Introduction Of Additional Functional Groups Research Articles

Сенсорные свойства углеродных нанотрубок, содержащих примесные атомы бора

Nanotubes, being one of the most sought-after materials in nanotechnology, are finding new applications. One such area is their use as highly sensitive sensors. However, in the practical application of nanotubes, it often turns out that, despite their positive sorption properties, the change in their electronic state does not occur after the capture of the analyzed substance. This fact significantly complicates the possibility of their use as sensor nanosensors. One of the ways to improve the electronic properties of carbon nanotubes by creating heterostructures on their surface is by modifying them with different atoms. In this case, one of the most effective for the substitution reaction is boron. It enables the creation of redistribution of electron density on the surface of nanotubes while making no significant changes to the topology of the nanotube surface. This paper analyzes a model experiment to study the possibility of using the nanotubes themselves as highly sensitive nanosensors with respect to carbon dioxide molecules. It is concluded that in order to control the sorption properties of carbon nanotubes for their use in fire-fighting devices, it is sufficient to modify them with impurity boron atoms without the introduction of additional functional groups.

Regio- and Enantioselective Catalytic δ-C-H Amidation of Dioxazolones Enabled by Open-Shell Copper-Nitrenoid Transfer.

Controlling regio- and enantioselectivity in C-H functionalization reactions is of paramount importance due to their versatile synthetic utilities. Herein, we describe a new approach for the asymmetric δ-C(sp3)-H amidation catalysis of dioxazolones using a Cu(I) precursor with a chiral bisoxazoline ligand to access six-membered lactams with high to excellent regio- and enantioselectivity (up to >19:1 rr and >99:1 er). Combined experimental and computational mechanistic studies unveiled that the open-shell character of the postulated Cu-nitrenoids enables the regioselective hydrogen atom abstraction and subsequent enantio-determining radical rebound of the resulting carbon radical intermediates. The synthetic utility of this asymmetric cyclization was demonstrated in the diastereoselective introduction of additional functional groups into the chiral δ-lactam skeleton as well as in the rapid access to biorelevant azacyclic compounds.

Discovery of N-sulfonylated aminosalicylic acids as dual MCL-1/BCL-xL inhibitors.

The anti-apoptotic protein MCL-1, which is overexpressed in multiple cancers, is presently a focus for the development of targeted drugs in oncology. We previously discovered inhibitors of MCL-1 based on 1-sulfonylated 1,2,3,4-tetrahydroquinoline-6-carboxylic acids ("1,6-THQs"). However, with the nitrogen atom constrained in the bicyclic ring, we were unable to modify the alkyl portion of the tertiary sulfonamide functionality. Moreover, the introduction of additional functional groups onto the benzene ring portion of the THQ bicycle would not be trivial. Therefore, we elected to deconstruct the piperidine-type ring of the 6-carboxy-THQ lead to create a new 4-aminobenzoic acid scaffold. Given its simplicity, this permitted us to introduce diversity at the sulfonamide nitrogen, as well as vary the positions and substituents of the benzene ring. One of our most potent MCL-1 inhibitors, 6e-OH, exhibited a K i of 0.778 μM. Heteronuclear single quantum coherence experiments suggested 6e-OH bound in the canonical BH3-binding groove, with significant perturbations of R263, which forms a salt bridge with MCL-1's pro-apoptotic binding partners, as well as residues in the p2 pocket. Selectivity studies indicated that our compounds are dual inhibitors of MCL-1 and BCL-xL, with 17cd the most potent dual inhibitor: K i = 0.629 μM (MCL-1), 1.67 μM (BCL-xL). Whilst selective inhibitors may be more desirable in certain instances, polypharmacological agents whose additional target(s) address other pathways associated with the disease state, or serve to counter resistance mechanisms to the primary target, may prove particularly effective therapeutics. Since selective MCL-1 inhibition may be thwarted by overexpression of sister anti-apoptotic proteins, including BCL-xL and BCL-2, we believe our work lays a solid foundation towards the development of multi-targeting anti-cancer drugs.

