journal
https://read.qxmd.com/read/35495552/regioselective-alkylation-of-2-4-dihydroxybenzyaldehydes-and-2-4-dihydroxyacetophenones
#21
JOURNAL ARTICLE
Aziza Frank, Negar Hamidi, Fengtian Xue
We report a cesium bicarbonate-mediated alkylation of 2,4-dihydroxybenzyaldehyde and 2,4-dihydroxyacetophenone to generate 4-alkylated products in acetonitrile at 80 °C with excellent regioselectivity, up to 95% isolated yields, and broad substrate scope.
April 13, 2022: Tetrahedron Letters
https://read.qxmd.com/read/35935920/synthesis-of-a-boron-containing-amidoxime-reagent-and-its-application-to-synthesize-functionalized-oxadiazole-and-quinazolinone-derivatives
#22
JOURNAL ARTICLE
Bhaskar C Das, Nitesh K Nandwana, Devi P Ojha, Sasmita Das, Todd Evans
Herein, we report the design, synthesis and application of a borylated amidoxime reagent for the direct synthesis of functionalized oxadiazole and quinazolinone derivatives. This reagent exhibits broad synthetic utility to obtain a variety of biologically relevant drug-like molecules. It can be easily prepared at large scale from relatively inexpensive reagents, and can undergo facile transformations to obtain target compounds. The developed amidoxime reagent was synthesized from 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile and hydroxyl amine hydrochloride using N,N -diisopropylethylamine as a base in ethanol under reflux conditions...
March 2, 2022: Tetrahedron Letters
https://read.qxmd.com/read/35140452/synthetic-studies-towards-isomeric-pyrazolopyrimidines-as-potential-atp-synthesis-inhibitors-of-mycobacterium-tuberculosis-structural-correction-of-reported-n-6-2-dimethylamino-ethoxy-5-fluoropyridin-3-yl-2-4-fluorophenyl-5-trifluoromethyl-pyrazolo-1-5-%C3%AE-pyrimidin
#23
JOURNAL ARTICLE
Peter J Choi, Guo-Liang Lu, Hamish S Sutherland, Anna C Giddens, Scott G Franzblau, Christopher B Cooper, William A Denny, Brian D Palmer
During our studies into preparing analogues of pyrazolopyrimidine as ATP synthesis inhibitors of Mycobacterium tuberculosis , a regiospecific condensation reaction between ethyl 4,4,4-trifluoroacetoacetate and 3-(4-fluorophenyl)-1 H -pyrazol-5-amine was observed which was dependent on the specific reaction conditions employed. This work identifies optimized reaction conditions to access either the pyrazolo[3,4- β ]pyridine or the pyrazolo[1,5- α ]pyrimidine scaffold. This has led to the structural confirmation of the previously reported pyrazolopyrimidine 17b which was reported as pyrazolo[1,5- α ]pyrimidine structure 2 which was corrected to pyrazolo[3,4- β ]-pyrimidine 19 ...
February 2, 2022: Tetrahedron Letters
https://read.qxmd.com/read/35719215/stereoselective-desymmetrizations-of-dinitriles-to-synthesize-lactones
#24
JOURNAL ARTICLE
Amber M Kelley, Joshua A Frost, Tylisha M Baber, Kala C Youngblood, Emiri Michishita, Schuyler A Bain, T Caleb Lykins, Kimberly S Petersen
Nitriles are important organic functional groups, allowing for installation of nitrogen in organic synthesis. The Pinner reaction transforms nitriles into esters via the imidate group, but in general has previously necessitated harsh acid conditions. This work builds on the utility of the Pinner reaction through a stereoselective desymmetrization of dinitriles to form γ- and δ-lactones in good yields and diastereoselectivites.
January 5, 2022: Tetrahedron Letters
https://read.qxmd.com/read/34955565/interception-of-1-2-cyclohexadiene-with-tempo-radical
#25
JOURNAL ARTICLE
Matthew S McVeigh, Neil K Garg
Transient strained cyclic intermediates, such as strained cyclic allenes, are useful building blocks for the synthesis of structurally and stereochemically complex scaffolds. Trappings of strained cyclic allenes are thought to occur primarily through either two or one electron processes. Regarding the latter, diradical intermediates have been invoked in (2 + 2) cycloadditions and (3 + 2) nitrone cycloadditions. The present study questions if a monoradical pathway could exist for strained cyclic allene reactivity, as examined in the reaction of 1,2-cyclohexadiene and TEMPO radical...
