- Enzyme-Mediated Directional Transport of a Small-Molecule Walker with Chemically Identical Feet
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We describe a small-molecule "walker" that uses enzyme catalysis to discriminate between the relative positions of its "feet" on a track and thereby move with net directionality. The bipedal walker has identical carboxylic acid feet, and "steps" along an isotactic hydroxyl-group-derivatized polyether track by the formation/breakage of ester linkages. Lipase AS catalyzes the selective hydrolysis of the rear foot of macrocyclized walkers (an information ratchet mechanism), the rear foot producing an (R)-stereocenter at its point of attachment to the track. If the hydrolyzed foot reattaches to the track in front of the bound foot it forms an (S)-stereocenter, which is resistant to enzymatic hydrolysis. Only macrocyclic walker-track conjugates are efficiently hydrolyzed by the enzyme, leading to high processivity of the walker movement along the track. Conventional chemical reagents promote formation of the ester bonds between the walker and the track. Iterative macrocyclization and hydrolysis reactions lead to 68% of walkers taking two steps directionally along a three-foothold track.
- Martin, Christopher J.,Lee, Alan T. L.,Adams, Ralph W.,Leigh, David A.
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Read Online
- GLYCOSIDE COMPOUND AND PREPARATION METHOD THEREFOR, COMPOSITION, APPLICATION, AND INTERMEDIATE
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The present invention discloses a glycoside compound represented by Formula III, and a preparation method, a composition, use and an intermediate thereof. The glycoside compound provided in the present invention has simple preparation method, can significantly increase the expression of VEGF-A mRNA, and is effective in promoting the angiogenesis. This provides a reliable guarantee for the development of drugs with pro-angiogenic activity for treating cerebral infarction cerebral stroke, myocardial infarction, and ischemic microcirculatory disturbance of lower limbs.
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Paragraph 0358; 0361
(2021/04/23)
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- NUCLEOSIDE PRODRUGS AND USES RELATED THERETO
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Disclosed are acyclic nucleoside prodrugs with improved metabolic stability and oral bioavailability. In general, the prodrugs are derivatives of acyclic nucleoside phosphonates containing a lipid-like moiety that can increase oral absorption and subsequent stability in the liver and plasma. Preferably, the lipid-like moiety can resist enzyme-mediated ω-oxidation, such as ω -oxidation catalyzed by cytochrome P450 enzymes. Also disclosed are pharmaceutical formulations of the acyclic nucleoside prodrugs. The acyclic nucleoside prodrugs and pharmaceutical formulations thereof can be used to treat viral infections, such as HIV infections, and/or viral-associated cancer, such as HPV-associated cancers.
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Page/Page column 207; 208
(2021/02/26)
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- Iron-catalysed enantioconvergent Suzuki-Miyaura cross-coupling to afford enantioenriched 1,1-diarylalkanes
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The first stereoconvergent Suzuki-Miyaura cross-coupling reaction was developed to afford enantioenriched 1,1-diarylalkanes. An iron-based complex containing a chiral cyanobis(oxazoline) ligand framework was best to obtain enantioenriched 1,1-diarylalkanes from cross-coupling reactions between unactivated aryl boronic esters and benzylic chlorides. Enhanced yields were obtained when 1,3,5-trimethoxybenzene was used as an additive, which is hypothesized to extend the lifetime of the iron-based catalyst. Exceptional enantioselectivities were obtained with challenging ortho-substituted benzylic chlorides. This journal is
- Tyrol, Chet C.,Yone, Nang S.,Gallin, Connor F.,Byers, Jeffery A.
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supporting information
p. 14661 - 14664
(2020/12/02)
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- Compound as well as preparation method and medical application thereof
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The invention provides a compound as well as a preparation method and medical application thereof, the compound has a structure as shown in a general formula (I), and can also be a tautomer, a mesomer, a raceme, an enantiomer, a diastereoisomer, or a mixture form thereof, or a pharmaceutically acceptable salt thereof. According to the compound with the structure as shown in the general formula (I)provided by the invention, a specific main chain structure and a corresponding substituent group are selected, so that the obtained compound can be used as an arginase inhibitor, is relatively high in activity, and has a potential treatment prospect in various diseases.
