- Electronic Control of Stereoselectivity. 11. Long-Range Modulation of Stereoselection in Diels-Alder Cycloadditions of N-Methyltriazolinedione to Aryl-Substituted 9-Butadienylidenebenzonorbornenes
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Three 9-butadienylidenebenzonorbornenes (4a-c) have been synthesized and their ability to enter into Diels-Alder reaction examined.Although these substances are unreactive to a host of dienophiles, tetracyanoethylene enters into addition with 4b and 4c.However, these reactions do not allow for examination of the stereoselectivity question.When recourse was made to the more reactive N-methyltriazolinedione reagent, adducts 9 and 10 were produced in the following syn/anti ratios: 4a, 49:51; 4b, 24:76; 4c, 24:76.The chemical shifts of the N-methyl groups in the urazole segments of these adducts proved quite divergent and conducive to reliable structural assignment.The results are interpreted in terms of zwitterion intervention, with charge delocalization into the aromatic ring where this is feasible (the tetrafluoro example excluded).Because of this long-range homoaromatic stabilization, closure of the second C-N bond from the anti direction is kinetically favored.
- Paquette, Leo A.,Klinger, Francois
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- Synthesis of trans,trans,cis-fused tetracyclic skeleton via radical domino cyclization
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Limonoids are characterized by a polycyclic structure and show a wide variety of bioactivities. In particular, mesendanin L, 12-hydroxyamoorastatone, and meliatoosenin F have unique structures containing a trans-A/B/C and cis-C/D-fused tetracyclic skeleton. We synthesized the core structure of these limonoids via Mn(OAc)3 and Cu(OAc)2-mediated radical domino cyclization of an acyclic tetraene precursor having a terminal β-keto ester. To the best of our knowledge, this is the first example of the radical-mediated construction of a 6/6/6/5-membered tetracyclic skeleton.
- Furuta, Miyu,Hanaya, Kengo,Sugai, Takeshi,Shoji, Mitsuru
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Read Online
- Characterization of typical potent odorants in raw and cooked Toona sinensis (A. Juss.) M. Roem. by instrumental-sensory analysis techniques
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Toona sinensis (A. Juss.) M. Roem. (TS) possesses a unique and pleasant flavor and is consumed as a popular seasonal vegetable in certain parts of eastern and southeastern Asia. The potent odorants in raw and cooked TS were identified by combined sensory and instrumental analysis techniques, including sensory descriptive aroma profiling and two complimentary volatile isolation methods combined with gas chromatography-olfactometry (GC-O) techniques. Highly volatile odorants were determined by static headspace dilution analysis (SHDA)-GC-O, while those of intermediate- and semi-volatility were determined by solvent-assisted flavor evaporation-aroma extract dilution analysis (SAFE-AEDA). Among the numerous odorants identified by SHDA and SAFE-AEDA, (E,E)-bis-(1-propenyl) disulfide was found to be predominant in both raw and cooked TS. In agreement with results of sensory descriptive analysis, hexanal, (Z)-3-hexenal, (E)-2-hexenal and (Z)-3-hexen-1-ol contributed green, grassy and leafy aroma notes; while hydrogen sulfide, methyl thiirane, (E,E)-bis-(1-propenyl) disulfide and (E,Z)-bis-(1-propenyl) disulfide contributed pungent, sulfurous and alliaceous notes in TS.
- Yang, Wenxi,Cadwallader, Keith R.,Liu, Yuping,Huang, Mingquan,Sun, Baoguo
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p. 153 - 163
(2019/01/26)
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- A Short Access to Symmetrically α,α-Disubstituted α-Amino Acids from Acyl Cyanohydrins
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A straightforward synthesis of symmetrically α,α-disubstituted α-amino acids is presented. The key step of this process relies on the efficient double addition of Grignard reagents to acyl cyanohydrins to provide N-acyl amino alcohols selectively in good yields. The chemoselectivity of the reaction was modulated by the nature of the acyl moiety. Eleven amino acids were prepared, including the particularly simple divinylglycine, which is not easily accessible by using conventional methods.
