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https://www.readbyqxmd.com/read/27681860/asymmetric-synthesis-of-dipropionate-derivatives-through-catalytic-hydrogenation-of-enantioenriched-e-ketene-heterodimers
#1
Shi Chen, Mukulesh Mondal, Ahmad A Ibrahim, Kraig A Wheeler, Nessan J Kerrigan
A highly diastereoselective approach to dipropionate derivatives through Pd/C-catalyzed hydrogenation of enantioenriched E-ketene heterodimers is described. Catalytic hydrogenation of the E-isomer of ketene heterodimer β-lactones (12 examples) provides access to syn,anti-β-lactones (dipropionate derivatives) bearing up to three stereogenic centers (dr up to 49:1), and with excellent transfer of chirality (ee up to >99%).
August 2016: Synthesis
https://www.readbyqxmd.com/read/27482123/improved-synthesis-of-mdl-73811-a-potent-adometdc-inhibitor-and-anti-trypanosomal-compound
#2
Anthony J Brockway, Casey C Cosner, Oleg A Volkov, Margaret A Phillips, Jef K De Brabander
An improved synthesis of MDL 73811 - a potent AdoMetDC (S-adenosylmethionine decarboxylease) inhibitor and anti-trypanosomal compound with in vivo activity has been completed in four steps from commercially available 2',3'-O-isopropylideneadenosine. Utilization of Mitsunobu chemistry was crucial for the reliable and scalable introduction of the 5'-methylamine moiety, which was problematic using traditional activation/displacement chemistry as previously reported. All reactions in this synthesis were run on gram-scale resulting in a five-fold increase in yield over the original synthesis...
July 2016: Synthesis
https://www.readbyqxmd.com/read/27413246/synthesis-of-5-hydroxymethylcytidine-and-5-hydroxymethyl-uridine-modified-rna
#3
Christian Riml, Ronald Micura
We report on the syntheses of 5-hydroxymethyl-uridine [5hm(rU)] and -cytidine [5hm(rC)] phosphoramidites and their incorporation into RNA by solid-phase synthesis. Deprotection of the oligonucleotides is accomplished in a straightforward manner using standard conditions, confirming the appropriateness of the acetyl protection used for the pseudobenzylic alcohol moieties. The approach provides robust access to 5hm(rC/U)-modified RNAs that await applications in pull-down experiments to identify potential modification enzymes...
April 2016: Synthesis
https://www.readbyqxmd.com/read/27152053/acetoxy-substituted-cyclopropane-dicarbonyls-as-stable-donor-acceptor-acceptor-cyclopropanes
#4
Yahaira Reyes, Keith T Mead
A study of cyclopropanations of oxy-substituted ethenes with ethyl α-diazoaroyl acetates is described. Whereas trimethylsilyl vinyl ether and ethyl vinyl ether gave dihydrofuran products, stable cyclopropanes were isolated when vinyl acetate was used. Yields ranged from 0-87%, depending on the nature and position of the aryl ring substituent.
October 2015: Synthesis
https://www.readbyqxmd.com/read/26806984/iron-catalyzed-diastereoselective-intramolecular-olefin-aminobromination-with-bromide-ion
#5
Jun-Shan Tian, Cheng-Liang Zhu, Yun-Rong Chen, Hao Xu
A new iron-catalyzed diastereoselective aminobromination method is reported for both internal and terminal olefins (yield up to 90% and dr up to >20:1). In this transformation, a functionalized hydroxylamine and bromide ion were used as the nitrogen and bromine source, respectively. This method is compatible with a broad range of olefins and provides a convenient approach to synthetically valuable vicinal bromo primary amines. Our studies suggest that both the diastereoselectivity and enantioselectivity for the olefin aminobromination can be controlled by iron catalysts...
