journal
MENU ▼
Read by QxMD icon Read
search

Tetrahedron Letters

journal
https://www.readbyqxmd.com/read/28163339/synthesis-and-antiviral-evaluation-of-2-2-3-3-tetrafluoro-nucleoside-analogs
#1
Ozkan Sari, Leda Bassit, Christina Gavegnano, Tamara R McBrayer, Louise McCormick, Bryan Cox, Steven J Coats, Franck Amblard, Raymond F Schinazi
Herein, we report the synthesis of novel 2',2',3',3'-tetrafluorinated nucleoside analogs along with their phosphoramidate prodrugs. A tetrafluoro ribose moiety was coupled with different Boc/benzoyl-protected nucleobases under Mitsunobu conditions. After deprotection, tetrafluorinated nucleosides 13b, 14b, 20b-22b were reacted with phenyl-(isopropoxy-L-alaninyl)-phosphorochloridate to afford corresponding monophosphate prodrugs 24b-28b. All synthesized compounds were evaluated against several DNA and RNA viruses including HIV, HBV, HCV, Ebola and Zika viruses...
February 15, 2017: Tetrahedron Letters
https://www.readbyqxmd.com/read/28066032/ochrocephalamine-a-a-new-quinolizidine-alkaloid-from-oxytropis-ochrocephala-bunge
#2
Li-Na Liu, Jian-Qiang Ran, Li-Jun Li, Yu Zhao, Masuo Goto, Susan L Morris-Natschke, Kuo-Hsiung Lee, Bao-Yu Zhao, Cheng-Jian Tan
One dimeric matrine-type alkaloid, ochrocephalamine A (1), was isolated from the poisonous plant Oxytropis ochrocephala Bunge. Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction. The insecticidal and cytotoxic activities of 1 were evaluated.
November 16, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27713589/replacement-of-the-bryostatin-a-and-b-pyran-rings-with-phenyl-rings-leads-to-loss-of-high-affinity-binding-with-pkc
#3
Mark E Petersen, Noemi Kedei, Nancy E Lewin, Peter M Blumberg, Gary E Keck
We describe a convergent synthesis of a bryostatin analogue in which the natural A- and B-ring pyrans have been replaced by phenyl rings. The new analogue exhibited PMA like behavior in cell assays, but failed to maintain high affinity binding for PKC, despite retaining an unaltered C-ring 'binding domain'.
October 19, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/28260819/synthesis-of-site-specifically-13-c-labeled-linoleic-acids
#4
Adam R Offenbacher, Hui Zhu, Judith P Klinman
Soybean lipoxygenase-1 (SLO-1) catalyzes the C-H abstraction from the reactive carbon (C-11) in linoleic acid as the first and rate-determining step in the formation of alkylhydroperoxides. While previous labeling strategies have focused on deuterium labeling to ascertain the primary and secondary kinetic isotope effects for this reaction, there is an emerging interest and need for selectively enriched (13)C isotopologues. In this report, we present synthetic strategies for site-specific (13)C labeled linoleic acid substrates...
October 12, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/28239199/synthesis-of-8-1-2-3-triazol-1-yl-7-deazapurine-nucleosides-by-azide-alkyne-click-reactions-and-direct-c-h-bond-functionalization
#5
Sam Kavoosi, Ramanjaneyulu Rayala, Brenna Walsh, Maria Barrios, Walter G Gonzalez, Jaroslava Miksovska, Logesh Mathivathanan, Raphael G Raptis, Stanislaw F Wnuk
Treatment of toyocamycin or sangivamycin with 1,3-dibromo-5,5-dimethylhydantoin in MeOH (r.t./30 min) gave 8-bromotoyocamycin and 8-bromosangivamycin in good yields. Nucleophilic aromatic substitution of 8-bromotoyocamycin with sodium azide provided novel 8-azidotoyocamycin. Strain promoted click reactions of the latter with cyclooctynes resulted in the formation of the 1,2,3-triazole products. Iodine-mediated direct C8-H bond functionalization of tubercidin with benzotriazoles in the presence of tert-butyl hydroperoxide gave the corresponding 8-benzotriazolyltubercidin derivatives...
September 28, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/28138199/rapid-microwave-accelerated-synthesis-of-1-2-4-triazolo-3-4-b-1-3-4-oxadiazoles-from-4-acylamino-1-2-4-triazoles
#6
Stesphanie L Breunig, Margaret E Olson, Daniel A Harki
1,2,4-Triazoles and 1,3,4-oxadiazoles are prevalent moieties in pharmaceutical agents, yet fused [1,2,4]-triazolo[3,4-b][1,3,4]oxadiazoles are surprisingly under-represented for both synthesis and biological application. We report a rapid, two-step synthesis of [1,2,4]-triazolo[3,4-b][1,3,4]oxadiazoles from commercial 4-amino-1,2,4-triazoles that is highlighted by a microwave accelerated intramolecular cyclization to generate the fused ring system. Our efforts to optimize reaction conditions and elucidate reaction mechanism are also described...