December 21, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34908617/total-synthesis-of-remdesivir
#26
JOURNAL ARTICLE
Kishore Kumar Palli, Palash Ghosh, Shiva Krishna Avula, B Sridhara Shanmukha Rao, Amol D Patil, Subhash Ghosh, Gangarajula Sudhakar, Chada Raji Reddy, Prathama S Mainkar, Srivari Chandrasekhar
Remdesivir, the first drug approved by the FDA to treat COVID-19, is in high demand for patients infected with the SARS-CoV-2 virus. Herein, we report a facile approach minimizing the protecting group manipulations to afford remdesivir in good overall yield.
December 9, 2021: Tetrahedron Letters
https://read.qxmd.com/read/35153339/mercapto-functionalized-polyhedral-oligomeric-silsesquioxane-as-a-soluble-support-for-the-synthesis-of-peptide-thioesters
#27
JOURNAL ARTICLE
Kimberly Perry, Binglin Sui, Yangmei Li
The revival of peptide-based drugs has led to the increasing demand for the development of large-scale synthesis of these complex molecules. To meet this demand, the use of mercapto-functionalized polyhedral oligomeric silsesquioxane (POSS-SH) as a soluble support for the synthesis of a model pentapeptide POSS-thioester is reported. The synthetic process provided a total yield of 62% for the pentapeptide POSS-thioester and the 1H NMR spectra validated the high purity of the products. The successful synthesis of the pentapeptide POSS-thioester with high yield and purity provides a promising way to the scale-up chemical synthesis of peptide thioesters, peptides, peptide amides, cyclic peptides, and even proteins...
November 23, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34970013/sequential-iodine-mediated-diallylsilane-rearrangement-asymmetric-dihydroxylation-synthesis-and-reactions-of-enantioenriched-oxasilacycles
#28
JOURNAL ARTICLE
Christopher R Myers, Paul Spaltenstein, Lauren K Baker, Cody L Schwans, Timothy B Clark, Gregory W O'Neil
Products from an iodine-mediated diallylsilane rearrangement were taken into an asymmetric dihydroxylation (AD) reaction resulting in the formation of diastereomeric 6-membered oxasilacycles. Removal of the epimeric stereocenter among this mixture of diastereomers by elimination of iodine produced a single enantioenriched cyclic allyl silyl ether. The resulting allyl silane was then successfully engaged in several further transformations, providing an alternative means to prepare useful intermediates for enantioselective synthesis...
October 12, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34658453/cu-catalyzed-cross-coupling-of-benzylboronic-esters-and-epoxides
#29
JOURNAL ARTICLE
Sophia G Gierszal, Timothy J Barker
A reaction between epoxides and benzylboronic acid pinacol esters is described. CuI was found to be an effective catalyst of this transformation upon activation of the benzylboronic ester with an alkyllithium reagent. The reaction was very efficient and a variety of substituted epoxides were found to be good substrates with good regioselectivity for substitution at the less substituted side of the epoxide. A reaction using an enantioenriched secondary benzylboronic ester was found to not be stereospecific.
October 12, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34924634/design-and-synthesis-of-3-3-triazolyl-biisoquinoline-n-n-dioxides-via-hiyama-cross-coupling-of-4-trimethylsilyl-1-2-3-triazoles
#30
JOURNAL ARTICLE
Shiyu Sun, Carlyn Reep, Chenrui Zhang, Burjor Captain, Roberto Peverati, Norito Takenaka
A new strategy to effectively lock the conformation of substituents at the 3,3'-positions of axial-chiral biisoquinoline N , N' -dioxides was developed based on the strong dipole-dipole interaction between 1,2,3-triazole and pyridine N -oxide rings. The crystal structure and the DFT calculations of 3,3'-bis(1-benzyl-1 H -1,2,3-triazole-4-yl)-1,1'-biisoquinoline N , N' -dioxide ( 3a ) provided strong support for this strategy. Furthermore, we successfully demonstrated that readily available 4-trimethylsilyl-1,2,3-triazoles are viable nucleophiles for Hiyama cross-coupling...
