- Synthesis of (±)-rosaprostol
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A total synthesis of racemic rosaprostol, an untiulcer drug, has been achieved in seven synthetic steps and in 42% overall yield starting from dimethyl methanephosphonate. The key steps include intramolecular carbenoid cyclization of dimethyl 1-diazo-2-oxoundecanephosphonate 4 leading to 2- dimethoxyphosphoryl-3-hexylcyclopentanone 5 and the Horner-Wittig reaction of the latter with methyl 5-formylpentanecarboxylate 6 employed for the introduction of the methoxycarbonylhexyl moiety at C(2) of the cyclopentanone ring.
- Mikolajczyk, Marian,Zurawinski, Remigiusz
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- α-nitrocycloalkanones as a new source for the one-pot synthesis of functionalized 1,4-diketones, γ-oxoaldehydes, γ-ketoesters, and methyl ω- oxoalkanoates
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Methyl ω-oxoalkanoates were obtained via ring cleavage of α- nitrocycloakanones by refluxing these compounds in a methanolic solution of KOH, then treating the obtained mixture, at 0 °C, with an aqueous solution of KMnO4/MgSO4. 1,4-Diketones, γ-oxoaldehydes, and γ-ketoesters were also prepared by conjugated addition of α-nitrocycloakanones to the appropriate conjugated enones, in MeOH/Ph3P, then by, in situ, ring cleavage-Nef reaction following the above conditions.
- Ballini, Roberto,Bosica, Giovanna,Gigli, Fabiola
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- Iridium-catalyzed enantioselective allylic substitution of unstabilized enolates derived from α,β-unsaturated ketones
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We report Ir-catalyzed, enantioselective allylic substitution reactions of unstabilized silyl enolates derived from α,β-unsaturated ketones. Asymmetric allylic substitution of a variety of allylic carbonates with silyl enolates gave allylated products in 62-94% yield with 90-98% ee and >20:1 branched-to-linear selectivity. The synthetic utility of this method was illustrated by the short synthesis of an anticancer agent, TEI-9826.
- Chen, Ming,Hartwig, John F.
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- Synthesis and biological evaluations of marine oxohexadecenoic acids: PPARα/γ dual agonism and anti-diabetic target gene effects
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Obesity and associated disorders such as metabolic syndrome and type 2 diabetes (T2D) have reached epidemic proportions. Several natural products have been reported as Peroxisome Proliferator-Activated Receptor (PPAR) agonists, functioning as lead compounds towards developing new anti-diabetic drugs due to adverse side effects of existing PPAR drugs. We recently isolated and identified (7E)-9-oxohexadec-7-enoic acid (1) and (10E)-9-oxohexadec-10-enoic acid (2) from the marine algae Chaetoceros karianus. Herein we report the total synthesis, pharmacological characterization, and biological evaluations of these naturally occurring oxo-fatty acids (oFAs). The syntheses of 1 and 2 afforded sufficient material for extensive biological evaluations. Both oFAs show an appreciable dose-dependent activation of PPARα and -γ with EC50 values in the micromolar range, and an ability to regulate important PPAR target genes in hepatocytes and adipocytes. Moreover, both 1 and 2 are able to drive adipogenesis when evaluated in the Simpson-Golabi-Behmel syndrome (SGBS) pre-adipocyte cell model, but with lowered expression of adipocyte markers and reduced lipid accumulation compared to the drug rosiglitazone. This seems to be caused by a transient upregulation of PPARγ and C/EBPα expression. Importantly, whole transcriptome analysis shows that both compounds induce anti-diabetic gene programs in adipocytes by upregulating insulin-sensitizing adipokines and repressing pro-inflammatory cytokines.
- S?ther, Thomas,Paulsen, Steinar M.,Tungen, J?rn E.,Vik, Anders,Aursnes, Marius,Holen, Torgeir,Hansen, Trond Vidar,Nebb, Hilde I.