- Boukattaya, Fatma,Caillé, Julien,Ammar, Houcine,Rouzier, Florian,Boeda, Fabien,Pearson-Long, Morwenna S. M.,Bertus, Philippe
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p. 906 - 916
(2016/03/12)
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- Dynamic kinetic asymmetric cross-benzoin additions of β-stereogenic α-keto esters
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The dynamic kinetic resolution of β-halo α-keto esters via an asymmetric cross-benzoin reaction is described. A chiral N-heterocyclic carbene catalyzes the umpolung addition of aldehydes to racemic α-keto esters. The resulting fully substituted β-halo glycolic ester products are obtained with high levels of enantio- and diastereocontrol. The high chemoselectivity observed is a result of greater electrophilicity of the α-keto ester toward the Breslow intermediate. The reaction products are shown to undergo highly diastereoselective substrate-controlled reduction to give highly functionalized stereotriads.
- Goodman, C. Guy,Johnson, Jeffrey S.
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supporting information
p. 14698 - 14701
(2014/12/11)
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- PROCESS FOR IXABEPILONE, AND INTERMEDIATES THEREOF
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The present invention relates to a novel process of making ixabepilone, ixabepilone derivatives and analogues, and intermediates thereof.
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Paragraph 0234
(2014/09/29)
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- FLAME-RETARDANT PROCESSED RESIN OBTAINED WITH A REACTIVE FLAME RETARDANT
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A reactive flame retardant which imparts excellent flame retardancy to resins even when added in a small amount and can be prevented from bleeding out; and a flame-retardant processed resin obtained with the flame retardant. The reactive flame retardant is, for example, an organophosphorus cyclic compound which is represented by the following general formula (I) and has at least one unsaturated group at ends of R 1 to R 4 . The flame-retardant processed resin is obtained by solidifying a resin composition containing this organophosphorus cyclic compound and then reacting the compound by heating or irradiation with a radiation.
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Page/Page column
(2014/01/18)
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- Development of a scalable process for DG-041, a potent EP3 receptor antagonist, via tandem heck reactions
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DG-041 is a small molecule antagonist of the EP3 receptor for prostaglandin E2 that is in clinical development for treatment of peripheral artery disease (PAD). Originally produced using a six-step synthetic procedure, process optimization led to development of a four-step sequence that is readily scalable. The key step in the optimized sequence contains two sequential Heck reactions, involving an intramolecular Heck cyclization followed by an intermolecular Heck coupling, performed in one pot to produce a highly substituted indole core.
- Zegar, Siead,Tokar, Christopher,Enache, Livia A.,Rajagopol, Venkat,Zeller, Wayne,O'Connell, Matthew,Singh, Jasbir,Muellner, Frank W.,Zembower, David E.
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p. 747 - 753
(2012/12/29)
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- Stereoselective polycyclisations of allyl and enyne silanes: Evidence for bicyclo[3.2.0]hept-1(7)ene structure
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The intramolecular copper(I)-catalyzed [2 + 2]-photocycloaddition of diphenyldiallysilane (1) (or tetraallylsilane (4)) led to sila-3-bicyclo[3.2.0]heptane (3) (or to spiro analogous 6) in the cis (or cis-cis) configuration whereas the α,ω-diiodide (2) obtained by cyclozirconation of 1 (or from the homologous tetraiodide 5) followed by addition of n-BuLi, produced the sila-3-bicyclo[3.2.0]heptane (3) (or to the spiro analogous 6) in the trans (or trans-trans configuration). The same cyclozirconation reaction, starting from the hetero enyne 7, selectively led to the highly strained silacyclobutene moiety 15 which represents the first stable hetero bicyclo[3.2.0]hept-1(7)ene skeleton, hypothetical intermediate in methathesis reactions.