September 28, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34483378/convergent-synthesis-of-r-silodosin-via-decarboxylative-cross-coupling
#31
JOURNAL ARTICLE
Tie-Gen Chen, Lucas Mele, Olivier Jentzer, Dominique Delbrayelle, Pierre-Georges Echeverria, Julien C Vantourout, Phil S Baran
A new approach to Silodosin capitalizing on a radical retrosynthetic strategy to dissect the molecule into two halves is reported. Using a reductive decarboxylative cross-coupling, a simple indoline can be coupled to a chiral pool-derived fragment to arrive at the target in only seven steps (LLS). This route avoids the use of resolution strategies or asymmetric hydrogenation that requires a subsequent Curtius rearrangement to install a key amino functionality.
August 31, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34393283/indoloxytriazines-as-binding-molecules-for-the-jak2-jh2-pseudokinase-domain-and-its-v617f-variant
#32
JOURNAL ARTICLE
Ana S Newton, Maria-Elena Liosi, Sean P Henry, Luca Deiana, John C Faver, Stefan G Krimmer, David E Puleo, Joseph Schlessinger, William L Jorgensen
Small molecules that selectively bind to the pseudokinase JH2 domain over the JH1 kinase domain of JAK2 kinase are sought. Virtual screening led to the purchase of 17 compounds among which 9 were found to bind to V617F JAK2 JH2 with affinities of 40 - 300 μM in a fluorogenic assay. Ten analogues were then purchased yielding 9 additional active compounds. Aminoanilinyltriazine 22 was particularly notable as it shows no detectable binding to JAK2 JH1, and it has a 65-μM dissociation constant K d with V617F JAK2 JH2...
August 3, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34334833/formation-of-pyrroloindolines-via-the-alkylation-of-tryptamines-with-trichloroacetimidates
#33
JOURNAL ARTICLE
Bhaskar D Joshi, John D Chisholm
Pyrroloindolines and related systems are present in a large number of complex natural products. These core structures have generated considerable synthetic interest, as many of the compounds possess challenging, elaborate structures and interesting biological properties. Recently we have focused on using trichloroacetimidates for the synthesis of these fascinating molecules. Trichloroacetimidates can be used as an electrophilic source of an alkyl group to form the pyrroloindoline directly from tryptamine derivatives...
August 3, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34321699/preferential-light-chain-labeling-of-native-monoclonal-antibodies-improves-the-properties-of-fluorophore-conjugates
#34
JOURNAL ARTICLE
Michael P Luciano, Ivan Dingle, Saghar Nourian, Martin J Schnermann
Site specific labeling methods have significant potential to enhance the properties of antibody conjugates. While studied extensively in the context of antibody-drug conjugates (ADCs), few studies have examined the impact of homogenous labeling on the properties of antibody-fluorophore conjugates (AFCs). We report the application of pentafluorophenyl (PFP) esters, which had previously been shown to be reasonably selective for K188 of the kappa light chain of human IGG antibodies, toward producing AFCs. We show that simple replacement of N -hydroxy succinimide (NHS) with PFP dramatically increases the light-chain specificity of near-infrared (NIR) AFCs...
July 6, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34248214/promiscuous-pseudomonas-uptake-of-non-endogenous-ligands-for-iron-acquisition
#35
JOURNAL ARTICLE
Anna R Kaplan, William M Wuest
Iron is an essential nutrient to nearly all living beings. However, its acquisition poses a significant challenge to many organisms, including most bacteria. One of the main iron uptake strategies employed by bacteria is the uptake of siderophores, small molecules that chelate extracellular iron. The pathogenic species Pseudomonas aeruginosa produces two different siderophores, pyochelin and pyoverdine. P. aeruginosa senses the amount of bioavailable extracellular iron in order to regulate the production levels of each of these two siderophores...