June 2015: Synthesis
https://www.readbyqxmd.com/read/26568642/synthesis-of-a-series-of-novel-3-9-disubstituted-phenanthrenes-as-analogues-of-known-nmda-receptor-allosteric-modulators
#6
Mark W Irvine, Guangyu Fang, Richard Eaves, Maria B Mayo-Martin, Erica S Burnell, Blaise M Costa, Georgia R Culley, Arturas Volianskis, Graham L Collingridge, Daniel T Monaghan, David E Jane
9-Substituted phenanthrene-3-carboxylic acids have been reported to have allosteric modulatory activity at the NMDA receptor. This receptor is activated by the excitatory neurotransmitter L-glutamate and has been implicated in a range of neurological disorders such as schizophrenia, epilepsy and chronic pain and neurodegenerative disorders such as Alzheimer's disease. Herein, the convenient synthesis of a wide range of novel 3,9-disubstituted phenanthrene derivatives starting from a few common intermediates is described...
June 1, 2015: Synthesis
https://www.readbyqxmd.com/read/26508806/rhodium-catalyzed-intermolecular-5-1-and-5-2-cycloadditions-using-1-4-enynes-with-an-electron-donating-ester-on-the-3-position
#7
Casi M Schienebeck, Wangze Song, Angela M Smits, Weiping Tang
Various 3-acyloxy-1,4-enynes could be employed in rhodium-catalyzed intermolecular [5+1] and [5+2] cycloadditions with CO or alkynes, respectively. The rate of these cycloadditions could be accelerated significantly by using 1,4-enynes with an electron-donating ester on the 3-position. The scope of rhodium-catalyzed [5+1] and [5+2] cycloadditions were examined by using 1,4-enynes bearing an electron-donating ester.
May 2015: Synthesis
https://www.readbyqxmd.com/read/26752794/an-asymmetric-organocatalytic-quadruple-domino-reaction-employing-a-vinylogous-friedel-crafts-michael-michael-aldol-condensation-sequence
#8
Arne R Philipps, Lars Fritze, Nico Erdmann, Dieter Enders
An organocatalytic quadruple cascade initiated by a Friedel-Crafts-type reaction is described. The (S)-diphenylprolinol trimethylsilyl ether catalyzed reaction yields highly functionalized cyclohexenecarbaldehydes bearing a 1,1-bis[4-(dialkylamino)phenyl]ethene moiety and three contiguous stereogenic centers. The reaction tolerates various functional groups and all products are obtained with very good diastereoselectivity and with virtually complete enantiomeric excess.
April 2, 2015: Synthesis
https://www.readbyqxmd.com/read/27003951/efficient-syntheses-of-vitamin-k-chain-shortened-acid-metabolites
#9
Aaron M Teitelbaum, Michele Scian, Wendel L Nelson, Allan E Rettie
Vitamin K sequentially undergoes ω-oxidation followed by successive rounds of β-oxidation to ultimately produce two chain-shortened carboxylic acid metabolites, vitamin K acid 1 and vitamin K acid 2. Two facile syntheses of these acid metabolites are described, each starting from commercially available menadione-cyclopentadiene adduct 3. Vitamin K acid 1 was synthesized in five steps via alkylation with a geranyl halide followed by subsequent oxidation reactions, while fully retaining the trans configuration of the side chain 2',3'-double bond...
April 2015: Synthesis
https://www.readbyqxmd.com/read/26722133/organocatalytic-asymmetric-domino-michael-henry-reaction-of-indolin-3-ones-with-o-formyl-%C3%AE-nitrostyrenes
#10
Suruchi Mahajan, Pankaj Chauhan, Charles C J Loh, Server Uzungelis, Gerhard Raabe, Dieter Enders
A highly diastereo- and enantioselective domino Michael/Henry reaction of 1-acetylindolin-3-ones with o-formyl-(E)-β-nitrostyrenes catalyzed by low loading of a quinine-derived amine-squaramide provides the corresponding indolin-3-one derivatives bearing four adjacent stereogenic centers in good to high yields and with excellent stereoselectivities.