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- Stereoselective synthesis of MaR2n-3 DPA
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The first total synthesis of the n-3 docosapentaenoic derived oxygenated product MaR2n-3 DPA has been achieved. The 13R and 14S stereogenic centers were introduced using 2-deoxy-D-ribose in a chiral pool strategy. The geometry of the Z,E,E-triene moiety was prepared using highly E-selective Wittig- and Takai-olefination reactions as well as the Z-stereoselective Lindlar reduction. LC/MS-MS data of synthetic MaR2n-3 DPA matched data for the biosynthetic formed product that enabled the configurational assignment of this oxygenated natural product to be (7Z,9E,11E,13R,14S,16Z,19Z)-13,14-dihydroxydocosa-7,9,11,16,19-pentaenoic acid.
- S?nderskov, Jeanne,Tungen, J?rn E.,Palmas, Francesco,Dalli, Jesmond,Serhan, Charles N.,Stenstr?m, Yngve,Vidar Hansen, Trond
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- Investigation of (S)-(-)-acidomycin: A selective antimycobacterial natural product that inhibits biotin synthase
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The synthesis, absolute stereochemical configuration, complete biological characterization, mechanism of action and resistance, and pharmacokinetic properties of (S)-(-)-acidomycin are described. Acidomycin possesses promising antitubercular activity against a series of contemporary drug susceptible and drug-resistant M. tuberculosis strains (minimum inhibitory concentrations (MICs) = 0.096-6.2 μM) but is inactive against nontuberculosis mycobacteria and Gram-positive and Gram-negative pathogens (MICs > 1000 μM). Complementation studies with biotin biosynthetic pathway intermediates and subsequent biochemical studies confirmed acidomycin inhibits biotin synthesis with a Ki of approximately 1 μM through the competitive inhibition of biotin synthase (BioB) and also stimulates unproductive cleavage of S-adenosyl-l-methionine (SAM) to generate the toxic metabolite 5′-deoxyadenosine. Cell studies demonstrate acidomycin selectively accumulates in M. tuberculosis providing a mechanistic basis for the observed antibacterial activity. The development of spontaneous resistance by M. tuberculosis to acidomycin was difficult, and only low-level resistance to acidomycin was observed by overexpression of BioB. Collectively, the results provide a foundation to advance acidomycin and highlight BioB as a promising target.
- Bockman, Matthew R.,Engelhart, Curtis A.,Cramer, Julia D.,Howe, Michael D.,Mishra, Neeraj K.,Zimmerman, Matthew,Larson, Peter,Alvarez-Cabrera, Nadine,Park, Sae Woong,Boshoff, Helena I. M.,Bean, James M.,Young, Victor G.,Ferguson, David M.,Dartois, Veronique,Jarrett, Joseph T.,Schnappinger, Dirk,Aldrich, Courtney C.
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p. 598 - 617
(2019/02/14)
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- Chiral geminal disilyl alkane compound, synthesis method and applications thereof
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The present invention discloses a chiral geminal disilyl alkane compound, which is represented by a formula V, wherein * represents a chiral carbon atom in the formula V. The invention discloses a synthesis method of the chiral geminal disilyl alkane compound, wherein the synthesis method comprises: carrying out a reaction in the presence of a reducing agent by using alkyne represented by a formula I, dihydrosilane represented by a formula II and trihydrosilane represented by a formula III as raw materials and using Xantphos-CoBr2 and a chiral CoX2-OIP complex as catalysts under an inert gas to prepare the chiral geminal disilyl alkane compound represented by the formula V. According to the present invention, the method has characteristics of mild reaction condition, simple operation, highatomic economy, no requirement of the addition of any other toxic transition metals (such as ruthenium, rhodium, palladium and the like) salts, high yield and high enantioselectivity, and has great practical value in the synthesis of drugs and materials, wherein the yield is generally 50-85%, and the enantioselectivity is generally 93-99%. The formulas I, II, III and V are defined in the specification.
