- Stereospecific synthesis of all four isomeric 6,8-heneicosadien-11-ones: Sex pheromone components of the painted apple moth Teia anartoides
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All four isomeric 6,8-heneicosadien-11-ones were synthesised using a Suzuki-coupling strategy.
- Comeskey, Daniel J.,Bunn, Barry J.,Fielder, Simon
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- Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds
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The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were explored. A highly Lewis acidic boron reagent and electron-withdrawing ligand system were required to form the pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl-trihydroborate, gave a THF stabilised phosphoranyl-borane intermediate upon a single hydride abstraction in THF. This compound could undergo a unique rearrangement, which involved a two-fold ring expansion, to give a fused bicyclic compound or it could act as a mono-hydroboration reagent. The hydroboration reactivity of the intermediate was found to be higher towards alkynes vs. alkenes, with good to moderate regioselectivity towards the terminal carbon. The second compound, a phosphoranyl-triarylborate, was found to have different reactivity as it was highly stable towards acids and bases. This is thought to be due to the large bulk around the P–B bond as shown in the crystal structure.
- Havare, Nizam,Kano, Naokazu,Morokuma, Keiji,O'Brien, Nathan J.,Ramozzi, Romain,Uematsu, Ryohei
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- Synthesis and biological evaluation of 6,7-disubstituted 4-aminopyrido[2,3-d]pyrimidines as adenosine kinase inhibitors
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The synthesis and structure-activity relationship of a series of 6,7-disubstituted 4-aminopyrido[2,3-d]pyrimidines as novel non-nucleoside adenosine kinase inhibitors is described. A variety of substituents, primarily aryl, at the C6 and C7 positions of the pyridopyrimidine core were found to yield analogues that are potent inhibitors of adenosine kinase. In contrast to the 5,7-disubstituted and 5,6,7-trisubstituted pyridopyrimidine series, these analogues exhibited only modest potency to inhibit AK in intact cells.
- Perner, Richard J.,Lee, Chih-Hung,Jiang, Meiqun,Gu, Yu-Gui,DiDomenico, Stanley,Bayburt, Erol K.,Alexander, Karen M.,Kohlhaas, Kathy L.,Jarvis, Michael F.,Kowaluk, Elizabeth L.,Bhagwat, Shripad S.
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p. 2803 - 2807
(2007/10/03)
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- A photochemical entry to depsides: Synthesis of gustastatin
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(Chemical Equation Presented) Herein, we propose a modular and general strategy to construct orcinol-type depsides based on the photolysis of functionalized benzodioxinones (I). Notably, resorcinylic esters are obtained without competing isocoumarin (II) formation, exemplified by the first total synthesis of gustastatin in 10 steps from commercially available trihydroxybenzoic acid.
- Garcia-Fortanet, Jorge,Debergh, John R.,De Brabander, Jef K.
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p. 685 - 688
(2007/10/03)
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- 2-Pyrones possessing antimicrobial and cytotoxic activities
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The 2-pyrone sub-unit is found in a number of natural products possessing broad spectrum biological activity. Such compounds are validated as being capable of binding to specific protein domains and able to exert a remarkable range of biological effects. In an effort to identify synthetic 2-pyrones with interesting biological effects, herein we report the synthesis and biological evaluation of 4-substituted-6-methyl-2-pyrones. Synthetic routes to 4-alkyl/alkenyl/aryl/alkynyl-6-methyl-2-pyrones have been developed utilising Sonogashira, Suzuki and Negishi cross-coupling starting from readily available 4-bromo-6-methyl-2-pyrone. Specific conditions for each organometallic protocol were required for successful cross-coupling. In particular, a triethylamine/acetonitrile - base/solvent mixture was crucial to Sonogashira alkynylation of 4-bromo-6-methyl-2-pyrone, whereas thallium carbonate was a mandatory base for the Suzuki cross-coupling of trialkylboranes. The 2-pyrones demonstrate potent inhibitory activity against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Schizosaccharomyces pombe and Botrytis cinerea. The growth inhibitory activities of selected 2-pyrones were determined in A2780 human ovarian carcinoma and K562 human chronic myelogenous leukaemia cell lines using an in vitro cell culture system (MTT assay). These studies demonstrate that 4-phenylethynyl-, 4-tetrahydropyranylpropargyl ether- and 4-ethynyl-6-methyl-2-pyrones have excellent potential as a new class of anticancer agents.
- Fairlamb, Ian J. S.,Marrison, Lester R.,Dickinson, Julia M.,Lu, Feng-Ju,Schmidt, Jan Peter
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p. 4285 - 4299
(2007/10/03)
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- Kinetic Enzymatic Resolution of Cyclopropane Derivatives
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The kinetic enzymatic resolution of various cyclopropane derivatives was systematically investigated. The study focused on synthetically useful cyclopropylmethanols (e.g., 18a/j or 19a/j) as well as some rarely investigated cyclopropanols (e.g., 24/25 or 27). The combination of enantioselective catalytic or diastereoselective synthesis of enantiomerically enriched compounds with enzymatic approaches ultimately led to the most convenient route to enantiomerically pure starting materials. Again, this was especially proven for the synthesis of cyclopropanols 18a/j and 19a/j. Key to the successful investigation was to rigorously establish an analytical tool for the analysis of enantiomeric composition of reaction mixtures.