- Oba, Gabriel,Moreira, Georges,Manuel, Georges,Koenig, Max
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p. 324 - 330
(2007/10/03)
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- First total synthesis of natural 6-epiplakortolide e.
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[reaction: see text] Natural 6-epiplakortolide E was first synthesized from readily available 1-bromo-10-phenyldecane in 10 steps by using singlet oxygen-mediated Diels-Alder reaction to form cyclic peroxide followed by a directed iodolactonization to give the peroxylactone core.
- Jung, Mankil,Ham, Jungyeob,Song, Jueun
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p. 2763 - 2765
(2007/10/03)
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- Total synthesis of rutamycin B, a macrolide antibiotic from Streptomyces aureofaciens
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Rutamycin B (2) was synthesized from three principal subunits, spiroketal 75, keto aldehyde 83, and aldehyde 108. First, triol 62 was assembled by Julia coupling of sulfone 56 with aldehyde 58 followed by an acid-catalyzed spiroketalization. The three hydroxyl functions of 62 were successfully differentiated, leading to phosphonate 75. The latter was condensed in a Wadsworth-Emmons reaction with 83, prepared in six steps from (R)-aldehyde 76, to give 92. Coupling of the titanium enolate of 92 with 108 afforded Felkin product 109 with high stereoselectivity in a process that is critically dependent on the presence of the p-methoxybenzyl ether in the aldehyde. Transformation of 109 via aldehyde 116 to vinylboronate 122 was followed by macrocyclization under Suzuki conditions to yield 123. Exhaustive desilylation of the latter yielded rutamycin B.
- White,Hanselmann,Jackson,Porter,Ohba,Tiller,Wang
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p. 5217 - 5231
(2007/10/03)
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- Nodulisporic acid derivatives
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The present invention relates to novel nodulosporic acid derivatives, which are acaricidal, antiparasitic, insecticidal and anthelmintic agents.
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- Process for preparing 1-bromoalkylbenzene derivatives and intermediates thereof
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A 1-bromoalkylbenzene derivative is prepared by reacting a phenylalkene derivative with hydrogen bromide in the presence of a non-polar solvent. The phenylalkene derivative is prepared by reacting an alkenyl halide with metal magnesium to form a Grignard reagent, and then reacting the Grignard reagent with a benzyl halide derivative. An allyl Grignard reagent is prepared by reacting continuously an allyl halide derivative with metal magnesium in an organic solvent, in which the allyl halide derivative and metal magnesium are continuously added to the reaction system and the allyl Grignard reagent formed is continuously removed from the reaction system. The processes provide the intended compounds in high yields, high selectivities and high purities.
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- Infrared and nuclear magnetic resonance spectroscopic studies of the structure and dynamics of allylic magnesium compounds
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The infrared spectra of allyl- and methallyl-d2-magnesium bromides have two double bond stretching bands, corresponding to C=CH2 and C=CD2 groups in equilibrating allylic isomers. The methylene resonances in the 13C NMR spectra of allylmagnesium bromide and chloride and methallylmagnesium bromide are broadened at low temperatures by an exchange process which appears to be the interconversion between the classical unsymmetrical allylic structures. Analogous changes are seen in the spectrum of 1,3-dimethylallylmagnesium chloride and in the proton NMR spectrum of allylmagnesium bromide. Rate constants and activation parameters for the exchange have been determined from the line broadenings. Unlike the Grignard reagent, the methylene resonances of diallylmagnesium in tetrahydrofuran are not significantly broadened at reduced temperature, and the deuterated reagent does not have two distinct double bond stretching bands in the IR spectrum.