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Paragraph 0204; 0205; 0206; 0207; 0210
(2019/01/14)
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- Racemic gem disilyl alkane compound containing four silicon-hydrogen bonds, and sybthesis method and application of compound
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The invention discloses a racemic gem disilyl alkane compound containing four silicon-hydrogen bonds. The compound is as shown in a formula IV. The invention further discloses a synthesis method of the racemic gem disilyl alkane compound. The synthesis method comprises the following step of carrying out a reaction by taking alkyne as shown in a formula I and trihydrosilane as shown in a formula IIas raw materials and taking a chiral CoX-IIP complex as a catalyst in the presence of a reducing agent to obtain the racemic gem disilyl alkane compound containing four silicon-hydrogen bonds, wherein the compound is as shown in the formula IV. The method disclosed by the invention has mild reaction conditions, is simple and convenient to operate and has high atom economy. In addition, the reaction does not need addition of any salts of toxic transition metals (such as ruthenium, rhodium, palladium and the like), and the method has a relatively large practical application value in synthesis of medicines and materials. In addition, the reaction has a medium to excellent yield (51-99%) and high area selectivity (10:1-19:1, most parts larger than 19:1).
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Paragraph 0263-0268; 0270
(2019/05/15)
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- Linear Selective Isomerization/Hydroformylation of Unsaturated Fatty Acid Methyl Esters: A Bimetallic Approach
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Herein, we report about the development of an isomerization/hydroformylation tandem reaction to selectively convert fatty acid methyl esters into asymmetric α,ω-functionalized aldehyde esters. An orthogonal tandem catalytic system consisting of a palladium-based isomerization catalyst and a rhodium-based hydroformylation catalyst was developed, using methyl 3-hexenoate as a model substrate. Using this catalyst, high yields (81% at 99% conversion) and regioselectivities (l/b-ratio of 98/2) toward the desired terminal hydroformylation product are obtained in the conversion of methyl 3-hexenoate under mild conditions. Ethyl 4-decenoate was subsequently applied as a second model substrate to identify challenges associated with the longer chain length of the unsaturated ester. Finally, methyl oleate was converted using the developed catalyst system. High aldehyde yields of 74% (at 99% conversion) with an l/b-ratio of 91/9 are obtained.
- Gaide, Tom,Bianga, Jonas,Schlipk?ter, Kim,Behr, Arno,Vorholt, Andreas J.
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p. 4163 - 4171
(2017/06/19)
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- Discovery of a highly potent anti-inflammatory epoxyisoprostane-derived lactone
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Epoxyisoprostanes EI (1) and EC (2) are effective inhibitors of the secretion of proinflammatory cytokines IL-6 and IL-12. In detailed studies toward the investigation of the molecular mode of action of these structures, a highly potent lactone (3) derived from 1 was identified. The known isoprostanoids 1 and 2 are most likely precursors of 3, the product of facile intramolecular reaction between the epoxide with the carboxylic acid in 2.
- Egger, Julian,Bretscher, Peter,Freigang, Stefan,Kopf, Manfred,Carreira, Erick M.
