- Zirconium-catalyzed chemoselective methylalumination of ethers, amines, and sulfides bearing two terminal alkenyl groups
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Chemoselectivity in the methylalumination reaction of unsymmetrical ethers, amines, and sulfides bearing two different terminal alkenyl groups, a 13-tetradecenyl group and an allyl, 4-pentenyl or 6-heptenyl group was examined. The methylalumination of the allyl derivatives proceeded with complete chemoselectivity to afford only the 13-tetradecenyl-monomethylated products. In the methylalumination reactions of the 4-pentenyl and the 6-heptenyl derivatives, in addition to the 13-tetradecenyl-monomethylated products, and dimethylated products were also obtained. However, as in the case of the allyl derivatives, monomethylation to the shorter 4-pentenyl or 6-heptenyl group was not observed, except in the case of 6-heptenyl 13-tetradecenyl amine. The unique selectivity was rationalized upon how readily the intramolecular ligand exchange reaction between intermediate zirconocenium-alkene and zirconocenium-heteroatom complexes could occur.
- Takagi, Ryukichi,Igata, Nao,Yamamoto, Kazuhiro,Kojima, Satoshi
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- Application of intramolecular D?tz reaction to the synthesis of ansa-compounds: concise synthesis of arnebinol
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Fischer carbene complexes having long alkynyloxy chains regioselectively produced oxametacyclophanes via the intramolecular D?tz reaction. The utility of this reaction was demonstrated in the synthesis of arnebinol, an ansa-type terpenoid, from geranyl acetate in six steps.
- Watanabe, Masahito,Tanaka, Kyosuke,Saikawa, Yoko,Nakata, Masaya
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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 181; 182
(2021/02/26)
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- ω-Functionalized Lipid Prodrugs of HIV NtRTI Tenofovir with Enhanced Pharmacokinetic Properties
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Tenofovir (TFV) is the cornerstone nucleotide reverse transcriptase inhibitor (NtRTI) in many combination antiretroviral therapies prescribed to patients living with HIV/AIDS. Due to poor cell permeability and oral bioavailability, TFV is administered as one of two FDA-approved prodrugs, both of which metabolize prematurely in the liver and/or plasma. This premature prodrug processing depletes significant fractions of each oral dose and causes toxicity in kidney, bone, and liver with chronic administration. Although TFV exalidex (TXL), a phospholipid-derived prodrug of TFV, was designed to address this issue, clinical pharmacokinetic studies indicated substantial hepatic extraction, redirecting clinical development of TXL toward HBV. To circumvent this metabolic liability, we synthesized and evaluated ω-functionalized TXL analogues with dramatically improved hepatic stability. This effort led to the identification of compounds 21 and 23, which exhibited substantially longer t1/2 values than TXL in human liver microsomes, potent anti-HIV activity in vitro, and enhanced pharmacokinetic properties in vivo.
- Bartsch, Perry W.,Basson, Adriaan E.,Burton, Samantha L.,Bushnev, Anatoliy,D'Erasmo, Michael,Dasari, Madhuri,Derdeyn, Cynthia A.,Giesler, Kyle E.,Hwang, Soyon S.,Iskandar, Sabrina,Liotta, Dennis C.,Miller, Eric J.,Pribut, Nicole,Raghuram, Akshay,Sharma, Savita K.
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p. 12917 - 12937
(2021/09/13)
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- Membrane properties of amacrocyclic tetraether bisphosphatidylcholine lipid: Effect of a single membrane-spanning polymethylene cross-linkage between two head groups of ditetradecylphosphatidylcholine membrane
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The plasma membranes of archaea are abundant in macrocyclic tetraether lipids that contain a single or double long transmembrane hydrocarbon chains connecting the two glycerol backbones at both ends. In this study, a novel amacrocyclic bisphosphatidylcholine lipid bearing a single membrane-spanning octacosamethylene chain, 1,1’-O-octacosamethylene-2,2′-di-O-tetradecyl-bis-(sn-glycero)-3,3′-diphosphocholine (AC-(di-O-C14PC)2), was synthesized to elucidate effects of the interlayer cross-linkage on membrane properties based on comparison with its corresponding diether phosphatidylcholine, 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (DTPC), that forms bilayer membrane. Several physicochemical techniques demonstrated that while AC-(di-O-C14PC)2 monolayer, which adopts a particularly high-ordered structure in the gel phase, shows remarkably high thermotropic transition temperature compared to DTPC bilayer, the fluidity of both phospholipids above the transition temperature is comparable. Nonetheless, the fluorescent dye leakage from inside the AC-(di-O-C14PC)2 vesicles in the fluid phase is highly suppressed. The origin of the membrane properties characteristic of AC-(di-O-C14PC)2 monolayer is discussed in terms of the single long transmembrane hydrophobic linkage and the diffusional motion of the lipid molecules.
