- Stereospecific deuteration of 2-deoxyerythrose 4-phosphate using 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase
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Racemic 2-deoxyerythrose 4-phosphate was synthesized and one enantiomer of this compound was found to be a substrate for Escherichia coli 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, the first enzyme of the shikimate pathway. When the reaction was carried out in deuterium oxide, an enzyme-catalyzed regio- and stereoselective incorporation of deuterium into the product was observed.
- Williamson, Rachel M.,Pietersma, Amy L.,Jameson, Geoffrey B.,Parker, Emily J.
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Read Online
- The development of β-selective glycosylation reactions with benzyl substituted 2-deoxy-1,4-dithio-D-erythro-pentofuranosides: enabling practical multi-gram syntheses of 4'-Thio-2'-deoxycytidine (T-dCyd) and 5-aza-4’-thio-2’-deoxycytidine (aza-T-dCyd) to s
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The lack of effective methods to perform direct β-selective glycosylation reactions with 2-deoxy-1,4-dithio-D-erythro-pentofuranosides has long been a significant stumbling block for the multi-gram synthesis of 4’-thio-2’-deoxy nucleosides. In addition, p
- Wishka, Donn G.,Lopez, Omar D.,Rudchenko, Vladimir F.,Huang, Guangfei,Bahde, Robert,Kumar, Vineet,Denysenko, Sergiy M.,Zhang, Lianhao,Zhang, Mianji,Teicher, Beverly A.,Morris, Joel
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Read Online
- STEREOSELECTIVE SYNTHESIS AND PROCESS FOR THE MANUFACTURING OF 2'-DEOXYNUCLEOSIDES
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Methods for stereoselective synthesis and manufacturing of 2'-deoxynucleosides, such as 2'-ribonucleosides, are disclosed. In some embodiments, the 2'-deoxynucleoside is a β-anomer of 2'-deoxynucleoside having a 3' a hydroxyl, 4' β hydroxymethyl configuration. Nonlimiting examples of compounds prepared by the disclosed methods include 4'-thio-2'-deoxycytidine (T-dCyd) and 5-aza-4'-thio-2'-deoxycytidine (5-aza-T-dCyd; aza-T-dCyd; aza-T-dC).
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Page/Page column 17
(2019/08/26)
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- New strategy for the synthesis of ladybird beetle azaphenalene alkaloids using a combination of allylboration and intramolecular metathesis. Total synthesis of (±)-Hippocasine and (±)-epi-Hippodamine
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A new strategy for assembly a tricyclic skeleton of ladybirds azaphenalene alkaloids (coccinellides) was developed based on the combination of allylboration reaction and intramolecular metathesis. The first key step is the 1,2-organolithiation of 4-picoline with (4,4-dieth-oxybutyl)lithium with subsequent reductive allylation with triallylborane leading to trans-2-allyl-6-(4,4-diethoxybutyl)-4-methyl-1,2,3,6-tetrahydropyridine. The 4,4-diethoxybutyl substituent was further converted to 4-acetoxy-5-hexenyl in four steps, then, the product obtained was involved in the second key step, the intramolecular allylic amination upon treatment with a [Pd] or an [Ir] catalyst giving diastereomeric bicyclic terminal dienes (μ1: 1), which were separated by chromatography. The stereochemistry of one of the dienes is the same as that in alkaloid Hippocasine. The third key step (the intramolecular metathesis reaction) includes the final assembly of the azaphenalene system. The tricyclic derivative obtained contains two differently substituted C=C bonds, selective hydrogenation of one of which (Pd/C) leads to (±)-Hippocasine, whereas exhaustive hydrogenation gives (±)-epi-Hippodamine.
- Kuznetsov,Lyubimov,Godovikov,Bubnov
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p. 529 - 537
(2015/02/05)
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- Direct stereospecific amination of alkyl and aryl pinacol boronates
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The direct amination of alkyl and aryl pinacol boronates is accomplished with lithiated methoxyamine. This reaction directly provides aliphatic and aromatic amines, stereospecifically, and without preactivation of the boronate substrate.
- Mlynarski, Scott N.,Karns, Alexander S.,Morken, James P.