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p. 17382 - 17385
(2015/02/19)
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- Precise supramolecular control of selectivity in the Rh-catalyzed hydroformylation of terminal and internal alkenes
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In this study, we report a series of DIMPhos ligands L1-L3, bidentate phosphorus ligands equipped with an integral anion binding site (the DIM pocket). Coordination studies show that these ligands bind to a rhodium center in a bidentate fashion. Experiments under hydroformylation conditions confirm the formation of the mononuclear hydridobiscarbonyl rhodium complexes that are generally assumed to be active in hydroformylation. The metal complexes formed still strongly bind the anionic species in the binding site of the ligand, without affecting the metal coordination sphere. These bifunctional properties of DIMPhos are further demonstrated by the crystal structure of the rhodium complex with acetate anion bound in the binding site of the ligand. The catalytic studies demonstrate that substrate preorganization by binding in the DIM pocket of the ligand results in unprecedented selectivities in hydroformylation of terminal and internal alkenes functionalized with an anionic group. Remarkably, the selectivity controlling anionic group can be even 10 bonds away from the reactive double bond, demonstrating the potential of this supramolecular approach. Control experiments confirm the crucial role of the anion binding for the selectivity. DFT studies on the decisive intermediates reveal that the anion binding in the DIM pocket restricts the rotational freedom of the reactive double bound. As a consequence, the pathway to the undesired product is strongly hindered, whereas that for the desired product is lowered in energy. Detailed kinetic studies, together with the in situ spectroscopic measurements and isotope-labeling studies, support this mode of operation and reveal that these supramolecular systems follow enzymatic-type Michaelis-Menten kinetics, with competitive product inhibition.
- Dydio, Pawel,Detz, Remko J.,Reek, Joost N. H.
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supporting information
p. 10817 - 10828
(2013/08/23)
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- The enantioselective synthesis of tetracyclic methyllycaconitine analogues
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A new enantioselective synthesis of ABEF ring analogues of methyllycaconitine has been developed using a chiral cobalt(III) salen-catalyzed Diels-Alder reaction to form the B ring. Subsequent elaboration to form the A, E and F rings was achieved by sequential Dieckmann, Mannich and Wacker-type cyclizations to afford tetracyclic analogues in 97.5% ee.
- Sparrow, Kevin,Barker, David,Brimble, Margaret A.
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experimental part
p. 7989 - 7999
(2011/11/07)
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- Kinetic analysis of terminal and unactivated C-H bond oxyfunctionalization in fatty acid methyl esters by monooxygenase-based whole-cell biocatalysis
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The alkane monooxygenase AlkBGT from Pseudomonas putida GPo1 constitutes a versatile enzyme system for the ω-oxyfunctionalization of medium chain-length alkanes. In this study, recombinant Escherichia coli W3110 expressing alkBGT was investigated as whole-cell catalyst for the regioselective biooxidation of fatty acid methyl esters to terminal alcohols. The ω-functionalized products are of general economic interest, serving as building blocks for polymer synthesis. The whole-cell catalysts proved to functionalize fatty acid methyl esters with a medium length alkyl chain specifically at the ω-position. The highest specific hydroxylation activity of 104 U gCDW-1 was obtained with nonanoic acid methyl ester as substrate using resting cells of E. coli W3110 (pBT10). In an optimized set-up, maximal 9-hydroxynonanoic acid methyl ester yields of 95% were achieved. For this specific substrate, apparent whole-cell kinetic parameters were determined with a Vmax of 204±9 U gCDW -1, a substrate uptake constant (KS) of 142±17 μM, and a specificity constant Vmax/KS of 1.4 U g CDW-1 μM-1 for the formation of the terminal alcohol. The same E. coli strain carrying additional alk genes showed a different substrate selectivity. A comparison of biocatalysis with whole cells and enriched enzyme preparations showed that both substrate availability and enzyme specificity control the efficiency of the whole-cell bioconversion of the longer and more hydrophobic substrate dodecanoic acid methyl ester. The efficient coupling of redox cofactor oxidation and product formation, as determined in vitro, combined with the high in vivo activities make E. coli W3110 (pBT10) a promising biocatalyst for the preparative synthesis of terminally functionalized fatty acid methyl esters. Copyright
- Schrewe, Manfred,Magnusson, Anders O.,Willrodt, Christian,Buehler, Bruno,Schmid, Andreas
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experimental part
p. 3485 - 3495
(2012/03/26)
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- Remote supramolecular control of catalyst selectivity in the hydroformylation of alkenes
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In the pocket: The supramolecular interactions between a Rh phosphine catalyst equipped with an anion-binding pocket and alkenes that contain anionic functionalities (see picture) provide an excellent design concept to achieve remote control of the regioselectivity in hydroformylation reactions. The 4-pentenoate and 3-butenylphosphonate, which fit tightly between the Rh center and the pocket, were hydroformylated with unprecedented selectivity.