- Tsuchida, Naoyuki,Takagi, Toshiyuki,Takahashi, Hiroshi,Yoshihara, Toshitada,Tobita, Seiji,Sonoyama, Masashi
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- A Sequential Homologation of Alkynes and Aldehydes for Chain Elongation with Optional 13C-Labeling
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Terminal alkynes (RCCH) are homologated by a sequence of ruthenium-catalyzed anti-Markovnikov hydration of alkyne to aldehyde (RCH2CHO), followed by Bestmann-Ohira alkynylation of aldehyde to chain-elongated alkyne (RCH2CCH). Inverting the sequence by starting from aldehyde brings about the reciprocal homologation of aldehydes instead. The use of 13C-labeled Bestmann-Ohira reagent (dimethyl ((1-13C)-1-diazo-2-oxopropyl)phosphonate) for alkynylation provides straightforward access to singly or, through additional homologation, multiply 13C-labeled alkynes. The labeled alkynes serve as synthetic platform for accessing a multitude of specifically 13C-labeled products. Terminal alkynes with one or two 13C-labels in the alkyne unit have been submitted to alkyne-azide click reactions; the copper-catalyzed version (CuAAC) was found to display a regioselectivity of >50 000:1 for the 1,4- over the 1,5-triazine isomer, as shown analytically by 13C NMR spectroscopy.
- Brunner, Andreas,Hintermann, Lukas
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p. 2787 - 2792
(2016/02/27)
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- Tetris in monolayers: Patterned self-assembly using side chain shape
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The "kinked" shapes of conjugated alkadiynes constrain chain packing in monolayers on HOPG. Centrally located diyne units permit assembly of 1,5-bis(alkadiyne)anthracene monolayers. Off-center diynes inhibit self-assembly. Shape matched pairs of off-center diyne chains direct self-assembly of compositionally patterned, two component monolayers.
- Xue, Yi,Zimmt, Matthew B.
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supporting information; experimental part
p. 8832 - 8834
(2011/09/16)
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- Catalytic asymmetric synthesis of macrocyclic (E)-allylic alcohols from ω-alkynals via intramolecular 1-alkenylzinc/aldehyde additions
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The ω-alkynals yielded macrocyclic (S)-allylic alcohols in a one-pot reaction sequence involving alkyne monohydroboration, boron to zinc transmetalation, and ((+)-DAIB)-catalyzed enantioselective intramolecular ring closure to the aldehyde function. A general study of this macrocyclization methodology is presented with respect to ligand type, size, and nature of the formed rings.
- Oppolzer,Radinov,El-Sayed
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p. 4766 - 4770
(2007/10/03)
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- Synthesis and thermotropic properties of macrocyclic lipids related to archaebacterial membranes
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Macrocyclic phospholipids containing 32-44 ring atoms were synthesized by a route involving a high-temperature Glaser oxidation as the key step. These lipids are analogous to mammalian phospholipids except a single extra carboncarbon bond joins the chain termini. The new lipids offered, therefore, an opportunity to examine thermotropic properties of their membranes when the chains within a given molecule are unable to move independently of one another. It was concluded that chain "tethering" (a) raises the transition temperatures substantially for all but the shortest lipids, (b) lowers enthalpies of transition by, in part, reducing the number of gauche C-C linkages created during the melting process, and (c) lowers entropies of transition by impeding motional freedom within the liquid-crystalline phase. Molecular mechanics calculations on the macrocyclic lipids are described briefly.
- Menger,Chen,Brocchini,Hopkins,Hamilton
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p. 6600 - 6608
(2007/10/02)
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