38279-34-4Relevant academic research and scientific papers
Bidirectional metal-free ROMP from difunctional organic initiators
Lu, Pengtao,Alrashdi, Nasser M.,Boydston, Andrew J.
, p. 2977 - 2982 (2017)
Ring-opening metathesis polymerization (ROMP) has enabled access to a diverse array of polymeric materials. Inspired by the breadth of tunability afforded by metal-mediated ROMP, opportunities from an organocatalyzed variant were investigated. We first investigated divinyl ether initiators with different relative orientation of alkoxy moieties. Our intention was to preserve the spacing between reactive sites of the vinyl ethers while varying the nature of the monomer incorporation. Specifically, initiator 1 would incorporate monomers via insertion at the center of the outwardlygrowing polymer, whereas initiator 2 would propagate via an active chain end mechanism. Each initiator was found to undergo metal-free ROMP of norbornene (3) under previously reported conditions using 2,4,6-tris(4-methoxyphenyl)pyrylium tetrafluoroborate (4) as a photoredox catalyst. In comparison with 1, initiator 2 also proceeded with high conversion of monomer although the initiator efficiency was found to be lower than for 1, and more consistent with previous polymerizations using ethyl propenyl ether. Attempts to identify products of deleterious reaction pathways from the initiators were met with limited success. Despite the differences in initiator efficiency, we found that 1 and 2 gave comparable rates of polymerization.
Selective Macrocycle Formation in Cavitands
Yang, Ji-Min,Yu, Yang,Rebek, Julius
, p. 2190 - 2193 (2021)
The traditional end-to-end cyclization of long-chain linear precursors is difficult and often unpredictable because the unfavorable entropy of macrocyclic closure allows undesired intermolecular reactions to compete. Here, we apply cavitands to the selective intramolecular aldol/dehydration reaction of long-chain α,ω-dialdehydes in aqueous solution. Hydrophobic forces drive the dialdehydes into the cavitands in folded conformations and favor macrocyclization reactions over intermolecular reactions observed in bulk solution. The macrocyclic aldol reaction products are isolated in good yields (30-85%) over a wide range (11 to 17-membered rings). Unlike conventional templates that become guests inside their assembled hosts, cavitands reverse the roles and resemble the situation in biological catalysis - the templates are hosts for guests undergoing the assisted reaction processes.
Bis-desulfoglucosinolates: A new class of bolaforms
Lafont, Dominique,Chevalier, Yves,Grumel, Valerie,Cassel, Stephanie,Rollin, Patrick
, p. 2919 - 2930 (2002)
Bis-desulfoglucosinolates 14-18 bearing D-gluco, lacto, malto and cellobio saccharidic moieties were synthesized in two steps from the corresponding protected 1-thio-β-D-glycopyranoses 5, 8, 10 and 12 and bis-hydroximoyl chlorides 3a and 4a derived from 1,8-octanedial (1) and 1,12-dodecanedial (2). Fully deprotections of the intermediate O-acetylated derivatives 6, 7, 9, 11 and 13 were realized either using Zemplen method or methanol/triethylamine/water mixture, the choice of the conditions being dependent on the solubility in methanol of the fully and partially acetylated derivatives.
An Engineered Alcohol Oxidase for the Oxidation of Primary Alcohols
Heath, Rachel S.,Birmingham, William R.,Thompson, Matthew P.,Taglieber, Andreas,Daviet, Laurent,Turner, Nicholas J.
, p. 276 - 281 (2019/01/04)
Structure-guided directed evolution of choline oxidase has been carried out by using the oxidation of hexan-1-ol to hexanal as the target reaction. A six-amino-acid variant was identified with a 20-fold increased kcat compared to that of the wild-type enzyme. This variant enabled the oxidation of 10 mm hexanol to hexanal in less than 24 h with 100 % conversion. Furthermore, this variant showed a marked increase in thermostability with a corresponding increase in Tm of 20 °C. Improved solvent tolerance was demonstrated with organic solvents including ethyl acetate, heptane and cyclohexane, thereby enabling improved conversions to the aldehyde by up to 30 % above conversion for the solvent-free system. Despite the evolution of choline oxidase towards hexan-1-ol, this new variant also showed increased specific activities (by up to 100-fold) for around 50 primary aliphatic, unsaturated, branched, cyclic, benzylic and halogenated alcohols.
Synthesis of bis-4H-furo[3,4-b]indoles
McGowan, Meredeth A.,Perreault, Denise M.,Thornton, Nancy B.,Garaas, Sarah D.,Gribble, Gordon W.
, p. 334 - 347 (2018/09/10)
We describe the synthesis of two novel bis-4H-furo[3,4-b]indoles from indole. Several alternative pathways to these potential DNA bis-intercalator precursors are discussed, and the synthesis of a novel semi-rigid tether is reported.
BIPOLAR TETRAETHER LIPIDS
-
Paragraph 0385; 0390; 0391, (2017/03/21)
Disclosed herein, inter alia, are compounds, compositions, and liposomes and methods of thereof.