- Dydio, Pawea,Dzik, Wojciech I.,Lutz, Martin,De-Bruin, Bas,Reek, Joost N. H.
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supporting information; experimental part
p. 396 - 400
(2011/03/16)
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- Synthesis of 2-normisoprostol, methyl6-(3-hydroxy-2-((E)-4-hydroxy-4- methyloct-1-enyl)-5-oxocyclopentyl)hexanoate
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Synthesis of 2-normisoprostol, methyl 6-(3-hydroxy-2-((E)-4-hydroxy-4- methyloct-1-enyl)-5-oxocyclopentyl)hexanoate (3), employing two-component coupling strategy based on 1,4-addition followed by DDQ-mediated triethyl silyl deprotection is reported. Desired key intermediates, methyl 6-(3-triethyl silyloxy-5-oxocyclopent-1-enyl)hexanoate (4) and (E)-1-(tributylstannyl)-4- methyloct-1-en-4-yloxy)triethylsilane (5), were prepared from commercially available cycloheptanone and propargyl bromide, and the intermediates were coupled to obtain 3 in a convergent approach.
- Harikrishna,Mohan, H. Rama,Dubey,Subbaraju, Gottumukkala V.
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experimental part
p. 2763 - 2775
(2009/12/06)
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- The conjugate addition-Peterson olefination reaction for the preparation of cross-conjugated cyclopentenone, PPAR-γ ligands
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5-Alkylidenecyclopent-2-enones 15a-q may be prepared via a conjugate addition-Peterson olefination sequence, best achieved in one-pot, using exo-2-trimethylsilyl-3a,4,7,7a-tetrahydro-4,7-methanoinden-1-one 12, followed by a retro-Diels-Alder reaction. The geometry of the exocyclic alkene may be controlled according to the use of organometallic species in the conjugate addition step; organocuprate reagents are found to selectively lead to the formation of E-exocyclic alkene adducts, whereas Grignard reagents favour the formation of Z-alkenyl isomers. The use of enantiomerically enriched 12, accessed from an asymmetric Pauson-Khand reaction, affords the corresponding enantioenriched 5-alkylidenecyclopent-2-enones and this approach is exemplified by the short, stereoselective total syntheses of two cyclopentenone phytoprostanes 51 and 13,14-dehydrophytoprostane J165. The ability of this family of synthetic compounds to activate the peroxisome proliferator activated receptor-γ is reported.
- Iqbal, Mazhar,Duffy, Patricia,Evans, Paul,Cloughley, George,Allan, Bernard,Lledo, Agusti,Verdaguer, Xavier,Riera, Antoni
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supporting information; experimental part
p. 4649 - 4661
(2009/03/12)
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- Structure-activity relationship study of flowering-inducer FN against Lemna paucicostata
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FN1 (1) and FN2 (2), cycloadducts of α-ketol octadecadienoic acid (3) with norepinephrine (NE), induce flowering in Lemna paucicostata. In order to broaden our understanding of structural requirements of FN?for flower induction, nine analogs of 3 (4-12) were synthesized and reacted with NE under basic conditions. These analogs, except for 8, 10, and 12, exhibited significant activity regarding to floral induction in L. paucicostata. Similar experiments were carried out by using 3 and epinephrine, and it was demonstrated that these products also possessed biological activity.
- Kai, Kenji,Takeuchi, Jun,Kataoka, Taichi,Yokoyama, Mineyuki,Watanabe, Naoharu
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p. 6760 - 6769
(2008/12/21)
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- Total synthesis of azumamide A and azumamide E, evaluation as histone deacetylase inhibitors, and design of a more potent analogue
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(Chemical Equation Presented) The unprecedented diastereoselective Mannich reaction of a Z-allylsulfoximine was a key step in the total synthesis of the marine natural products azumamide A and E, and an unnatural analogue. Their relative potency as histone deacetylase inhibitors was evaluated and found to correlate with predicted zinc-binding affinity.