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Paragraph 0252-0255
(2020/02/14)
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- Progress toward the total synthesis of mirabalin isomers
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Key fragments of the cytotoxic marine macrolide mirabalin have been synthesized, by using a flexible strategy based on asymmetric reductions to control the hydroxy- and carbamate-bearing stereocenters. In particular, ruthenium or rhodium-mediated asymmetric hydrogenation and transfer hydrogenation were used in combination with a dynamic kinetic resolution to control two contiguous stereocenters in a single step.
- Echeverria, Pierre-Georges,Pons, Amandine,Prévost, Sébastien,Férard, Charlène,Cornil, Johan,Guérinot, Amandine,Cossy, Janine,Phansavath, Phannarath,Ratovelomanana-Vidal, Virginie
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- A short convergent synthesis of the [3.2.1]dioxabicyclooctane subunit of sorangicin A via regioselective epoxide opening
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In this paper, we disclose the synthesis of the dioxabicyclo[3.2.1]octane subunit of the potent antibiotic sorangicin A. The synthesis was achieved in a convergent manner in 8 steps. Regio- and stereoselective intermolecular epoxide opening, ring-closing metathesis and iodo-etherification are key steps. cis-2-Butene diol has been employed as a common staring material.
- Raghavan, Sadagopan,Nyalata, Satyanarayana
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supporting information
p. 1071 - 1077
(2018/02/10)
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- Organocatalytic Enantioselective 1,3-Difunctionalizations of Morita-Baylis-Hillman Carbonates
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The in-situ-generated zwitterionic allylic ylides between Morita-Baylis-Hillman carbonates from isatins and chiral tertiary amine catalysts underwent highly regioselective and enantioselective 1,3-oxo-ethynylation or 1,3-amino-sulfenylation reactions with silyl ethynyl-1,2-benziodoxol-3(1H)-ones or N-(aryl or alkylthio)imides, respectively, giving densely functionalized products bearing a quaternary stereogenic center. An array of diversely structured scaffolds were efficiently constructed from the products, showing the synthetic versatility of the current catalytic strategy.
- Chen, Zhi-Chao,Chen, Peng,Chen, Zhi,Ouyang, Qin,Liang, Hua-Ping,Du, Wei,Chen, Ying-Chun
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supporting information
p. 6279 - 6283
(2018/10/09)
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- Chitosan grafted with a heteropolyanion-based ionic liquid as an effective and reusable catalyst for acetalization
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Chitosan immobilized with an acidic ionic liquid (CS-VImPS-PW) was fabricated via a radical addition reaction of N-vinylimidazoliumpropane sulfonate and chitosan, followed by acidification with a heteropolyacid. It was characterized by a Fourier transform infrared spectrometer, solid-state 13C nuclear magnetic resonance spectrometer, thermogravimetric analyzer, elemental analyzer, and Hammett indicator. Some acetalization reactions were investigated to evaluate the catalytic activity of CS-VImPS-PW. The results show that CS-VImPS-PW is highly active for the acetalization reactions in high acetal yields ranging from 83.2 to 96.2% and can be reused 8 times without noticeable loss of activity.
- Zhang, Wei-Hong,Liu, Shan-Shan,Liu, Ping,Xu, Jie,Xue, Bing,Wei, Xian-Yong,Li, Yong-Xin
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p. 41404 - 41409
(2016/05/19)
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- Copper-Catalyzed Oxy-Alkynylation of Diazo Compounds with Hypervalent Iodine Reagents
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Alkynes have found widespread applications in synthetic chemistry, biology, and materials sciences. In recent years, methods based on electrophilic alkynylation with hypervalent iodine reagents have made acetylene synthesis more flexible and efficient, but they lead to the formation of one equivalent of an iodoarene as side-product. Herein, a more efficient strategy involving a copper-catalyzed oxy-alkynylation of diazo compounds with ethynylbenziodoxol(on)e (EBX) reagents is described, which proceeds with generation of nitrogen gas as the only waste. This reaction is remarkable for its broad scope in both EBX reagents and diazo compounds. In addition, vinyl diazo compounds gave enynes selectively as single geometric isomers. The functional groups introduced during the transformation served as easy handles to access useful building blocks for synthetic and medicinal chemistry.