September 7, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/28042179/tritylation-of-alcohols-under-mild-conditions-without-using-silver-salts
#7
Shahien Shahsavari, Jinsen Chen, Travis Wigstrom, James Gooding, Alexander Gauronskas, Shiyue Fang
Secondary alcohols were conveniently tritylated under mild conditions within a short running time with tritylium trifluoroacetate generated in situ from trityl alcohols and trifluoroacetic anhydride. No expensive silver salts were needed for the reactions. Four secondary alcohols were tritylated with both mono- and dimethoxy trityl alcohols giving good to excellent isolated yields. The reaction was also tested on four nucleoside derivatives that have primary alcohols. Satisfactory results were also obtained...
August 24, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27713588/acceleration-of-metallacycle-mediated-alkyne-alkyne-cross-coupling-with-tmscl
#8
James S Cassidy, Haruki Mizoguchi, Glenn C Micalizio
Investigation of titanium-centered metallacycle-mediated cross-coupling between unsymmetrical internal alkynes has led to the discovery that TMSCl significantly accelerates the C-C bond forming event. We report a collection of results that compare the efficiency of this reaction employing Ti(Oi-Pr)4/2n-BuLi in PhMe with and without TMSCl, demonstrating in every case that the presence of TMSCl has a profound impact on efficiency. While relevant in the context of developing this fundamental bond-forming process as an entry to more complex organometallic transformations, these modified reaction conditions allow coupling processes to be run at > 10 times the concentrations previously possible [in 2...
August 24, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27546917/two-step-enzymatic-synthesis-of-6-deoxy-l-psicose
#9
Liuqing Wen, Kenneth Huang, Yuan Zheng, Junqiang Fang, Shukkoor Muhammed Kondengaden, Peng George Wang
Rare sugars offer a plethora of applications in the pharmaceutical, medicinal, and industries, as well as in synthetic chemistry. However, studies of rare sugars have been hampered by their relative scarcity. In this work, we describe a two-step strategy to efficiently and conveniently prepare 6-deoxy-L-psicose from L-rhamnose. In the first reaction step, the isomerization of L-rhamnose (6-deoxy-L-mannose) to L-rhamnulose (6-deoxy-L-fructose) catalyzed by L-rhamnose isomerase (RhaI), and the epimerization of L-rhamnulose to 6-deoxy-L-psicose catalyzed by D-tagatose 3-epimerase (DTE) were coupled with selective phosphorylation reaction by fructose kinase from human (HK), which selectively phosphorylate 6-deoxy-L-psicose at C-1 position...
August 24, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27795589/a-novel-stereoselective-8-2-double-cycloaddition-route-to-hydronaphthalene-ring-systems
#10
Weijiang Ying, Lei Zhang, Paul A Wiget, James W Herndon
Substituted hydronaphthalenes where each of the ten carbons of the two-ring system contains functionality were obtained through a tandem [8+2] cycloaddition and base-catalyzed rearrangement process using dienylfurans and electron-deficient alkynes. If the [8+2] process is conducted under solvent-free conditions the process could be conducted in a single reaction flask without isolation of the chromatographically sensitive [8+2] cycloadducts. A mechanism involving base catalysed alkene positional isomerization followed by disrotatory electrocyclic ring closure was proposed for the key reaction step that converts [8+2] cycloadducts to hydronaphthalenes...
July 6, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27818534/an-enantioselective-synthesis-of-the-c3-c21-segment-of-the-macrolide-immunosuppressive-agent-fr252921
#11
Arun K Ghosh, Samuel Rodriguez
An enantioselective synthesis of the C3-C21 segment of the novel immunosuppressant FR252921 is described. The C12 and C13 stereogenic centers were constructed by a non-aldol process utilizing optically active 4-phenylbutyrolactone. The C18 stereogenic center was installed using Braun's highly diastereoselective acetate aldol reaction. Other key steps involved Curtius rearrangement and Horner-Wadsworth-Emmons olefination reactions.
June 29, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27956752/functionalizing-the-%C3%AE-position-of-%C3%AE-diazo-%C3%AE-ketoesters
#12
Thu Q Nguyen, Maha Alqurafi, Cash Edwards, Pauline Nguyen, Jean Kim, Samuel Casco, Maricka Bennet, Christopher Chiang, Maureen Lohry, Melina Cox, Byron Meshram, Duyen Le, Eugene Kim, Snigdha Smriti, Peter Oelschlaeger, John D Buynak
Although α-diazo-β-ketoesters are synthetically versatile intermediates, methodology for introducing this functionality into complex molecules is still limited, most frequently involving a carboxylic acid precursor, which is then activated and transformed into a β-ketoester, with the diazo group being subsequently added with a diazo transfer reagent. While introducing this highly functional moiety in a convergent one step process would be ideal, such an objective is limited by the relatively few studies which address functionalization of the α-diazo-β-ketoester at the γ-position...