- Wen, Shijun,Carey, Krystle L.,Nakao, Yoichi,Fusetani, Nobuhiro,Packham, Graham,Ganesan
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p. 1105 - 1108
(2007/10/03)
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- Surveying approaches to the formation of carbon-carbon bonds between a pyran and an adjacent ring
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We have examined several methods for the stereoselective formation of carbon-carbon bonds between contiguous rings where a stereogenic center is already present. The approaches investigated were a [1,3] oxygen to carbon rearrangement of cyclic vinyl acetals, an intermolecular enolsilane addition into an in situ generated oxocarbenium ion, an intramolecular conjugate addition of tethered alkoxy enones, and epimerization of several α-pyranyl cycloalkanones. These routes have been found to be complementary in several cases and have enabled formation of both the trans:anti and cis:anti stereoisomers in good to excellent yields and varying diastereoselectivities. We have proven C2-C2′ relative stereochemistry of 1-2 via a chemical correlation.
- Frein, Jeffrey D.,Rovis, Tomislav
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p. 4573 - 4583
(2007/10/03)
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- Conversion of (Z)-1,4-dihydroxyalk-2-enes into 2,5-dihydrofurans and of alkane-1,4-diols into tetrahydrofurans via acid-catalysed cyclisation of the monoisoureas formed by their copper(I)-mediated reactions with dicyclohexylcarbodiimide
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(Z)-1,4-dihydroxyalk-2-enes were converted into 2,5-dihydrofurans and alkane-1,4-diols were converted into tetrahydrofurans via acid-catalysed cyclisation of the monoisoureas. The reaction involved protonation of the carbodiimide by acidic phenol followed by reaction with alkanol. Pd/CaCo3-quinoline catalyst system was employed in the presence of a little triethylamine to overcome partial hydrogenolysis.
- Duffy, Michael G.,Grayson, David H.
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p. 1555 - 1563
(2007/10/03)
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- Photo-cleavage of carbon-carbon bond of α-iodocycloalkanones giving ω,ω-dialkoxyalkanoic ester in alcohol
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The irradiation at λ > 300 nm of α-iodocycloalkanones with a high- pressure mercury lamp in alcohols containing a small amount of water afforded the corresponding ω,ω-dialkoxyalkanoic ester (65-88%) by photochemical cleavage of the C(I)-C=O bond at room temperature. In the case of a commercial fluorescent lamp as the irradiating light source, photochemical ring-opening products were also obtained. The irradiation of 2α-iodo-5α- and 4β-iodo-5β-cholestan-3-ones in methanol gave methyl 2,2-dimethoxy-2,3- seco-5α-cholestan-3-oate and methyl 4,4-dimethoxy-3,4-seco-5β-cholestan-3- oate in 78 and 62% yields, respectively. The photochemical behavior of the cleavage reaction of α-iodocycloalkanones is also discussed on the basis of 2-hydroxycycloalkanone as an intermediate.
- Ji, Shun-Jun,Horiuchi, C. Akira
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p. 1645 - 1652
(2007/10/03)
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- Oxidation of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate in alcohols and acetic acid
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The reaction of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate (CS) in alcohols and acetic acid gave the corresponding alkyl esters of oxo acids (80-96%) and oxo acids (78-96%), respectively, by oxidative cleavage of the C(R).C=O bond. In the case of 2-iodocycloalkanones in methanol, the dimethyl ester was obtained in good yield. A treatment of 5α-cholestan-3-one with CS in methanol produced 2-acetal 3-ester of 2,3-seco derivative in good yield. The effects of cerium(IV) and copper(II) salts are also discussed.