July 6, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34176982/rapid-synthesis-of-the-core-scaffold-of-crinane-and-haemanthamine-through-a-multi-component-approach
#36
JOURNAL ARTICLE
Nicholas P Massaro, Joshua G Pierce
A rapid synthesis of the core structures of crinane and haemanthamine has been developed, enabled by a multicomponent approach. This work constitutes a formal synthesis of crinane and sets the stage for access to both families of natural products and key analogues. A key highlight of the approach is the modularity of the core synthesis, overcoming existing challenges for these scaffolds and providing a path to explore site-selective oxidation to expand the scope of molecules accessible from common intermediates...
July 6, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34764521/refinement-of-covalent-egfr-inhibitor-azd9291-to-eliminate-off-target-activity
#37
JOURNAL ARTICLE
Elise Bouffard, Balyn W Zaro, Melissa M Dix, Benjamin Cravatt, Chi-Huey Wong
Non-small-cell lung cancer (NSCLC) is a major disease that accounts for 85% of all lung cancer cases which claimed around 1.8 billion lives worldwide in 2020. Tyrosine kinase inhibitors (TKIs) that target EGFR have been used for the treatment of NSCLC, but often develop drug resistance, and the covalent inhibitor AZD9291 has been developed to tackle the problem of drug resistance mediated by the T790M EGFR mutation; however, there is a side effect of hyperglycemia that may be due to off-target activity. This study examines analogues of AZD9291 by chemical proteomics, identifying analogues that maintain T790M-EGFR engagement while showing reduced cross-reactivity with off-targets...
June 22, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34176981/towards-a-streamlined-synthesis-of-peptides-containing-%C3%AE-%C3%AE-dehydroamino-acids
#38
JOURNAL ARTICLE
Diego A Moyá, Michael A Lee, Joseph C Chanthakhoun, Austin K LeSueur, Daniel Joaquin, Jaden D Barfuss, Steven L Castle
Investigation of a strategy to streamline the synthesis of peptides containing α,β-dehydroamino acids (ΔAAs) is reported. The key step involves generating the alkene moiety via elimination of a suitable precursor after it has been inserted into a peptide chain. This process obviates the need to prepare ΔAA-containing azlactone dipeptides to facilitate coupling of these residues. Z -dehydroaminobutyric acid ( Z -ΔAbu) could be constructed most efficiently via EDC/CuCl-mediated dehydration of Thr. Formation of Z -ΔPhe by this or other dehydration methods was unsuccessful...
June 22, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34672489/reaction-between-harmaline-and-vanillin-to-produce-dimeric-scaffoldsthat-exhibit-anti-proliferative-activity
#39
JOURNAL ARTICLE
Vishal C Birar, Gene Zaid, Brian S J Blagg
Herbal medicine is used as a complement to modern medicine for the treatment of human diseases suchas cancer, inflammation, and diabetes. Nutraceutical components in foods such as vanillin produceantioxidant and anticancer activities and many of these produce minimal adverse effects in humans.Therefore, strategies that combine both herbal medicine and nutraceutical components could producecompounds that exhibit reduced toxicity. Recently, we developed GZ16.007, which is a combination ofharmaline and curcumin that is currently undergoing clinical evaluation for the treatment of cancer...
June 8, 2021: Tetrahedron Letters
https://read.qxmd.com/read/34393282/synthesis-of-c-linked-%C3%AE-gal-and-%C3%AE-galnac-1-hydroxyalkanes-by-way-of-c2-functionality-transfer
#40
JOURNAL ARTICLE
Ernest G Nolen, Ezra S Hornik, Kendra B Jeans, Weiyu Zhong, Danielle M LaPaglia
Inspired by reports of water sculpted Tn antigen (α-GalNAc- O -Ser/Thr) epitopes and our interest in producing metabolically more stable C -linked analogs of Tn, we explored the utility of C2 functionality on α-Gal- C -alkenes to deliver hydroxyl to the pendant alkenyl chain. Toward this end, a cyclic carbonate approach gave rise to a single C -linked α-Gal-1'(S)-hydroxyethane in 3 steps, and use of a 2-(hydroxyimino)galactoside cyclization transferred an oxygen to a pendant cis -substituted C -linked alkene affording the R -configuration at the newly formed stereocenter (7:1 dr)...
June 8, 2021: Tetrahedron Letters
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