Synthesis and properties of ion-exchange materials based on hydrolysis lignins

Hydrolytic lignin is a large-tonnage waste product of ethyl alcohol production and is a renewable resource. The structure of lignin is characterized by the presence of a large number of hydroxyl groups, which provides the value of lignin as a raw material for synthesis in polymer chemistry. But due to their low chemical stability in dilute alkalis, acids and solvents, lignins are of little use for wide practical use. The introduction of additional functional groups into the lignin maromolecule by oxidative modification with the use of resource-saving technologies makes it possible to obtain new products for the synthesis of composite materials. On the basis of electrochemically modified lignin in polycondensation reactions with phthalic acid, ion-exchange materials have been obtained: weakly acidic cation exchangers with a exchange capacity of 0.1 mol/l NaOH 3.5-3.8 mmol/cm3, capable of sorbing cations in a wide range of pH values, and ampholyte (exchange capacity for sodium cation 6.4-6.6 mmol/cm3, for chlorine anion - 1.1-1.3 mmol/cm3). Ion exchangers synthesized on the basis of chlorine and nitro-containing lignins have been investigated in comparison with generally known industrial ion exchangers; they have high exchange and physic-mechanical characteristics and chemical resistance.

The Preparation of Tetramethyl 1,1′,3,3′-Ruthenocenetetra­carboxylate and Tetramethyl 1,1′,3,3′-Osmocenetetracarboxylate, and a Simplified Synthesis for Tetramethyl 1,1′,3,3′-Ferrocene­tetracarboxylate

Substituted metallocenes with more than two substituents have to be synthesized using doubly substituted cyclopentadiene rings in a reaction with a metal compound or by the introduction of additional functional groups to an already di-substituted metallocene. The direct formation of tetra-substituted metallocenes often suffers due to insufficient reactivity of the reagents or the resulting product mixtures, which are hard to separate. In this work, a protocol, which was successful in a tetra-substitution of ferrocene by a tetra-metalation followed by a reaction with carbon dioxide, is used to perform the tetra-substitution of ruthenocene and osmocene. In addition, a simplified protocol for the tetra-functionalization of ferrocene using commercially available components on a medium scale is described.

Azidobupramine, an Antidepressant-Derived Bifunctional Neurotransmitter Transporter Ligand Allowing Covalent Labeling and Attachment of Fluorophores.

The aim of this study was to design, synthesize and validate a multifunctional antidepressant probe that is modified at two distinct positions. The purpose of these modifications was to allow covalent linkage of the probe to interaction partners, and decoration of probe-target complexes with fluorescent reporter molecules. The strategy for the design of such a probe (i.e., azidobupramine) was guided by the need for the introduction of additional functional groups, conveying the required properties while keeping the additional moieties as small as possible. This should minimize the risk of changing antidepressant-like properties of the new probe azidobupramine. To control for this, we evaluated the binding parameters of azidobupramine to known target sites such as the transporters for serotonin (SERT), norepinephrine (NET), and dopamine (DAT). The binding affinities of azidobupramine to SERT, NET, and DAT were in the range of structurally related and clinically active antidepressants. Furthermore, we successfully visualized azidobupramine-SERT complexes not only in SERT-enriched protein material but also in living cells stably overexpressing SERT. To our knowledge, azidobupramine is the first structural analogue of a tricyclic antidepressant that can be covalently linked to target structures and further attached to reporter molecules while preserving antidepressant-like properties and avoiding radioactive isotopes.

ChemInform Abstract: Trifluoromethylation of Alkenes with Concomitant Introduction of Additional Functional Groups

AbstractReview: [68 refs.

Trifluoromethylation of alkenes with concomitant introduction of additional functional groups.

The trifluoromethyl group is found in many synthetic bioactive compounds, and the difunctionalization of a C=C bond, as a powerful strategy for the construction of compounds with various functional groups, has been intensively investigated. Therefore, the difunctionalizing trifluoromethylation of alkenes has attracted growing interest because of the potential of the products as building blocks for bioactive molecules. In this review, we focus on recent advances in the trifluoromethylation of alkenes with concomitant introduction of additional functional groups.