- He, Liangyou,Horiuchi, C. Akira
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p. 2515 - 2521
(2007/10/03)
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- PhI(OAc)2-Promoted Rearrangement of the Hydroxyl Group: Ring Expansion of 4-Hydroxy-2-cyclobutenone to 2(5H)-Furanone in Comparison with Ring Cleavage of the α-Hydroxycycloalkanone to the ω-Formyl Ester
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Reaction of 4-hydroxy-2-cyclobutenones with PhI(OAc)2 in 1,2-dichloroethane at reflux temperature gave rise to 5-acetoxy-2(5H)-furanones as a rearranged product, formation of which is explained by ring cleavage of the once formed hypervalent iodine intermediate and following recyclization of the resulting acyl cation with a carbonyl oxygen. Likewise, 5-methoxy-2(5H)-furanones were obtained in better yields by using methanol as both a solvent and a nucleophile. Extension of this reaction to simple 2-hydroxycycloalkanones resulted in ring cleavage to methyl ω-formylalkanoates under milder conditions. In this case, the mechanism is explained by known glycol cleavage with PhI-(OAc)2.
- Ohno, Masatomi,Oguri, Isamu,Eguchi, Shoji
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p. 8995 - 9000
(2007/10/03)
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- Reductive Cyclization of Ketones Tethered to Activated Olefins Mediated by Magnesium in Methanol
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The reductive cyclization of various ketones tethered to activated olefins such as α,β-unsaturated esters, nitriles, sulfoxides, and sulfides mediated by magnesium in dry methanol in the presence of mercuric chloride.When traeted with magnesium in dry methanol at -23 deg C all of the ketones except nitrile 9 (42percent) and 5-oxa-8-keto-2-enoate 5 (13percent) gave excellent yields (79-98percent) of mono- and bicyclic alcohol products resulting from carbon-carbon bond formation between the β-carbon of the activated olefin and the carbonyl carbon.The reaction was accelerated by the catalytic amount of mercuric chloride, although the stereoselectivity was not affected by the catalyst.For all the substrates except 8-keto-2-enoate 3 and 5-aza-8-keto-2-enoate 6, the configuration of the major product was trans between the hydroxy and (methoxycarbonyl)methyl groups.The product isomer ratios were independent of the substrate geometry (E or Z).In contrast to the ketones, aldehydes tethered to α,β-unsaturated esters gave products of simple reduction of the double bond and/or saturated alcohols instead of the cyclized products.When the reaction temperature was lowered, the yields of cyclized product were significantly affected by the production of appreciable amounts of saturated product, but the stereoselectivity was not improved.Under the same reaction conditions α,β-unsaturated sulfoxide 16 gave deoxygenated sulfide 18 (85percent) as the major product along with a small amount (9percent) of cyclized product 19t.In contrast, sulfone 17 underwent desulfonylation instead of cyclization to give olefin 20 (54percent).With excess magnesium (15 equiv), however, α,β-unsaturated sulfoxide 16 gave cyclized sulfide 19t (95percent) via deoxygenated sulfide 18.Both 16Z and 16E afforded product 19t as a single isomer.It is suggested that the reductive cyclization of the α,β-unsaturated esters and nitriles proceed by means of nucleophilic attack of a β-carbon radical anion, formed by initial electron transfer from magnesium metal to the activated olefin, on the carbonyl group.The cyclization of the α,β-unsaturated sulfide proceeds by nucleophilic attack of the ketyl on the olefinic double bond.
- Lee, Ge Hyeong,Choi, Eun Bok,Lee, Eun,Pak, Chwang Siek
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p. 1428 - 1443
(2007/10/02)
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- Amberlyst A 21 as new and efficient surface catalyst for the cleavage of 2-nitrocycloalkanones
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Ring cleavage of 2-Nitrocycloalkanones with methanol/Amberlyst A 21 gave methyl ω-nitroalkanoates, O2NCH2(CH2)(n)CO2Me where n = 3-6, 8-10,13, in high yield. Subsequent Nef reaction gave the corresponding ω-oxo compounds which were isolated, in the case of methyl 7-oxoheptanoate and methyl 8-oxooctanoate only, or reduced directly with sodium borohydride to give ω-hydroxyalkanoates. A new formal synthesis of exaltolide (15-pentadecanolide) is also reported.
