- Total synthesis and stereochemical assignment of (-)-ushikulide A
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We report the determination of the full stereostructure of (-)-ushikulide A (1), a spiroketal containing macrolide by total synthesis. Ushikulide A (1) was isolated from a culture broth of Streptomyces sp. IUK-102 and exhibits potent immunosuppressant activity (IC50 = 70 nM). To embark upon an ushikulide A synthesis, a tentative assignment was made based on analogy to cytovaricin (2), a related macrolide isolated from a culture of Streptomyces diastatochromogenes whose full structure was previously established via synthesis and X-ray crystallography. This report delineates studies on several key steps, namely a direct aldol reaction catalyzed by the dinuclear zinc ProPhenol complex, a metal catalyzed spiroketalization, as well as application of an unprecedented asymmetric alkynylation of a simple saturated aldehyde with methyl propiolate to prepare the nucleophilic partner for a Marshall-Tamaru propargylation. These studies culminated in the first total synthesis and stereochemical assignment of (-)-ushikulide A and significantly extended the scope of the above-mentioned methodologies.
- Trost, Barry M.,O'Boyle, Brendan M.,Hund, Daniel
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supporting information; experimental part
p. 15061 - 15074
(2010/01/30)
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- Complete control of regioselectivity in the intramolecular [2 + 2] photocycloaddition of 2-alkenyl-3(2H)-furanones by the length of the side chain
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The 2-(ω-alkenyl)-substituted 2-methyl-3(2H)-furanones 2a and 2b were prepared from biacetyl (3) in four reaction steps and in overall yields of 20% and 21%, respectively. They underwent a clean intramolecular [2 + 2] photocycloaddition upon irradiation a
- Bach, Thorsten,Kemmler, Michael,Herdtweck, Eberhardt
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p. 1994 - 1997
(2007/10/03)
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- Novel reactions of indium reagents with 1,2-diones: A facile synthesis of α-hydroxy ketones
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Indium mediated reactions of allyl, cinnamyl, propargyl and benzyl bromides, ethyl bromoacetate and ethyl-4-bromocrotonate with 1,2-diones, in the presence of sodium iodide, occur efficiently to afford α-hydroxy keto compounds in excellent yields.
- Nair, Vijay,Jayan,Ros, Sindu
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p. 9453 - 9459
(2007/10/03)
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- Indium mediated Barbier reactions of 1,2-diones: A facile synthesis of α-hydroxy ketones
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Indium mediated allylation and cinnamylation of 1,2-diones with the corresponding bromides in the presence of sodium iodide produce α-carbonyl homoallylic alcohols in excellent yields. (C) 2000 Elsevier Science Ltd.
- Nair, Vijay,Jayan
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p. 1091 - 1094
(2007/10/03)
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- Allylstannation of α-, β-and γ-diketones mediated by allylbutyltin halides: Bu2(CH2=CHCH2)SnCl and Bu(CH2=CHCH2) SnCl2
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Butane-2,3-(1a), pentane-2,4-(1b) and hexane-2,5-dione (1c) react with Bu2(CH2=CHCH2)SnCl in the presence of water to give monoallylated keto-ols (2a, 2b) and/or diallylated diols (3a, 3b, 3c), this depending upon the employed molar ratio [diketone]/[allyltin chloride]. Bu(CH2=CHCH2)SnCl2 reacts with neat 1c in a one-pot synthesis to give mixtures of heterocyclic compounds: 2,5-diallyl-2,5-dimethyltetrahydrofuran (4), and 3-chloro-1,5-dimethyl-8-oxabicyclo [3,2,1] octane (5). Compound 4 is also obtained in high yield from the corresponding diol 3c by cyclodehydration promoted by RSnCl3 (R = Me and Bu).
- Marton, Daniele,Stivanello, Diego,Tagliavini, Giuseppe
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- Rearrangement of α-hydroxy imines to α-amino ketones: Mechanistic aspects and synthetic applications
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In refluxing diglyme, rearrangement of α-hydroxy imines bearing diversely substituted allyl groups or a 3-trimethylsilylpropargyl group on the α-carbon to the nitrogen afforded in good yields α-amino ketones. Migration of allyl or 3-trimethylsilylallyl groups occurred without allylic transposition in contrast to be 1-methylallyl group. In the 3 cases studied, the rearrangement of enantioenriched α-hydroxy imines took place with complete 1,2-chirality transfer. The rearrangement was applied to the preparation of (+)-1-benzyl-1-azaspiro[5.5]undecan-7-one, a precursor in the synthesis of (-)-perhydrohistrionicotoxin.
- Compain,Gore,Vatele
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p. 6647 - 6664
(2007/10/03)
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- THERMAL REARRANGEMENT OF α-HYDROXY IMINES WITH AN α-ALLYL OR AN α-PROPARGYL SUBSTITUENT
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In refluxing diglyme, the title α-hydroxy imines 7 and 8 rearrange cleanly to amino ketones 9 and 10 substituted on the carbon α to nitrogen by an allyl or a propargyl group.In the case of α-hydroxy imine 9, the migration of the allyl group occurs with an allylic transposition.
- Vatele, Jean-Michel,Dumas, Daniel,Gore, Jacques
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p. 2277 - 2280
(2007/10/02)
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