Carboranylamidinates

AbstractThis Research Report provides an overview on synthesis, structure, and reactivity of the recently discovered carboranylamidinate ligands. Carboranylamidinate anions of the type [(o‐C2B10H10C(NHR)(=NR)]– (R = iPr, cyclohexyl) are readily accessible via addition of o‐lithiocarborane to N,N′‐carbodiimides R–N=C=N–R. They combine the highly versatile characteristics of both amidinates and carboranes in one unique ligand system. Unlike simple amidinate anions, the carboranylamidinates coordinate to metal ions not as typical N,N′‐chelating ligands but adopt an unexpected κ2C, N‐bonding mode. The free imine functionality in carboranylamidinates can be further deprotonated. The resulting dianions were demonstrated to be excellent starting materials for novel boron‐rich heterocycles incorporating e.g. Si, Sn, P, or transition metals such as Ti, Zr, Rh, and Ir. Further modification of the carboranylamidinate cage structure includes the introduction of additional functional groups like –SH or –SeH as well as the selective removal of a boron atom with formation of novel nido‐type dicarbollylamidinate ligands. An initial study already showed that transition metal carboranylamidinates are potentially useful as polymerization catalysts.

Tandem Ugi MCR/Mitsunobu Cyclization as a Short, Protecting‐Group‐Free Route to Benzoxazinones with Four Diversity Points

AbstractA tandem Ugi/Mitsunobu protocol, starting from o‐aminophenols, α‐hydroxy acids, amines and aldehydes gives benzo[b][1,4]oxazin‐3‐ones of general formula 1 in two high‐yielding steps, with the introduction of up to four diversity inputs. The mildness of the methodology allows the stereospecific synthesis of enantiomerically pure products as well as the introduction of additional functional groups. The overall procedure can also be carried out in a one‐pot manner.

Simple analogues of anthralin: unusual specificity of structure and antiproliferative activity.

Fifty-nine simple analogues of the antipsoriatic agent, anthralin, have been prepared by modifying the positions of the 1,8-hydroxyl groups, replacement of the hydroxyl groups, substitution at the oxygen functions, introduction of additional functional groups into various positions of the anthracenone nucleus, or removal of particular structural elements. The compounds were evaluated for their antiproliferative action against human keratinocytes and inhibition of the generation of leukotriene B4 in polymorphonuclear leukocytes, which may be useful to resolve the proliferative and inflammatory aspects of psoriasis, respectively. Even though many anthracenones were more potent inhibitors of leukotriene biosynthesis than anthralin, none of the compounds was substantially more effective as this drug in suppressing keratinocyte cell growth. There is an absolute requirement for two hydroxyl groups peri to a hydrogen bond acceptor such as a keto or an imino group for high potency. In addition to further delineating the nature of the pharmacophore for this class of compounds, also naphthalenedione with a peri hydroxyl group was identified as a pharmacophore with antiproliferative activity against keratinocyte growth.

Chemospecific manipulations of a rigid polysaccharide: syntheses of novel chitosan derivatives with excellent solubility in common organic solvents by regioselective chemical modifications

Efficient procedures for the preparations of soluble chitosan derivatives have been established on the basis of the regioselective chemical modifications. Selective and quantitative N-phthaloylation of chitosan proceeds smoothly by the reaction of chitosan with phthalic anhydride in N,N-dimethylformamide (DMF) at 130 C. The resulting phthaloylchitosan exhibits much improved solubility in common organic solvents such as DMF, NJV-dimethylacetamide, dimethyl sulfoxide, and pyridine. The enhanced solubility of new types of chitosan derivatives under homogeneous reaction conditions. Facile conversions of phthaloylchitosan, a key starting material, into several 6-0-substituted derivatives are carried out by the reactions with bulky substituents such as triphenylmethyl (trityl) and @-tolylsulfony1)oxy (tosyloxy) groups. These reactions also proceed in homogeneous solution under mild conditions, and the degrees of substitution are estimated to be 1.0. Subsequent 3-0-acetylation of the secondary hydroxyl groups of 6-0-substituted materials gives rise to regioselectively modified chitosan derivatives showing much better solubility. Specific N-dephthaloylation or 0-detritylation of 6-0-trityl derivatives affords versatile intermediates, which permit the introduction of additional functional groups regioselectively.