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supporting information
p. 16449 - 16451,3
(2020/09/15)
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- Palladium-catalyzed dimerization of vinyl ethers to acetals
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(α-Diimine)PdCl+ species catalytically dimerize alkyl and silyl vinyl ethers to β,γ-unsaturated CH2=CHCH 2CH(OR)2 acetals, and they cyclize divinyl ethers to analogous cyclic acetals. A plausible mechanism comprises in situ generation of an active PdOR alkoxide species, double vinyl ether insertion to generate Pd{CH2CH(OR)CH2CH(OR)2} species, and β-OR elimination to generate the acetal product. In the presence of vinyl ethers, (α-diimine)PdCl+ species can be used to initiate ethylene polymerization.
- Chen, Changle,Jordan, Richard F.
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supporting information; experimental part
p. 10254 - 10255
(2010/09/06)
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- Enantioselective synthesis of structurally intricate and complementary polyoxygenated building blocks of spongistatin 1 (altohyrtin a)
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Enantioselective approaches to the construction of four complex building blocks of the structurally intricate marine macrolide known as spongistatin 1 are presented. The first phase of the synthetic effort relies on a practical approach to a desymmetrized, enantiomerically pure spiroketal ring system incorporating rings A and B. Concurrently, the C17-C28 subunit, which houses one-fifth of the stereogenic centers of the target in the form of rings C and D, was assembled via a composite of stereocontrolled aldol condensations. Once arrival at the entire C1-C28 sector had been realized, routes were devised to provide two additional highly functionalized sectors consisting of C29-C44 and C38-C51. A series of subsequent transformations including cyclization of the E ring and hydroboration to afford the B-alkyl intermediate for the key Suzuki coupling to append the side chain took advantage of efficient stereocontrol. Ultimately, complete assembly and functionalization of the western EF sector of spongistatin was thwarted by an inoperative Suzuki coupling step intended to join the side chain to the C29-C44 sector, and later because of complications due to protecting groups, which precluded the complete elaboration of the late stage C29-C51 intermediate.
- Braun, Alain,Cho, Ii Hwan,Ciblat, Stephane,Clyne, Dean,Forgione, Pat,Hart, Amy C.,Huang, Guoxiang,Kim, Jungchul,Modolo, Isabelle,Paquette, Leo A.,Peng, Xiaowen,Pichlmair, Stefan,Stewart, Catherine A.,Wang, Jizhou,Zuev, Dmitry
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scheme or table
p. 651 - 769
(2010/02/27)
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- First preparation of 5-allyl-1,3-oxazolidine-2-thione (napoleiferin), a natural homolog of 5-vinyl-1,3-oxazolidine-2-thione (goitrin)
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The preparation of 5-allyl-1,3-oxazolidine-2-thione (napoleiferin) 5 via a practical synthesis of but-3-enal 2 and the key intermediate 1-aminopent- 4-en-2-ol 4 is described for the first time.
- Latxague,Gardrat
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p. 1627 - 1637
(2007/10/03)
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- Synthesis of carba-strigol analogues
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Carba analogues 1, 14, 15 and 16 of Strigol were synthesised in which the vinyl ether oxygen is replaced by methylene.Compound 1 was prepared by the Wittig reaction of ylid 2 with aldehyde 3.Compounds 14, 15, and 16, for which this approach failed, were p
- Kishimba, M. A.,Zwanenburg, B.
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- Substitution of the acetoxy groups of dialkoxymethylacetates by organometallic reagents: a route to allyl-, propargyl-, homoallyl-, homopropargyl- and α-stannylacetals
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The substitution of the acetoxy groups of dialkoxymethylacetates by organometallic reagents has been examined in a search for new methods of preparing functional acetals.The efficiency of the substitution of the acetoxy group is highly dependent on the nature of the organometallic reagents: soft nucleophiles with strong electrophilic assistance by the counterion are the best reagents.Allyl-, propargyl-, homoallyl-, homopropargyl- and α-stannylacetals have been made by this route, in which dialkoxymethylacetates often function as useful substitutes for dialkylphenylorthoformates.
