michael T.,Ellis, J. Michael
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p. 17200 - 17201
(2007/10/03)
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- Scope and limitations of the scandium-catalyzed enantioselective addition of chiral allylboronates to aldehydes
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Scandium triflate catalyzes the addition of camphor-derived allyl-, methallyl-, and crotylboronates to aldehydes to provide homoallylic alcohols with excellent diastereo- and enantioselectivity. Aromatic, aliphatic, and propargylic aldehydes can be used successfully in this system. Additional advantages of the camphor-diol allylboronates are their ease of synthesis, their availability in both enantiomeric forms, and their stability towards silica gel chromatography. The usefulness of this methodology is further demonstrated by the gram-scale synthesis of various homoallylic alcohols of high enantiomeric excess and by the concise synthesis of the pheromone (4S)-2-methyloctan-4-ol. 1 Introduction 2 Results and Discussion 2.1 Optimization 2.2 Substrate Scope 2.3 Synthetic Applications 2.4 Mechanistic Considerations 3 Conclusion.
- Gravel, Michel,Lachance, Hugo,Lu, Xiaosong,Hall, Dennis G.
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p. 1290 - 1302
(2007/10/03)
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- A Second-Generation Synthesis of the C1-C28 Portion of the Altohyrtins (Spongistatins)
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A practical second-generation synthesis of an advanced intermediate in our total synthesis of altohyrtin C (spongistatin 2) has been developed. A new approach to the C1-C15 (AB) portion features a vinyllithium addition to an aldehyde followed by a palladium-catalyzed allylic reduction to install the troublesome C13-C15 segment. Our general approach to the C16-C28 (CD) spiroketal has been retained, but some improvements have been made. Most notably, the kinetically controlled CD-spiroketalization reaction now proceeds in high yield with excellent diastereoselection. This new strategy uses the anti-aldol coupling used in our first-generation synthesis to join AB and CD fragments. A total of 9.6 g of intermediate 57 has been produced using this improved route.
- Hubbs, Jed L.,Heathcock, Clayton H.
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p. 12836 - 12843
(2007/10/03)
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- Scandium-catalyzed allylboration of aldehydes as a practical method for highly diastereo- and enantioselective construction of homoallylic alcohols
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A general approach for the allylation of aldehydes using stable, air-tolerant camphor-based chiral allylboronates under Sc(OTf)3 catalysis is described. This practical methodology provides both syn and anti propionate units and other homoallylic alcohols with very high levels of diastereo- and enantioselectivity for several substrates, including functionalized aliphatic aldehydes useful toward the elaboration of complex natural products. Copyright
- Lachance, Hugo,Lu, Xiaosong,Gravel, Michel,Hall, Dennis G.
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p. 10160 - 10161
(2007/10/03)
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