- Hill, E. Alexander,Boyd, Winston A.,Desai, Hemnalini,Darki, Amir,Bivens, Lymel
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- Maleic anhydride derivatives used as conjugation agents of anti-tumor agents on desired carriers
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The present invention relates to anti-tumor-conjugation agent-protein compounds of the general formula I: STR1 wherein, R1 and R2 are each independently selected from hydrogen atom, C1-4 alkyl, C1-4 alkoxy, C1-6 carboxyalkyl, phenyl, or phenyl substituted by at least one of hydroxy, halogen, lower alkyl, lower alkoxy, or nitro, with the proviso that R1 and R2 cannot be simultaneously a hydrogen, and when one of R1 or R2 is a hydrogen, the other one cannot be --CH2 COOH; A is the residue of an anti-tumor agent containing at least one amino group available to form an amide bound; and B is a free ε-lysine containing residue selected from a peptide or a protein.
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- SPIROFURANE DERIVATIVES
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Compounds of general formula I, STR1 wherein R 1 represents hydrogen or alkyl C 1-3,R 2 represents hydrogen or alkyl C 1-6,n and m are integers from 1 to 3, provided that n+m=4, andone of X and Y represents CH. sub.2 and the other represents CHR 3, C=O, C=CHR 4 or C. dbd.NR 5, in whichR 3, R. sup.4 and R 5 are as defined in the specification, and their salts are useful as pharmaceuticals, in particular as central muscarinic acetylcholine receptors. The compounds are therefore useful in the treatment of diseases such as presenile and senile dementia, Huntington's chorea, tardive dyskinesia, hyperkinesia, mania and Tourette Syndrome, and also as analgesic agents for use in the treatment of severe painful conditions such as rheumatism, arthritis, and terminal illness.
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- Use of Magnesium Anthracene * 3 THF in Synthesis: Generation of Grignard Compounds and Other Reactions with Organic Halides
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The course (a), (b), (c) (Scheme 1) of the reaction of magnesium anthracene * 3 THF (1) with organic halides (RX) is dependent on the nature of RX.With alkyl halides in THF 1 reacts as a nucleophile, whereby primary as well as secondary alkyl halides produce dialkyldihydroanthracenes (4-4'') and tertiary alkyl halides yield primarily monoalkyl-substituted dihydroanthracenes (2, 2').With bromo- and iodobenzene in THF 1 reacts predominantly as a radical with H atom abstraction from the solvent affording benzene and 9.The formation of Grignard compounds (5) and anthracene (6), originating from primary and secondary alkyl and aryl halides and 1 in toluene or ether at elevated temperatures, is not caused by the reaction of 1 but by the "active magnesium" (Mg*) formed by decomposition of 1 in these solvents.In contrast, allyl, propargyl, and benzyl halides react with 1 independently of the solvent under mild conditions to produce 5 and 6.Allyl- and the difficultly accessible allenylmagnesium chloride can be prepared in THF at -78 and 0 deg C, respectively, from the corresponding halides and ordinary Mg powder via catalytic amounts of 1.
- Bogdanovic, Borislav,Janke, Nikolaus,Kinzelmann, Hans-Georg
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p. 1507 - 1515
(2007/10/02)
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- Active Magnesium from Catalytically Prepared Magnesium Hydride or from Magnesium Anthracene and its Uses in the Synthesis
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Highly reactive, pyrophoric forms of magnesium with specific surface areas of 20-109 m2/g (Mg*) can be generated by the dehydrogenation of catalytically prepared magnesium hydride (MgH2*) or by decomposition of magnesium anthracene * 3 THF (4).The decomposition of 4, with recovery of anthracene and THF, may be accomplished both thermally and by ultrasound in an organic solvent (toluene, n-heptane) or thermally in the solid state in vacuo.Mg* obtained by the latter method exhibits only weak reflections in the X-ray powder diagram and has, in comparison to other mentioned Mg* species, the highest reactivity toward hydrogen.Diverse Grignard compounds can be prepared under mild conditions (* from MgH2* or 4.The cleavage of THF with formation of 1-oxa-2-magnesiacyclohexane (2) is possible by employing Mg* from NgH2* or 4.