- Hari, Durga Prasad,Waser, Jerome
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supporting information
p. 2190 - 2193
(2016/03/08)
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- Nickel-Catalyzed Asymmetric Kumada Cross-Coupling of Symmetric Cyclic Sulfates
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Nickel-catalyzed enantioselective cross-couplings between symmetric cyclic sulfates and aromatic Grignard reagents are described. These reactions are effective with a broad range of substituted cyclic sulfates and deliver products with asymmetric tertiary carbon centers. Mechanistic experiments point to a stereoinvertive SN2-like oxidative addition of a nickel complex to the electrophilic substrate.
- Eno, Meredith S.,Lu, Alexander,Morken, James P.
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supporting information
p. 7824 - 7827
(2016/07/11)
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- (Z)-Selective enol triflation of α-alkoxyacetoaldehydes: Application to synthesis of (Z)-allylic alcohols via cross-coupling reaction and [1,2]-wittig rearrangement
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The stereoselective transformation of α-alkoxyacetoaldehydes to the corresponding (Z)-vinyl triflates was achieved by treatment with phenyl triflimide and DBU. The stereochemistry was explained by the "syn-effect," which was attributed primarily to an σ → π interaction. The β-alkoxy vinyl triflates obtained were applied to the stereoselective synthesis of structurally diverse (Z)-allylic alcohols via transition metal-catalyzed cross-coupling reaction and [1,2]-Wittig rearrangement.
- Kurosawa, Fumiya,Nakano, Takeo,Soeta, Takahiro,Endo, Kohei,Ukaji, Yutaka
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p. 5696 - 5703
(2015/06/16)
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- Selective deprotection of benzyl (Bn) ethers in the presence of para-methoxybenzyl (PMB) ethers
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Substituted benzyl ethers have been widely used as readily manipulatable protecting groups for organic synthesis. It is known that electron-rich para-methoxybenzyl (PMB) ethers can be selectively deprotected over benzyl or other electron-poor benzyl ethers under oxidative conditions. In this presentation, we will describe an approach for selective deprotection of benzyl ethers in the presence of PMB ethers under reductive conditions. This new method should complement the existing strategies in the utilization of substituted benzyl ethers in organic synthesis, especially in carbohydrate synthesis.
- Li, Xiaohua,Saleh, Zachary,Egri, Brian,Hourani, Ali,Harding, Luke,Baryal, Kedar N.,Zhu, Jianglong
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p. 1420 - 1422
(2015/03/04)
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- Stereocontrolled synthesis of a Cn-Cn+7 building block ("eastern moiety") for the unnatural enantiomers of important polyol,polyene antibiotics based on a ring-closing metathesis and an aldol addition of a lactone enolate
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A stereocontrolled synthesis of epoxide 6, which represents the C n-Cn+7 or "eastern moiety" building block for the title compounds, has been realized in 19 steps. Our synthesis started from tetrabromoacetone 26 and afforded dibromotriene 33b in six steps. The latter was subjected to a ring-closing metathesis, which gave the dibromovinyl-substituted lactone 34 in high yield. A highly stereoselective conjugate addition/enolate aldolization sequence established the additional stereocenters with perfect selectivity. Epoxide 47b was reached in another eight steps, which included a C-SiMe2Pha€‰→a€‰C-OH oxidation in the presence of an acetal group. The final structure 6 was completed by hydrostannylation/brominolysis. A dibromovinyl-substituted unsaturated δ-lactone obtained by ring-closing metathesis underwent a highly diastereoselective silyl cuprate 1,4-addition/aldolization sequence. Tamao-Fleming oxidation transformed the silyl into a hydroxy group. Alkyne formation, hydrostannylation, and N-bromosuccinimidolysis converted the dibromovinyl into a trans-bromovinyl moiety. Copyright
- Kamptmann, Sonja B.,Brueckner, Reinhard
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supporting information
p. 6584 - 6600
(2013/11/06)
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- A very practical and selective method for PMB protection of alcohols
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A very simple, practical and efficient one-step heterogeneous protocol for the PMB protection of alcohols using Amberlyst-15 has been developed. The stability and hazard issues regarding PMBCl and PMBBr are totally avoided by directly using anisyl alcohol for the protection. Alcohols are protected in very good yields. The selective mono-PMB protection of diols as well as di-PMB protection of diols was achieved in good yields, along with the demonstration of recyclability of the catalyst.