April 1, 2015: Synthesis
https://www.readbyqxmd.com/read/26722132/organocatalytic-asymmetric-synthesis-of-dihydroisoquinolinones-via-a-one-pot-aza-henry-hemiaminalization-oxidation-sequence
#11
Robert Hahn, Ehsan Jafari, Gerhard Raabe, Dieter Enders
The asymmetric organocatalytic one-pot synthesis of trans-3,4-disubstituted 3,4-dihydroisoquinolin-1(2H)-ones is described. Starting from 2-(nitromethyl)benzaldehydes and various N-protected aldimines, 5 mol% of a quinine-based squaramide organocatalyst was used to synthesize the title compounds as virtually single diastereomers via an aza-Henry-hemiaminalization-oxidation sequence. Moderate to good yields (39-78%) and moderate to very good enantioselectivities (40-95% ee) were reached.
February 1, 2015: Synthesis
https://www.readbyqxmd.com/read/25598556/-3-2-cycloaddition-reactions-of-oxyallyl-cations
#12
Hui Li, Jimmy Wu
The (3+2)-cycloaddition reaction involving oxyallyl cations has proven to be a versatile and efficient approach for the construction of five-membered carbo- and heterocycles, which are prevalent frameworks in natural products and pharmaceuticals. The following article will provide a brief summary of recent disclosures on this process featuring chemo-, regio- and diastereoselective oxyallyl cycloadditions with both electron-rich and electron-deficient 2π partners.
January 2015: Synthesis
https://www.readbyqxmd.com/read/26752795/asymmetric-n-heterocyclic-carbene-catalyzed-annulation-of-2-alkenylbenzothiazoles-with-%C3%AE-chloro-aldehydes
#13
Xiaoxiao Song, Qijian Ni, Chen Zhu, Gerhard Raabe, Dieter Enders
Diastereo- and enantioselective N-heterocyclic carbene catalyzed 1-azadiene Diels-Alder reactions of (E)-2-styrylbenzothiazoles with α-chloro aldehydes are reported. This annulation strategy provides an efficient access to medicinally important dihydrobenzothiazolopyridin-1-ones in good to excellent yields (44-97%) with very good to excellent stereoselectivities (up to 9:1 dr, 98% ee) and tolerates quite a range of substituents.
November 6, 2014: Synthesis
https://www.readbyqxmd.com/read/25177061/syntheses-of-3-alkylamino-methylene-6-methylpyridine-2-4-1h-3h-diones-3-substituted-7-methyl-2h-pyrano-3-2-c-pyridine-2-5-6h-dione-fluorescence-probes-and-tetrahydro-1h-9h-2-10-dioxa-9-azaanthracen-1-ones
#14
Allan M Prior, Medha J Gunaratna, Daisuke Kikuchi, John Desper, Yunjeong Kim, Kyeong-Ok Chang, Izumi Maezawa, Lee-Way Jin, Duy H Hua
Various condensation and ring-closing reactions were used for the syntheses of 3-[(alkylamino)methylene]-6-methylpyri-dine-2,4(1H,3H)-diones, bicyclic pyridinones, and tricyclic morpholinopyrones. For instance, 3-[(dialkylamino)methylene]-6-methylpyridine-2,4(1H,3H)-diones were synthesized from the condensation of dialkylamines and 3-formyl-4-hydroxy-6-methylpyridin-2(1H)-one. 3-Formyl-4-hydroxy-6-methylpyridin-2(1H)-one, derived from 3-formyl-4-hydroxy-6-methylpyridin-2(1H)-one, was used to construct a number of bicyclic pyridinones via a one-pot Knoevenagal and intramolecular lactonization reaction...
August 2014: Synthesis
https://www.readbyqxmd.com/read/25294948/copper-catalyzed-decarboxylative-trifluoromethylation-of-propargyl-bromodifluoroacetates
#15
Brett R Ambler, Santosh Peddi, Ryan A Altman
The development of efficient methods for accessing fluorinated functional groups is desirable. Herein, we report a two-step method that utilizes catalytic Cu for the decarboxylative trifluoromethylation of propargyl bromodifluoroacetates. This protocol affords a mixture of propargyl trifluoromethanes and trifluoromethyl allenes.