- Ballini,Petrini,Polzonetti
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p. 355 - 357
(2007/10/02)
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- Novel methods for the construction of 3-(2H) furanone spiroketals
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Two stereoselective routes to the 3-(2H) furanone spiroketal 1 have been achieved.
- Linderman, Russell J.,Viviani, Fabrice G.,Kwochka, William R.
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p. 3571 - 3574
(2007/10/02)
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- An improved and simple synthesis of methyl or ethyl 7-oxoheptanoate and 7-acetoxyheptanal
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Reaction of cycloheptanone with potassium persulfate, in ethanol or methanol, gave ethyl or methyl 7-hydroxyheptanoate which, by oxidation with PCC, were converted into ethyl or methyl 7-oxoheptanoate in good yields. Protection of aldehyde group of methyl 7-oxoheptanoate, followed by one-step conversion of carboxylic ester to the acetate gave, after regeneration of aldehyde group, 7-acetoxyheptanal.
- Ballini,Marcantoni,Petrini
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p. 1075 - 1081
(2007/10/02)
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- SYNTHESIS OF PHEROMONES, IV. CHEMISTRY OF THE WITTIG REACTION, I. EFFECTS OF REACTION CONDITIONS ON THE STEREOSELECTIVITY AND YIELD OF THE WITTIG REACTION
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The reactions of nonstabilized triphenylphosphorus ylides with aldehydes have been studied in detail.The stereochemistry and yields of the alkene products are highly dependent upon base used for the generation of the ylide, the solvent and reaction temperature.The synthesis of sex pheromone components by Wittig reaction are also described.
- Vinczer, Peter,Juvancz, Zoltan,Novak, Lajos,Szantay, Csaba
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p. 797 - 820
(2007/10/02)
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- The Capsaicinoids: Their Separation, Synthesis, and Mutagenicity
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Capsaicin (1b), the pungent ingredient in many varietes of Capsicums has recently been implicated as a possible carcinogen.When obtained from natural sources 1b is always accompanied by a number of related homologues.We have isolated seven of these homologues, characterized them, and synthesized them by a general and unique route developed in our laboratories.Also reported are mutagenicity data for 1b and an extract of red pepper as measured by the Ames assay and the V-79 mammalian cell assay.
- Gannett, Peter M.,Nagel, Donald L.,Reilly, Pam J.,Lawson, Terence,Sharpe, Jody,Toth, Bela
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p. 1064 - 1071
(2007/10/02)
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- A Mass Spectroscopic Study of Dimethyl Ester Trimethyl Ether Derivatives of Some 3-Hydroxydicarboxylic Acids
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The fragmentation pathways for the dimethyl ester trimethylsilyl ether derivatives of some 3-hydroxydicarboxylic acids have been found by using B/E and B2/E linked scans and isotope substitution techniques.Most of the fragments are due to ionization at silicon, which induces a fragmentation pattern that intimately reflects the structure of the compounds.
- Svendsen, John S.,Sydnes, Leiv K.,Whist, Jon E.
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p. 421 - 429
(2007/10/02)
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- OZONOLYTIC CLEAVAGE OF CYCLOALKENES TO TERMINALLY DIFFERENTIATED PRODUCTS
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Conditions are reported which convert cycloalkenes to terminally differentiated product through the intermediacy of α-alkoxy hydroperoxides.
- Schreiber, Stuart L.,Claus, Ronald E.,Reagan, Jeff
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p. 3867 - 3870
(2007/10/02)
-
