- De Novo Asymmetric Synthesis of Phoracantholide J
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A de novo asymmetric total synthesis of the macrolide natural product (S)-phoracantholide J has been achieved in 10 steps from the commodity chemicals (1-pentyne, ethyl acrylate, acetaldehyde, and hydrogen). The asymmetry of the route was introduced by a Noyori reduction of a 3-yn-2-one, which makes the route equally amenable to the synthesis of either enantiomer. In addition, this route relies upon an alkyne zipper, a hydroalkynylation, and a macrolactonization to complete the synthesis.
- Avocetien, Kenneth F.,Li, Jiazhen J.,Liu, Xiaofan,Wang, Yanping,Xing, Yalan,O'Doherty, George A.
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- A short enantioselective synthesis of (R)-nostrenol
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The catalytic asymmetric synthesis of (-)-(R)-nostrenol is described in five steps starting from commercially available 1-pentyne. The key steps are a Noyori catalytic and asymmetric hydrogen transfer and a Cp2TiCl 2 catalyzed hydroalumination.
- Petry, Nicolas,Parenty, Arnaud,Campagne, Jean-Marc
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- Synthesis of the C7-C24 fragment of (-)-Macrolactin F
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An enantioselective and convergent synthesis of the C7-C24 fragment of Macrolactin F was achieved from four main fragments. A hydrotelluration/transmetalation sequence was used to install the E,Z diene present in the molecule, while a hydrozirconation/transmetalation sequence was used to connect two advanced intermediates.
- Oliveira, Roberta A.,Oliveira, Juliana M.,Rahmeier, Luis H.S.,Comasseto, Joao V.,Marino, Joseph P.,Menezes, Paulo H.
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- Routine use of natural abundance deuterium NMR in a polypeptidic chiral oriented solvent for the determination of the enantiomeric composition of chiral building blocks.
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[reaction: see text] Natural abundance deuterium 2D NMR spectroscopy in chiral liquid crystal was successfully used to efficiently analyze the enantiomeric composition of organic chiral building blocks involved in the syntheses of natural and synthetic bioactive products. The results reported here emphasize the high potential of this analytical strategy and prove its applicability for routinely determining enantiomeric excesses.
- Parenty, Arnaud,Campagne, Jean-Marc,Aroulanda, Christie,Lesot, Philippe
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- Easy preparation of 1,4,5-trisubstituted 5-(2-alkoxy-1,2-dioxoethyl)-1,2,3- triazoles by chemoselective trapping of copper(I)-carbon bond with alkoxalyl chloride
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We found that alkoxalyl chloride (ClCOCO2R) did not carry out an acylation on 1-copper(I) alkyne in solvent without additives, but chemoselectively on 5-copper(I) 1,2,3-triazole (an intermediate in cycloaddition of 1-copper(I) alkyne and azide). Thus, a one-pot preparation of 1,4,5-trisubstituted 5-(2-alkoxy-1,2-dioxoethyl)-1,2,3-triazole was achieved by simply stirring the mixture of 1-copper(I) alkyne, azide, and alkoxalyl chloride at room temperature for 4 h.
- Wang, Bo,Ahmed, Muhammad Naeem,Zhang, Jianlan,Chen, Wenwen,Wang, Xinyan,Hu, Yuefei
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p. 6097 - 6100
(2013/10/22)
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- Transition-metal-catalyzed synthesis of aspergillide B: An alkyne addition strategy
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A catalytic enantioselective formal total synthesis of aspergillide B is reported. This linchpin synthesis was enabled by the development of new conditions for Zn-ProPhenol catalyzed asymmetric alkyne addition. This reaction was used in conjunction with ruthenium-catalyzed trans-hydrosilylation to affect the rapid construction of a late-stage synthetic intermediate of aspergillide B to complete a formal synthesis of aspergillide B in a highly efficient manner.
- Trost, Barry M.,Bartlett, Mark J.
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supporting information; experimental part
p. 1322 - 1325
(2012/04/23)
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- Stereoselective Synthesis of Highly Functionalized Trisubstituted Olefins via the Aldol Reaction of Allenoxyborinates with Carbonyl Compounds
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Allenoxyborinates, generated via the reaction of dicyclohexylborane with α,β-acetylenic ketones, react in situ with excess starting ketone to afford stereodefined, functionalized, trisubstituted olefins in good yields. The allenoxyborinates, (RCH=C=C(R′)OB(c-C6H11)2, can also be trapped by aldehydes and ketones when R′ is a tert-butyl group.
- Yu, Su,Li, Nan-Sheng,Kabalka, George W.
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p. 5822 - 5825
(2007/10/03)
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- The Autoxidation of Hept-3-yne
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In the reaction mixtures of the oxidation of hept-3-yne with molecular oxygen as products of the attack on the C-C triple bond heptane-3,4-dione, propionic and butyric acids and a very small amount of 2-ethylvaleric acid were found.Hept-2-en-4-one and hept-3-en-5-one were probably present, but could not be identified unambiguously.As in the case of the isomeric octynes the main primary reaction products were the hydroperoxides formed by attack on the C-H bonds in α-position to the CC triple bond.
- Brose, Th.,Pritzkow, W.,Sebald, F.,Voerckel, V.
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p. 951 - 956
(2007/10/02)
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- Cyclopentenone Derivatives, IX. - Enantioselective Routes to Brefeldin-A
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By combining stereoselective Michael additions to substituted cyclopentenones with a stereospecific reduction of the C4 ketone, which is controlled by the C15 configuration, an enantioselective route to (-)-brefeldin-A is developed, starting with the easily available chiral carbinol 11.A second technique makes use of chirality transfer in Michael additions to chiral 4-acetoxy-2-cyclopenten-1-one.
- Marx, Karl-Heinz,Raddatz, Peter,Winterfeldt, Ekkehard
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p. 474 - 482
(2007/10/02)
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- Stereoselectivity in the Addition of Organocuprates to β-Alkylthio α,β-Enones
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Factors affecting the direction and degree of stereoselectivity in the conjugate addition-elimination reaction of organocuprates with β-alkylthio α,β-enones are described.
- Dieter, R. Karl,Silks, Louis A.
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p. 2786 - 2788
(2007/10/02)
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- Photooxidation of Strained Olefins. 4. Cyclopropenes
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The photosensitized oxidation of cyclopropenes 5a-c proceeds rapidly, producing a plethora of products whose formation can be understood in terms of secondary rearrangements of initially formed products hydroperoxide 24 and epoxide 29.However, the reaction does not involve singlet oxygen but is rather a free-radical process.
- Frimer, Aryeh A.,Antebi, Abraham
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p. 2334 - 2340
(2007/10/02)
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