A Two-Component Alkyne Metathesis Catalyst System with an Improved Substrate Scope and Functional Group Tolerance: Development and Applications to Natural Product Synthesis
Schaubach, Sebastian,Gebauer, Konrad,Ungeheuer, Felix,Hoffmeister, Laura,Ilg, Marina K.,Wirtz, Conny,Fürstner, Alois
supporting information, p. 8494 - 8507 (2016/07/11)
Although molybdenum alkylidyne complexes such as 1 endowed with triarylsilanolate ligands are excellent catalysts for alkyne metathesis, they can encounter limitations when (multiple) protic sites are present in a given substrate and/or when forcing conditions are necessary. In such cases, a catalyst formed in situ upon mixing of the trisamidomolybenum alkylidyne complex 3 and the readily available trisilanol derivatives 8 or 11 shows significantly better performance. This two-component system worked well for a series of model compounds comprising primary, secondary or phenolic -OH groups, as well as for a set of challenging (bis)propargylic substrates. Its remarkable efficiency is also evident from applications to the total syntheses of manshurolide, a highly strained sesquiterpene lactone with kinase inhibitory activity, and the structurally demanding immunosuppressive cyclodiyne ivorenolide A; in either case, the standard catalyst 1 largely failed to effect the critical macrocyclization, whereas the two-component system was fully operative. A study directed toward the quinolizidine alkaloid lythrancepine I features yet another instructive example, in that a triyne substrate was metathesized with the help of 3/11 such that two of the triple bonds participated in ring closure, while the third one passed uncompromised. As a spin-off of this project, a much improved ruthenium catalyst for the redox isomerization of propargyl alcohols to the corresponding enones was developed.
Cyclohexane Rings Reduce Membrane Permeability to Small Ions in Archaea-Inspired Tetraether Lipids
Koyanagi, Takaoki,Leriche, Geoffray,Onofrei, David,Holland, Gregory P.,Mayer, Michael,Yang, Jerry
supporting information, p. 1890 - 1893 (2016/02/03)
Extremophile archaeal organisms overcome problems of membrane permeability by producing lipids with structural elements that putatively improve membrane integrity compared to lipids from other life forms. Herein, we describe a series of lipids that mimic some key structural features of archaeal lipids, such as: 1) single tethering of lipid tails to create fully transmembrane tetraether lipids and 2) the incorporation of small rings into these tethered segments. We found that membranes formed from pure tetraether lipids leaked small ions at a rate that was about two orders of magnitude slower than common bilayer-forming lipids. Incorporation of cyclopentane rings into the tetraether lipids did not affect membrane leakage, whereas a cyclohexane ring reduced leakage by an additional 40 %. These results show that mimicking certain structural features of natural archaeal lipids results in improved membrane integrity, which may help overcome limitations of many current lipid-based technologies.
Effect of Headgroups on Small-Ion Permeability across Archaea-Inspired Tetraether Lipid Membranes
Koyanagi, Takaoki,Leriche, Geoffray,Yep, Alvin,Onofrei, David,Holland, Gregory P.,Mayer, Michael,Yang, Jerry
, p. 8074 - 8077 (2016/06/14)
This paper examines the effects of four different polar headgroups on small-ion membrane permeability from liposomes comprised of Archaea-inspired glycerolmonoalkyl glycerol tetraether (GMGT) lipids. We found that the membrane-leakage rate across GMGT lipid membranes varied by a factor of ≤1.6 as a function of headgroup structure. However, the leakage rates of small ions across membranes comprised of commercial bilayer-forming 1-palmitoyl-2-oleoyl-sn-glycerol (PO) lipids varied by as much as 32-fold within the same series of headgroups. These results demonstrate that membrane leakage from GMGT lipids is less influenced by headgroup structure, making it possible to tailor the structure of the polar headgroups on GMGT lipids while retaining predictable leakage properties of membranes comprised of these tethered lipids. Extremophiles require robust membranes with low ion permeability to survive in harsh conditions. These Archaea organisms achieve low membrane permeability, in part, by generating lipids with unusual structural features such as tethering of their lipid tails. A systematic study probing the effect of polar headgroups in synthetic Archaea-inspired lipids showed little dependence of membrane leakage rates of small ions as a function of headgroup structure.
Aerobic epoxidation catalysed by transition metal substituted polyfluorooxometalates
Bugnola, Marco,Neumann, Ronny
, p. 14534 - 14537 (2016/09/28)
First row transition metal substituted polyfluorooxmetalates with quasi Wells-Dawson structures and a nitro terminal ligand, [NaH2M(NO2)W17F6O55]q-, were used as catalysts for the aerobic epoxidation of cyclic alkenes. The Cu(NO2) analog combined the best traits of conversion and selectivity. Some C-C bond cleavage was also observed and cis isomers reacted preferentially without stereochemical inversion indicating an oxygen atom to double bond concerted reaction.