- Chavan, Subhash P.,Harale, Kishor R.
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experimental part
p. 4683 - 4686
(2012/09/05)
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- SUBSTITUTED INDAZOLE DERIVATIVES ACTIVE AS KINASE INHIBITORS
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The present invention relates to substituted indazole compounds which modulate the activity of protein kinases and are therefore useful in treating diseases caused by degulated protein kinase activity, like cancer. The present invention also provides methods for preparing these compounds, pharmaceutical compositions comprising these compounds, and methods of treating diseases utilizing such these compounds or the pharmaceutical compositions containing them.
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Page/Page column 44
(2012/12/13)
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- Gold(I)-catalysed intramolecular hydroamination of α-quaternary alkynes: Synthetic studies towards spiroimine marine toxins
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Cyclic spiroimines form an essential component of the bioactive pharmacophore in a number of potent fast-acting marine biotoxins, including the pinnatoxins, gymnodimine and the spirolides. These present a significant challenge for the total synthesis of this class of natural products. A novel approach to these cyclic spiroimines based on metal-catalysed hydroamination of spiroaminoalkyne precursors is reported herein. Au(PPh3)SbF 6 was found to effect the formation of bench-stable 5,6- and 6,6-spiroimine systems in high yields, although the 7,6-analogue remained elusive. To the best of our knowledge these are the first reported examples of α-quaternary cyclic imines formed via alkyne hydroamination.
- Zhang, Yanchuan C.,Furkert, Daniel P.,Guéret, Stéphanie M.,Lombard, Fanny,Brimble, Margaret A.
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scheme or table
p. 4896 - 4898
(2011/10/05)
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- Pd-Catalyzed intramolecular oxyalkynylation of alkenes with hypervalent iodine
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(Figure presented) The first example of intramolecular oxyalkynylation of nonactivated alkenes using oxidative Pd chemistry is reported. Both phenol and aromatic or aliphatic acid derivatives could be used under operator-friendly conditions (room temperature, technical solvents, under air). The discovery of the superiority of benzlodoxolone-derlved hypervalent iodine reagent 3d as an alkyne transfer reagent further expands the rapidly increasing utility of hypervalent iodine reagents in catalysis and is expected to have important implications for other similar processes.
- Nicolal, Stefano,Erard, Stephane,Gonzalez, Davinla Fernandez,Waser, Jerome
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supporting information; experimental part
p. 384 - 387
(2010/03/04)
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- Ethynyl-1,2-benziodoxol-3(1H)-one (EBX): An exceptional reagent for the ethynylation of keto, cyano, and nitro esters
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Hot alkyne! The in situ generation of ethynyl-1,2-benziodoxol-3(1H)-one (EBX) from a silyl-protected reagent by using TBAF is reported. EBX displayed exceptional acetylene transfer ability onto stabilized enolates (see scheme), even at -78 □°C. The mild reaction conditions allowed the first ethynylation reactions of linear keto, cyano, and nitro esters in high yields to give all-carbon quaternary centers or non-natural amino acids after selective reduction of the nitro group.
- Gonzalez, Davinia Fernandez,Brand, Jonathan P.,Waser, Jerome
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supporting information; experimental part
p. 9457 - 9461
(2010/10/03)
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- Synthetic studies of incednine: synthesis of C1-C13 pentaenoic acid segment
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Stereoselective synthesis of the C1-C13 pentaenoic acid segment (4) of the novel antibiotic incednine (1) is described.
- Ohtani, Takashi,Kanda, Hiroshi,Misawa, Kensuke,Urakawa, Yoshifumi,Toshima, Kazunobu
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scheme or table
p. 2270 - 2273
(2009/08/07)
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- Direct alkynylation of indole and pyrrole heterocycles
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Chemical Equitation Presentation Easy does it: The unique properties of benziodoxolone alkynyl periodinane l and gold catalysts have allowed the development of a high yielding, operationally simple (room temperature, no dry sol-vents or inert conditions, commercially available catalyst) reaction for the introduction of silylacetylenes on a large range of indole and pyrrole heterocycles with a wide range of functional groups (see scheme).