June 27, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27909348/rapid-cycloaddition-of-a-diazo-group-with-an-unstrained-dipolarophile
#13
Matthew R Aronoff, Brian Gold, Ronald T Raines
The cycloaddition of a diazoacetamide with ethyl 4,4,4-trifluorocrotonate proceeds with k = 0.1 M(-1)s(-1). This second-order rate constant rivals those of optimized strain-promoted azide- alkyne cycloadditions, even though the reaction does not release strain. The regioselectivity and a computational distortion/interaction analysis of the reaction energetics are consistent with the formation of an N-H…F-C hydrogen bond in the transition state and the electronic character of the trifluorocrotonate. Analogous reactions with an azidoacetamide dipole or with an acrylate or crotonate dipolarophile were much slower...
June 1, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27182092/a-mild-and-efficient-approach-to-enantioenriched-%C3%AE-hydroxyethyl-%C3%AE-%C3%AE-unsaturated-%C3%AE-lactams
#14
Seo-Jung Han, Brian M Stoltz
A straightforward approach toward enantioenriched α-substituted α,β-unsaturated δ-lactams is described. Although a considerable number of approches toward α,β-unsaturated δ-lactams have been reported, there are relatively few examples of enantioenriched α,δ-disubstituted α,β-unsaturated δ-lactams formation. The δ-stereocenter was formed by addition of allylmagnesium bromide to an N-tert-butylsulfinyl imine. The α,β-unsaturated δ-lactam was furnished by ring-closing metathesis. Although Baylis-Hillman chemistry failed on this cyclic compound, introduction of the hydroxyethyl group prior to ring-closing metathesis was successful...
May 25, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27274586/progress-in-kdo-glycoside-chemistry
#15
Paul Kosma
Glycosylation chemistry of 3-deoxy-D-manno-oct-2-ulosonic acid units has been considerably developed within the last decade. This review covers major achievements with respect to improved yields and anomeric selectivity as well as suppression of the elimination side reaction via selection of dedicated protecting groups and appropriate activation of the anomeric center.
May 18, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27175039/unusual-hydroxyl-effect-on-fulvene-endoperoxide-decompositions
#16
Ihsan Erden, John Basada, Daniela Poli, Gabriel Cabrera, Fupei Xu, Scott Gronert
The thermal decomposition of fulvene endoperoxides ordinarily proceeds via an allene oxide intermediate affording oxepin-2(3H)-one derivatives. We have now uncovered new, unusual pathways in these decompositions where the presence of a hydroxyl group on the alkyl or aryl attached to the fulvene exocyclic double bond has a profound effect on the fate of the reactive intermediates derived from the unstable endoperoxides. Computational work supports the proposed mechanistic pathways.
May 18, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27152055/an-alternative-synthesis-and-x-ray-crystallographic-confirmation-of-stepholidine
#17
Satishkumar V Gadhiya, Chunhua Hu, Wayne W Harding
A formal enantioselective synthesis of (-)-stepholidine that provides an alternative preparation of key lactone intermediate 2 is described. The stereostructure of (-)-stepholidine prepared via this method was confirmed by x-ray diffraction.
May 11, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27152054/c-o-bond-formation-in-a-microfluidic-reactor-high-yield-snar-substitution-of-heteroaryl-chlorides
#18
Mohammad Parvez Alam, Barbara Jagodzinska, Jesus Campagna, Patricia Spilman, Varghese John
This study describes our development of a novel and efficient procedure for C-O bond formation under mild conditions, for coupling heteroaryl chlorides with phenols or primary aliphatic alcohols. We utilized a continuous-flow microfluidic reactor for C-O bond formation in electron-deficient pyrimidines and pyridines in a much more facile manner with a cleaner reaction profile, high yield, quick scalability and without the need for the transition metal catalyst. This approach can be of general utility to make C-O bond containing intermediates of industrial importance in a continuous and safe manner...
May 11, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27182091/optimized-synthesis-of-a-pentafluoro-gem-diol-and-conversion-to-a-cf2br-glucopyranose-through-trifluoroacetate-release-and-halogenation
#19
Robert A Hazlitt, Jinu P John, Que-Lynn Tran, David A Colby
Pentafluoro-gem-diols are substrates that enable the synthesis of valuable difluoromethylene-containing organic molecules through the release of trifluoroacetate. Currently, only one synthetic strategy is available to assemble these important precursors. Herein, two new synthetic strategies to a complex pentafluoro-gem-diol are compared to the existing route, and an improved synthetic route has completed. Moreover, the first synthesis of a CF2Br-glucopyranose was finished by a tandem trifluoroacetate-release halogenation/cyclization protocol...
April 27, 2016: Tetrahedron Letters
https://www.readbyqxmd.com/read/27110042/convenient-synthesis-of-phosphonohydrazines-from-arylamines
#20
Greggory T Kent, Daniel J Blackburn, Joseph R Gonzalez, Megan L Mayer, Weiming Wu
Phosphonohydrazines were prepared in good yield from corresponding arylamines by a one-pot reaction through diazotization with an organic nitrite and treatment with a trialkyl phosphite. The trialkyl phosphite is postulated to function as a nucleophile as well as a reducing agent.
April 11, 2016: Tetrahedron Letters
journal
journal
25506
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"