- Bartmann, Ekkehard,Bogdanovic, Borislav,Janke, Nikolaus,Liao, Shijan,Schlichte, Klaus,et al.
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p. 1517 - 1528
(2007/10/02)
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- Triazole alkanols having fungicidal and plant growth regulating properties
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Compounds of formula: STR1 and stereo isomers thereof, wherein R is optionally substituted phenyl, alkyl or cycloalkyl and R1 and R2 are hydrogen or alkyl, alkenyl or alkynyl groups; Z is a straight or branched chain aliphatic group containing at least double or triple bond and optionally substituted with halogen, hydroxy, alkoxy or alkylthio; n is 1,2,3, or 4; and acid addition salts, ethers, esters and metal complexed thereof; having fungicidal and plant growth regulating activity.
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- A DIRECT SYNTHESIS OF 1,3-BIS(BROMOMAGNESIO)PROPANE
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Careful addition of 1,3-dibromopropane (2) to magnesium in Et2O yields 1,3-bis(bromomagnesio)propane (1) which is purified via "magnesacyclobutane" (5).Reactions of 1 with H2O, CO2, HgBr2 and Me3SnCl are reported.MgBr2 catalyzes the decomposition of 1 to allylmagnesium bromide (4).
- Seetz, J.W.F.L.,Hartog, F.A.,Boehm, H.P.,Blomberg, C.,Akkerman, O.S.,Bickelhaupt, F.
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p. 1497 - 1500
(2007/10/02)
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- Antiandrogenic 17α-substituted steroids
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17α-substituted steroids of the formula STR1 wherein R1 is hydrogen, acyl, alkyl, alkenyl, alkyl or alkenyl interrupted by an oxygen atom, cyclopentyl, or tetrahydropyranyl, R2 is alkyl or alkenyl of 2-6 carbon atoms, X is oxygen or the grouping H(OR3) wherein R3 is hydrogen, acyl, alkyl, alkenyl, alkyl or alkenyl interrupted by an oxygen atom, cyclopentyl, or tetrahydropyranyl, upon topical application, display antiandrogenic properties and can be utilized for the treatment of acne, seborrhea, alopecia and hirsutism.
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- Thermochemical Bond Dissociation Energies of Carbon-Magnesium Bonds
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The heats of formation of 29 alkylmagnesium bromides, isobutyl bromide, and neopentyl bromide have been determined, and bond dissociation energies have been derived for the Grignard reagents.For saturated alkyl derivatives the C-Mg bond strength decreases with an increasing number of β-hydrogens in the series methyl, neopentyl, isobutyl, butyl, ethyl, 1-ethylpropyl, 1-methylpropyl, isopropyl, and t-butyl.Bonding in alkyl bromides and alkylmagnesium bromides is discussed.
- Holm, Torkil
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p. 464 - 467
(2007/10/02)
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- Polycyclic compounds
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Tricyclo[4.2.1.02,5 ]non-7-enes wherein the 3 position is substituted by a methylol group may be made by reacting a bicyclo[2.2.1]hepta-2,5-diene with a 2-alkenyl magnesium compound in a 1:1 ratio to yield a molecular addition product which is then oxidized and hydrolyzed to give the 3-methylol product. These substituted tricyclo[4.2.1.02,5 ]non-7-enes are useful, inter alia, as intermediates for the manufacture of lubricating oil additives and various other useful products and they may be used for gas scrubbing applications and the like.
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- Tricyclic compounds
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1-Methyl(or acetyl)-5H-dibenzo[a,d]cycloheptenes and 1-methyl(or acetyl)-10,11-dihydro-5H-dibenzo[a,d]cycloheptenes bearing a basic side chain at the 5-position, such as a 3-mono- or dimethylaminopropylidene, a 3-mono- or dimethylaminopropyl or a 3-dimethylaminopropylidene(or propyl)-N-oxide, intermediates and processes for their preparation, are described. The end products are useful antidepressants.
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