- Brand, Jonathan P.,Charpentier, Julie,Waser, Jerome
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supporting information; experimental part
p. 9346 - 9349
(2010/03/30)
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- Synthesis of enantiopure bicyclic α,α-disubstituted spirolactams via asymmetric Birch reductive alkylation
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The synthesis of enantiopure bicyclic α,α-disubstituted spirolactams is described using a diastereoselective Birch reductive alkylation as the key step. Hydrogenation of the resultant alkylated cyclohexadienes followed by intramolecular cyclization provides access to enantiopure 8-azaspiro[5.6]dodecan-7-ones.
- Gueret, Stephanie M.,O'connor, Patrick D.,Brimble, Margaret A.
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supporting information; experimental part
p. 963 - 966
(2009/07/11)
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- OXAZOLE AND THIAZOLE DERIVATIVES AND THEIR USES
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A quaternary ammonium compound of formula (I) having M3 receptor antagonist activity; a composition comprising such a compound; the use of such a compound in therapy (such as asthma or COPD); and a method of treating a patient with such a compound.
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Page/Page column 27-28
(2008/12/08)
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- Solvolysis of benzyl alcohols and ethers in 1,2-diols and application to a deprotection of benzyl ether-type protecting groups
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Some kinds of benzyl alcohols and ethers react with 1,2-diols, such as ethylene glycol and propylene glycol, at 130-190°C to give 2-hydroxyethyl or 2-hydroxypropyl ethers. Application of this reaction to a deprotection of benzyl ether-type protecting groups, under neutral conditions, was also described. Copyright
- Miyake, Hideyoshi,Fujimura, Masahiro,Tsumura, Takatsugu,Sasaki, Mitsuru
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p. 778 - 779
(2007/10/03)
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- Structure-based design of isoquinoline-5-sulfonamide inhibitors of protein kinase B
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Structure-based drug design of novel isoquinoline-5-sulfonamide inhibitors of PKB as potential antitumour agents was investigated. Constrained pyrrolidine analogues that mimicked the bound conformation of linear prototypes were identified and investigated by co-crystal structure determinations with the related protein PKA. Detailed variation in the binding modes between inhibitors with similar overall conformations was observed. Potent PKB inhibitors from this series inhibited GSK3β phosphorylation in cellular assays, consistent with inhibition of PKB kinase activity in cells.
- Collins, Ian,Caldwell, John,Fonseca, Tatiana,Donald, Alastair,Bavetsias, Vassilios,Hunter, Lisa-Jane K.,Garrett, Michelle D.,Rowlands, Martin G.,Aherne, G. Wynne,Davies, Thomas G.,Berdini, Valerio,Woodhead, Steven J.,Davis, Deborah,Seavers, Lisa C. A.,Wyatt, Paul G.,Workman, Paul,McDonald, Edward
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p. 1255 - 1273
(2007/10/03)
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- Cyanation of alcohols with diethyl cyanophosphonate and 2,6-dimethyl-1,4-benzoquinone by a new type of oxidation-reduction condensation
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Cyanation of various alcohols by a new type of oxidation-reduction condensation is described. Primary alkyl diphenylphosphinites, 2,6-dimethyl-1,4-benzoquinone (DMBQ), and diethyl cyanophosphonate gave the corresponding nitriles in high yields. During the above experiment on cyanation of 4-phenylbutan-2-ol, the unexpected formation of a mixture of nitrile and isocyanide was observed. After careful examination of the reaction conditions, selective synthesis of isocyanides from secondary alcohols was successfully accomplished by the use of zinc oxide (ZnO) as an additive. Reaction of tertiary alcohols provided the corresponding isocyanides exclusively in the absence of an additive. Cyanation of optically active alcohols was tried in order to clarify the stereochemistry of this reaction, and the reaction was thus proved to proceed with the inversion of configuration.