July 15, 2014: Synthesis
https://www.readbyqxmd.com/read/25278633/an-asymmetric-organocatalytic-quadruple-cascade-to-tetraaryl-substituted-2-azabicyclo-3-3-0-octadienones
#16
Céline Joie, Kristina Deckers, Gerhard Raabe, Dieter Enders
A new asymmetric organocatalytic three-component quadruple cascade of α-ketoamides with α,β-unsaturated aldehydes is described. The reaction is catalyzed by the (S)-diphenylprolinol TMS ether catalyst and proceeds via an aza-Michael/aldol condensation/vinylogous Michael/aldol condensation sequence to yield tetraaryl-substituted 2-azabicyclo[3.3.0]octadienone derivatives. The cascade products are obtained with good to very good yields (34-71%), virtually complete diastereoselectivities (>20:1), and very good enantioselectivities (84-97%)...
June 1, 2014: Synthesis
https://www.readbyqxmd.com/read/25284900/asymmetric-synthesis-of-functionalized-dihydro-and-tetrahydropyrans-via-an-organocatalytic-domino-michael-hemiacetalization-reaction
#17
Gregor Urbanietz, Iuliana Atodiresei, Dieter Enders
Starting from α-hydroxymethyl nitroalkenes and various 1,3-dicarbonyl compounds, a one-pot organocatalyzed diastereo- and enantioselective synthesis of polyfunctionalized dihydro- and tetrahydropyran derivatives via a domino Michael-hemiacetalization sequence is reported. The title compounds bearing a variety of functional groups can be synthesized in this way in good yields (59-91%) and with moderate to excellent diastereoselectivities (26-98% de) and enantioselectivities (71-99% ee).
May 1, 2014: Synthesis
https://www.readbyqxmd.com/read/25278634/organocatalytic-asymmetric-synthesis-of-functionalized-1-3-5-triarylpyrrolidin-2-ones-via-an-aza-michael-aldol-domino-reaction
#18
Céline Joie, Kristina Deckers, Dieter Enders
The organocatalytic asymmetric synthesis of functionalized 1,3,5-triarylpyrrolidin-2-ones bearing three contiguous stereocenters through an aza-Michael/aldol domino reaction of α-ketoamides with α,β-unsaturated aldehydes is described. The domino products were further derivatized by aldehyde olefination under one-pot conditions. The reaction proceeds with excellent diastereoselectivities (>20:1) and good to excellent enantioselectivities (60-96% ee).
March 1, 2014: Synthesis
https://www.readbyqxmd.com/read/24914246/efficient-and-scalable-synthesis-of-4-carboxy-pennsylvania-green-methyl-ester-a-hydrophobic-building-block-for-fluorescent-molecular-probes
#19
Zachary R Woydziak, Liqiang Fu, Blake R Peterson
Fluorinated fluorophores are valuable tools for studies of biological systems. However, amine-reactive single-isomer derivatives of these compounds are often very expensive. To provide an inexpensive alternative, we report a practical synthesis of 4-carboxy-Pennsylvania Green methyl ester. Derivatives of this hydrophobic fluorinated fluorophore, a hybrid of the dyes Oregon Green and Tokyo Green, are often cell permeable, enabling labeling of intracellular targets and components. Moreover, the low pKa of Pennsylvania Green (4...
January 1, 2014: Synthesis
https://www.readbyqxmd.com/read/25221358/substituted-2-2-bipyridines-by-nickel-catalysis-4-4-di-tert-butyl-2-2-bipyridine
#20
Joseph A Buonomo, Daniel A Everson, Daniel J Weix
A simple, ligand-free synthesis of the important bipyridyl ligand 4,4'-di-tert-butyl-2,2'-bipyridine is presented. 5,5'-bis(trifluoromethyl)-2,2'-bipyridine is also synthesized by the same protocol. The syntheses efficiently couple the parent 2-chlorpyridies by a nickel-catalyzed dimerization with manganese powder as the terminal reductant.
November 1, 2013: Synthesis
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