- Pietruszka, Joerg,Rieche, Anja C. M.,Wilhelm, Thorsten,Witt, Andreas
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p. 1273 - 1286
(2007/10/03)
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- Preparation, properties, and synthetic potentials of novel boronates in a fluorous version (fluorous boronates)
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(equation presented) 4a-j R = aryl, alkenyl, alkyl A series of boronic acids were attached to a fluorous tag by esterification. Functional transformations of these boronates together with the fluorous Suzuki coupling reaction illustrated their usefulness in fluorous-phase techniques.
- Chen, Dajun,Qing, Feng-Ling,Huang, Yangen
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p. 1003 - 1005
(2007/10/03)
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- Synthesis of enantiomerically pure cyclopropanes from cyclopropylboronic acids
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A general method for the stereocontrolled synthesis of cyclopropanes is described. Various, highly stable, enantiomerically pure alkenylboronic esters 13 have been conveniently synthesized by the direct hydroboration of alkynes 11 using the new chiral 1,3,2-dioxaborolane 15. The high stability was also demonstrated by the selective deprotection of a tert- butyldimethylsilyl protecting group without hydrolyzing the boronic ester. The diastereoselective cyclopropanation of the olefins was achieved by the palladium(II) acetate catalyzed decomposition of diazomethane. This process was optimized giving cyclopropylboronic esters 20/21 in high yield (89-99%) and with good to excellent diastereomeric ratios (up to 95:5). The diastereomers were separated by means of MPLC and their configurations determined by X-ray crystallography (compound 21c), by transformation to known cyclopropanols, and by correlation of NMR data. Treatment with LiAlH4 followed by acidic hydrolysis yielded the enantiomerically pure cyclopropylboronic acid 27 for the first time and allowed the nearly quantitative recovery of the chiral auxiliary 3. Different protocols for the Suzuki coupling reaction of compound 27 were investigated.
- Luithle, Joachim E.A.,Pietruszka, Joì?rg
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p. 8287 - 8297
(2007/10/03)
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- Coupling reaction of 4-cyclopentene-1,3-diol monoacetate and lithium alkenylborates and its application to chiral synthesis of prostaglandin intermediates
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Lithium alkenylborates couple with the monoacetate of 4-cyclopentene-1,3-diol under the nickel catalyst regioselectively and stereospecifically to afford trans 1,3-isomers in good yields. Moreover, an unexpectedly high level of regio-selectivity is observ
- Usmani, Shahid B.,Takahisa, Eisuke,Kobayashi, Yuichi
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p. 601 - 604
(2007/10/03)
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- Organoboranes. 30. Convenient procedures for the synthesis of alkyl- and alkenylboronic acids and esters
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Alkyl- and alkenyldibromoborane-dimethyl sulfide complexes, readily obtained by the hydroboration of alkenes and alkynes with dibromoborane-dimethyl sulfide (HBBr2-SMe2), react with water, giving the corresponding boronic acids, and with alcohols and glycols to give the corresponding esters. Various procedures have been developed for the preparation of boronic esters with primary and secondary alcohols, glycols, and tertiary alcohols. Boronic acids react with primary and secondary alcohols reversibly to form the corresponding esters. The equilibrium may be conveniently displaced in favor of ester by carrying out the reaction in pentane, from which the water component separates. This procedure does away with the necessity of azeotrope distillation of a ternary mixture, extensively used previously for the esterification of boronic acids.
- Brown, Herbert C.,Bhat,Somayaji, Vishwanatha
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p. 1311 - 1316
(2008/10/08)
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- Lithium bis(ethylenedioxyboryl)methide and its reactions with carbonyl compounds and with the chlorotriphenyl derivatives of germanium, tin and lead
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Transesterification of tris(dimethoxyboryl)methane, HC[B(OCH3)2]3, with ethylene glycol yielded tris(ethylenedioxyboryl)methane (I), HC(BO2C2H4)3 which with methyllithium in THF at -70°C precipitated lithium bis(ethylenedioxyboryl)methide (II), Li+ HC(BO2C2H4)2-. Reaction of II with Ph3MCl, where M = Ge, Sn, or Pb, gave Ph3MCH(BO2C2H4)2. The analogous 1,3-propanediol ester, Li+HC(BO2C3H6)2-, yielded Ph3MCH(BO2C3H6)2. Treatment of Ph3SnCH(BO2C2H4)2 with MeLi followed by Ph3SnCl gave (Ph3Sn)2CHBO2C2H4, showing that one B and one Sn atom are sufficient to stabilize a carbanion. Reaction of II with aldehydes gave high yields of 1-alkene-1-boronic esters, RCHCHBO2C2H4, with unexpectedly high stereoselectivity, 90-100% trans by NMR analysis. Aqueous work-up of these boronic esters yielded the boronic acids, RCHCHB (OH)2, which crystallized as the pure trans isomers. Ketones react with II in an analogous manner. The reaction with acetophenone was not stereospecific. Functional group compatibility has been demonstrated in condensations of II with 1,3-dichloroacetone, cinnamaldehyde, p-nitrobenzaldehyde, and p-dimethylaminobenzaldehyde. The trans geometry of the major isomer of CH3CHCHBO2C2H4 was proved by B-butylation with butyllithium followed by rearrangement with iodine and base to form cis-2-heptene, a sequence of known stereochemistry, and analogous structure proofs were carried out with cis-CH3CHCHBO2C2H4 and trans-C6H5CHCHBO2C2H4.
- Matteson, Donald S.,Jesthi, Pradipta K.
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