- Masutani, Kouta,Minowa, Tomofumi,Hagiwara, Yoshiaki,Mukaiyama, Teruaki
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p. 1106 - 1117
(2007/10/03)
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- Synthesis of 13C-labeled γ-hydroxybutyrates for EPR studies with 4-hydroxybutyryl-CoA dehydratase
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4-Hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum catalyses the reversible dehydration of its substrate 4-hydroxybutyryl-CoA (4-HB-CoA) to crotonyl CoA. The enzyme contains one [4Fe-4S]2+ cluster and one flavin adenine dinucleotide (FAD) molecule per homotetramer. Incubation of the enzyme with its substrate under equilibrium conditions followed by freezing at 77 K induced the EPR-spectrum of a neutral flavin semiquinone (g = 2.005, linewidth 2.1 mT), while at 10 K additional signals were detected. In an attempt to characterize these signals, 4-HB-CoA molecules specifically labeled with 13C have been synthesized. This was achieved via 13C- labeled γ-butyrolactones, which were obtained from 13C-labeled bromoacetic acids by efficient synthetic routes. Incubation of the 13C-labeled 4-hydroxybutyrate-CoA molecules with 4-hydroxybutyryl-CoA dehydratase did not lead to marked broadening of the signals.
- Naeser, Ulrike,Pierik, Antonio J.,Scott, Richard,Cinkaya, Irfan,Buckel, Wolfgang,Golding, Bernard T.
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- Photoaffinity analogues of farnesyl pyrophosphate transferable by protein farnesyl transferase
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Farnesylation is a posttranslational lipid modification in which a 15-carbon farnesyl isoprenoid is linked via a thioether bond to specific cysteine residues of proteins in a reaction catalyzed by protein farnesyltransferase (FTase). We synthesized analogues (3-6) of farnesyl pyrophosphate (FPP) to probe the range of modifications possible to the FPP skeleton which allow for efficient transfer by FTase. Photoaffinity analogues of FPP (5, 6) were prepared by substituting perfluorophenyl azide functional groups for the ω-terminal isoprene of FPP. Substituted anilines replace the ω-terminal isoprene in analogues 3 and 4. Compounds 3-5 were prepared by reductive amination of the appropriate anilines with 8-oxogeranyl acetate, followed by ester hydrolysis, chlorination, and pyrophosphorylation. Additional substitution of three methylenes for the β-isoprene of FPP gave photoprobe 6 in nine steps. Preparation of the analogues required TiCl4-mediated imine formation prior to NaBH(OAc)3 reduction for anilines with a pKa 3PCl2 conversion of allylic alcohols 13-16 into corresponding chlorides 17-20. Analogues 3-6 are efficiently transferred to target N- dansyl-GCVLS peptide substrate by mammalian FTase. Comparison of analogue structures and kinetics of transfer to those of FPP reveals that ring fluorination and para substituents have little effect on the affinity of the analogue pyrophosphate for FTase and its transfer efficiency. These results are also supported with models of the analogue binding modes in the active site of FTase. The transferable azide photoprobe 5 photoinactivates FTase. Transferable analogues 5 and 6 allow the formation of appropriately posttranslationally modified photoreactive peptide probes of isoprene function.
- Chehade, Kareem A. H.,Kiegiel, Katarzyna,Isaacs, Richard J.,Pickett, Jennifer S.,Bowers, Katherine E.,Fierke, Carol A.,Andres, Douglas A.,Spielmann, H. Peter
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p. 8206 - 8219
(2007/10/03)
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- Azidohalogenobenzyl derivatives, sugar compounds and protection of hydroxy groups
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Azidohalogenobenzyl derivatives of the formula (I) STR1 wherein A is a halogen atom, B is a halogen atom or a hydrogen atom, and X is a group reactive with a hydroxy group, methods of protecting hydroxy group(s) using said derivatives, and sugar compounds wherein a hydrogen atom of at least one hydroxy group is substituted by an azidohalogenobenzyl group. According to the present invention, there are provided novel derivatives capable of introducing a group into a compound having hydroxy group(s), which group is useful as a stable hydroxy-protecting group even in solid phase synthesis for the purpose of the extension of sugar chain under continuous acidic conditions and of being removed under mild conditions; sugar compounds protected by using said derivatives; and methods of protecting hydroxy group(s) using said derivatives.
