- Catalytic enantioselective approach to the eudesmane sesquiterpenoids: Total synthesis of (+)-carissone
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(Chemical Equation Presented) A catalytic enantioselective approach to the eudesmane sesquiterpenoids is reported. The strategic use of a palladium-catalyzed enantioselective alkylation of vinylogous ester substrates forged the C(10) all-carbon quaternary
- Levine, Samantha R.,Krout, Michael R.,Stoltz, Brian M.
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supporting information; experimental part
p. 289 - 292
(2009/08/08)
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- SUBSTITUTED FLUOROETHYL UREAS AS ALPHA 2 ADRENERGIC AGENTS
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Therapeutic compounds, and methods, compositions, and medicaments related thereto are disclosed herein.
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Page/Page column 44
(2008/12/04)
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- Remarkable effect of aluminum reagents on rearrangements of epoxy acylates via stable cation intermediates and its application to the synthesis of (S)-(+)-sporochnol A
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A remarkable effect of (C6F5O)3Al for promoting the rearrangement of epoxy acylates via stable cation intermediates was found, and new methods for constructing chiral benzylic, vinylic, and acetylenic quaternary carbon centers were developed. During the study, the importance of the ionic nature of the O - metal bond in the intermediates of such epoxides was addressed. This method was applied to the asymmetric total synthesis of (S)-(+)-sporochnol A.
- Kita,Furukawa,Futamura,Ueda,Sawama,Hamamoto,Fujioka
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p. 8779 - 8786
(2007/10/03)
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- Application of palladium-catalyzed [3 + 2] cycloaddition technology to the elaboration of kempane diterpenes. Stereocontrolled Synthesis of (±)-3α-hydroxy-7β-kemp-8(9)-en-6-one and (±)-3β-hydroxykemp-7(8)-en-6-one
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The total synthesis of three hydroxykempenones (8-10) has been accomplished. The retrosynthetic elements of the strategy focused on setting four key stereocenters in rings A and B, followed by annulation of ring C and ultimate cyclization to construct the seven-membered ring, D. Since the target molecule carries eight contiguous stereogenic centers, proper attention to stereocontrolled processes was mandatory. The key features of the scheme include the palladium-catalyzed [3 + 2] cycloaddition of trimethylenemethane to an activated octalone with complete control of π-facial selectivity, fully regiospecific monooxidation of a diol with ammonium molybdate uniquely at the secondary site to provide a key hydroxy ketone, hydroxyl-directed hydride reduction of the latter intermediate in order to override a contrary kinetic preference for nucleophilic attack, avoidance of Grob fragmentation in diaxial, monofunctionalized 1,3-diols, and selective deoxygenation of a 1,3-diol. The stereochemical results featured in the cycloaddition step were elucidated preliminarily in experiments designed to probe cyclopentannulation in general. The striking kinetic stability of the α,β- and β,γ-unsaturated tetracyclic end products has been analyzed by means of molecular modeling.
- Paquette, Leo A.,Sauer, Daryl R.,Cleary, Darryl G.,Kinsella, Mary A.,Blackwell, Christopher M.,Anderson, Lawrence G.
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p. 7375 - 7387
(2007/10/02)
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- Competitive Intramolecular Cycloaddition and Tandem Cycloaddition/-Sigmatropic Rearrangement Sequence of Allenyl 3-Vinyl-2-cyclohexenyl Ethers: Evidence for Switching of the Reaction Pathway by the Substituent Effects
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The base-catalyzed intramolecular cycloaddition reactions (t-BuOK, t-BuOH, 83 deg C) of variously substituted propargyl 3-vinyl-2-cyclohexenyl ethers have been investigated.The reaction proceeded smoothly via the initial isomerization to the corresponding
- Hayakawa, Kenji,Aso, Kazuyoshi,Shiro, Motoo,Kanematsu, Ken
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p. 5312 - 5320
(2007/10/02)
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