- Beaudet, Isabelle,Duchene, Alain,Parrain, Jean-Luc,Quintard, Jean-Paul
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p. 201 - 212
(2007/10/02)
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- New strategies for the synthesis of vitamin D metabolites via Pd-catalyzed reactions
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The invention of new palladium-catalyzed reactions offers new insights into synthetic strategies directed toward the vitamin D system. The palladium-catalyzed cycloisomerization of 1,6- and 1,7-enynes to dialkylidenecycloalkanes permits a lynchpin approach to the A ring of vitamin Ds. Using the thioacetal of formaldehyde, the proper subunits containing the olefin and the acetylene were attached. Pd(2+) effected cycloisomerization to an A ring subunit. A more effective strategy evolved from the evolution of a Pd-catalyzed alkylative cyclization of enynes. Whereas prior work established the feasibility of this process for 1,6-enynes, model studies reported herein demonstrate the feasibility of its extension to 1,7-enynes. This reaction permits the creation of a new concept for vitamin D synthesis wherein A ring formation is concomitant with its attachment to an appropriate CD fragment. An asymmetric synthesis of the requistite 1,7-enyne required six steps. Bromomethylenation of Grundmann's ketone and its side chain hydroxylated derivative proceeded with excellent geometrical selectivity (>30:1) using the Wittig reaction. A Pd catalyst generated from (dba)3Pd2·CHCl3 and triphenylphosphine stitched together these two units in a single step resulting in syntheses of alphacalcidiol and calcitriol.
- Trost, Barry M.,Dumas, Jacques,Villa, Marco
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p. 9836 - 9845
(2007/10/02)
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- Formylation of Allylsilanes: A Synthesis of β,γ-Unsaturated Aldehyde Acetals
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3-Alkenal acetals are synthesized from allylsilanes and orthoformates in the presence of Lewis acids.
- Cambanis, Anton,Baeuml, Englbert,Mayr, Herbert
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p. 128 - 129
(2007/10/02)
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- Ring Fragmentations of 2-Alkenyl- and 2-Benzyl-1,3-dithiolanes Induced by Bases. A Novel Method for the Preparation of 1,1-Bisalkylthio- or 1-Alkylthio-alk-1-enes and -alka-1,3-dienes
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The reaction of 2-alkenyl- and 2-benzyl-1,3-dithiolanes with several bases and successive alkylation with alkyl halides has been investigated.In the reaction of 2-alk-1-enyl-1,3-dithiolanes with organolithium reagents and alkyl halides, deprotonation at C
- Oida, Tatsuo,Tanimoto, Shigeo,Terao, Hiromu,Okano, Masaya
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p. 1715 - 1726
(2007/10/02)
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- An Efficient Synthesis of α,β-Unsaturated Aldehydes by a Four-Carbon Unit Extension of Grignard Reagents
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Copper-catalyzed addition of organomagnesium halides to 2-(2,2-diethoxy-ethyl)oxirane (1) affords aldol acetals 2 which upon acid treatment undergo hydrolysis and dehydration to give α,β-unsaturated aldehydes 7 with high yields.
- Cloux, Roland,Schlosser, Manfred
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p. 1470 - 1474
(2007/10/02)
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- CHEMISTRY OF ENOLIC ETHERS. LI. SYNTHESIS AND INVESTIGATION OF THE STEREOCHEMISTRY OF THE ACETALS OF β,γ-UNSATURATED δ-HYDROXYALDEHYDES BY NMR SPECTROSCOPY
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A new accessible method is proposed for the synthesis of the acetals of ethynylacetaldehyde by the addition of bromine to the acetals of vinylacetaldehyde and subsequent dehydrobromination of the obtained 1,1-dialkoxy-3,4-dibromobutanes with sodium amide.The Iotich condensation of the ethynylacetaldehyde acetals with paraform and acetaldehyde was investigated.A stereoselective synthesis of the individual cis and trans isomers of β,γ-unsaturated δ-hydroxyaldehydes was realized from the obtained acetylenic alcohols.
- Raifel'd, Yu. E.,Kusikova, I. P.,Zil'berg, L. L.,Arshava, B. M.,Limanova, O. V.,Makin, S. M.
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p. 1425 - 1429
(2007/10/02)
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- Action d'organometalliques sur les dialkylphenylorthoformiates. Preparation facile d'acetals
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The reaction of dialkylphenylorthoformiates with organometallic compounds proceeds with a good yield, at room temperature, giving the corresponding dialkylacetals ; it allows an easy preparation of acetals which are otherwise difficult to prepare.
- Barbot, Francis,Poncini, Laurence,Randrianoelina, Benjamin,Miginiac, Philippe
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p. 4016 - 4035
(2007/10/02)
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