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- 4-Azido-3-chlorobenzyl Ether, New Protection for Hydroxy Functions
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The 4-azido-3-chlorobenzyl (Cl-Azb) group was readily introduced to hydroxy functions by the use of a crystalline reagent, 4-azido-3-chlorobenzyl bromide, which was prepared from commercially available 2-chloro-4-methylaniline in two steps. Cl-Azb ethers have improved acid stability as compared to the corresponding parent 4-azidobenzyl (Azb) ether. Cl-Azb ethers were stable to direct 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) oxidation, but were cleaved smoothly by DDQ oxidation after conversion to the corresponding iminophosphorane derivative.
- Egusa, Kenji,Fukase, Koichi,Kusumoto, Shoichi
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p. 675 - 676
(2007/10/03)
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- Synthesis of biologically active sialyl Lewis X mimetics
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The design and synthesis of two sialyl Lewis X (SLe(x)) mimetics are described. In the design of mimetic 1, an ethylene glycol linkage is used to bridge the fucose and galactose moiety, and a carboxymethyl group is placed in the 3-OH position of the galactose residue to provide the negative charge which is believed to be essential for binding to (E)-selectin. In the design of mimetic 2, a D-tartaric acid derivative is used to provide the trans-dihydroxyl groups originally from the glucosamine moiety for the linkage of the fucose and the carboxypentyl groups. At a concentration of 1.5 mM, 1 inhibits 50% of the binding of SLe(x) glycoconjugate to immobilized recombinant (E)-selectin, while 2 has an IC50 of 10 mM. Mimetic 1 is also found to be stable toward α-L-fucosidase. Results from the ROESY and COSY experiments indicate that compound 1 is conformationally flexible, which may explain its relatively weak activity compared to SLe(x) (IC50 = 0.8 mM).
- Huang,Wong
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p. 3100 - 3106
(2007/10/02)
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- Synthetic route for 14C-labeling of a bioactive lipid A analogue
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A synthetic route for 14C-labeling of a phosphonooxyethyl (PE) analogue of E. coli lipid A was established by cold experiments. The PE analogue is chemically more stable than natural lipid A but shows particularly identical biological activity. The glycosidation of ethylene glycol unit as the 14C-labeled position was effected with a disaccharide thioglycoside by use of a hypervalent iodine reagent, PhIO-SnClO4-AgClO4, as an activator. p-Methoxybenzyl group used for the protection of the distal hydroxyl group of ethylene glycol was selectively removed by trimethylsilyl triflate in CH3CN-CH2Cl2 followed by phosphorylation and deprotection gave the target compound.
- Fukase,Aoki,Kinoshita,Suda,Kurosawa,Zahringer,Rietschel,Kusumoto
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p. 8645 - 8648
(2007/10/02)
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- REDUCTION OF ACETALS WITH CpTiCl3-LiAlH4
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The reduction of cyclic acetals and ketals derived from aromatic or aliphatic aldehydes and ketones with CpTiCl3-LiAlH4 system in diethyl ether at 30 deg C affords the corresponding hydroxyethyl ethers and the corresponding alkyl benzene or aliphatic hydrocarbons.
- Shaozu, Wu,Yin, Chen,Yulan, Zhang
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p. 421 - 424
(2007/10/02)
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- A efficient method for the reductive cleavage of aromatic acetals with ZrCl4-LiAlH4
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In our survey of the chemistry of ZrCl4-LiAlH4, we have found that acetals can be reduced to the corresponding ethers.We have explored the reductive condition and studied the reductive cleavage of different-membered cyclic acetals
- Shaozu, Wu,Yulan, Zhang,Tianhui, Ren
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p. 445 - 447
(2007/10/02)
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- 4-NITROBENZYL GROUP FOR PROTECTION OF HYDROXYL FUNCTIONS
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Versatile use of 4-nitrobenzyl group for protection of hydroxyl functions is described.It can be removed selectively in the presence of other benzyl-type protecting groups such as benzyl and 4-methoxybenzyl via reduction into 4-aminobenzyl group followed by electrochemical oxidation.Very clean oxidative cleavage of 4-aminobenzyl group could also be effected with 2,3-dichloro-5,6-dicyanobenzoquinone after N-acetylation.
- Fukase, Koichi,Tanaka, Hideo,Torii, Sigeru,Kusumoto, Shoichi
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p. 389 - 392
(2007/10/02)
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