- RAPID SYNTHESIS OF 2',3'-DIDEOXYCYTIDINE (ddC) FROM A SIMPLE ACHIRAL PRECURSOR
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The antiviral nucleoside analogue, 2',3'-dideoxycytidine (ddC) 1, has been synthesized in nine steps and good overall yield from crotonaldehyde 2 via the chiral epoxy alcohol 4 prepared by a Sharpless oxidation.
- Jung, Michael E.,Castro, Claire,Gardiner, John M.
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- Stereoselective Addition of Nucleophiles on α-Trialkylsilyl-β,γ-Unsaturated Aldehydes
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Palladium(0)-catalyzed rearrangement of silicon substituted vinyloxiranes is depending on the size of the trialkylsilyl groups.Addition of organolithium or Grignard reagents on α-trialkylsilyl-β,γ-unsaturated aldehydes furnished the corresponding alcohols
- Bideau, Franck Le,Gilloir, Fabienne,Nilsson, Ylva,Aubert, Corinne,Malacria, Max
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- Influence of the acetylenic substituent on the intramolecular carbolithiation of alkynes
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The intramolecular carbolithiation of a series of propargylic ethers has been performed to evaluate the influence of the terminal substituent on the efficiency and the stereochemical outcome of the cyclization. Our results show that only 5-exo-dig cyclizations are observed, and dihydrobenzofurans are obtained exclusively. Depending on the nature of the terminal substituent, two cases can be considered. If the terminal substituent carried by the acetylenic carbon atom is itself a carbon atom, the cyclization can occur provided the terminal propargylic position bears a coordinating element and is at least disubstituted. When the cyclization occurs, it follows an anti-carbolithiation pathway and thus leads to the E isomer of the exocyclic double bond. Only in one case (Ph) was a mixture of the E and Z isomers of the resulting olefin recovered. The cyclization can also take place if the alkyne is directly substituted by S or Si, provided the cyclization conditions are tuned. In the case of the trimethylsilyl substituent, a syn-carbolithiation was observed. If the double bond is recovered, in most cases, in the exocyclic position, the products can aromatize directly for SPh-substituted substrate 24. Furthermore, in the two latter cases, when alkylation of the vinyllithium intermediate is performed, isomerization of the double bond seems instantaneous. Copyright
- Girard, Anne-Lise,Lhermet, Rudy,Fressigne, Catherine,Durandetti, Muriel,Maddaluno, Jacques
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experimental part
p. 2895 - 2905
(2012/06/29)
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- A synthesis of tamiflu by using a barium-catalyzed asymmetric diels-alder-type reaction
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(Chemical Equation Presented) In pursuit of a better route: A new catalytic asymmetric synthesis of Tamiflu was developed. The key transformation was an asymmetric Diels-Alder-type reaction of 1 and 2 catalyzed by a barium/F 2-FujiCAPO complex in the presence of a CsF co-catalyst to construct the core of Tamiflu (see scheme; TMS=trimethylsilyl). The product was converted into Tamiflu in 11 steps on a gram scale.
- Yamatsugu, Kenzo,Yin, Liang,Kamijo, Shin,Kimura, Yasuaki,Kanai, Motomu,Shibasaki, Masakatsu
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supporting information; experimental part
p. 1070 - 1076
(2009/06/20)
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- Stereocontrolled synthesis of α-trialkylsilyl-β,γ-unsaturated aldehydes via palladium (0) catalysis synthetic usefulness
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The reaction of silicon substituted vinyloxiranes in the presence of catalytic amount of palladium (0) catalyst affords the title compounds. This new reaction proceeds smoothly, under very mild conditions and with complete chirality transfer. One-pot addition of selected organometallic nucleophiles to these aldehydes at very low temperature led to a highly selective preparation of the corresponding alcohols in very good yields. Influence of substituents on the silicon atom and of the ligands of palladium have been studied.
- Le Bideau,Gilloir,Nilsson,Aubert,Malacria
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p. 7487 - 7510
(2007/10/03)
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- Synthetic Approaches to 3'-Azido-3'-deoxythymidine and Other Modified Nucleosides
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An efficient stereospecific total synthesis of AZT (nine steps from crotonaldehyde) is reported in which the chirality is introduced via Sharpless epoxidation and therefore intermediates for the synthesis of both D- and L-AZT are easily produced.
- Jung, Michael E.,Gardiner, John M.
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p. 2614 - 2615
(2007/10/02)
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- AN EFFICIENT SYMTHESIS OF SILYL ENOL ETHERS FROM α,β-UNSATURATED ALDEHYDES AND KETONES
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α,β-Unsaturated aldehydes and ketones when reacted with NaBr-Me3SiCl-Et3N in DMF at ambient temperature, yield silyl dienol ethers in high yields.
- Iqbal, Javed,Khan, M. Amin
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p. 515 - 522
(2007/10/02)
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- CHEMISTRY OF ENOL ETHERS. LVIII. REACTION OF GLUTACONIC ALDEHYDE AND ITS ALKYL DERIVATIVES WITH 1-TRIMETHYLSILYLOXY-1,3-DIENES
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The action of ethyl orthoformate on monoacetals of glutaconic aldehyde and its alkyl derivatives yielded the diacetals of the corresponding glutaconic aldehydes.The condensation of these compounds with 1-trimethylsilyloxy-1,3-dienes was studied.This condensation proceeds regioselectively, involving only the α,β-unsaturated acetal group, and gives 5,9,9-trialkoxy-2,6-nonadienals.
- Makin, S. M.,Kruglikova, R. I.,Popova, T. P.
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p. 1001 - 1003
(2007/10/02)
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- O-SILYLATED DIENOLATES IN ORGANIC SYNTHESIS: γ-SELECTIVE ALKYLATION OF UNSATURATED CARBONYL COMPOUNDS BY 1,3-DITHIENIUM FLUOROBORATE
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The alkylation of O-silylated dienolates of unsaturated aldehydes, ketones, and esters with 1,3-dithienium fluoroborate shows useful γ-selectivity.The γ-products are selectively protected 1,5-dicarbonyl compounds.
- Paterson, Ian,Price, Lee G.
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p. 2833 - 2836
(2007/10/02)
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