- AB2-type amphiphilic block copolymer containing a pH-cleavable hydrazone linkage for targeted antibiotic delivery
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A novel AB2-type amphiphilic block copolymer [OA-C[dbnd]N-NH-(PEG)2] with hydrazone linkage was synthesized and explored for pH-triggered antibiotic delivery. Vancomycin (VCM) loaded micelles of the polymer [OA-C[dbnd]N-NH-(PEG)2-VCM] were spherical in shape with size, polydispersity index, zeta potential and entrapment efficiency of 130.33 ± 7.36 nm, 0.163 ± 0.009, ?4.33 ± 0.55 mV and 39.61 ± 4.01% respectively. The dilution stability study exhibited no significant change in the size distribution of OA-C[dbnd]N-NH-(PEG)2-VCM micelles up to 320-fold dilution. An in vitro drug release assay confirmed greater release of VCM from OA-C[dbnd]N-NH-(PEG)2-VCM at pH 6, compared to pH 7.4. An in vitro antibacterial activity evaluation of OA-C[dbnd]N-NH-(PEG)2-VCM showed 2-fold enhancement in antibacterial activity of VCM after 54 h of incubation against Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) at acidic pH compared to physiological pH. An in vivo antibacterial activity of OA-C[dbnd]N-NH-(PEG)2-VCM further proved the enhanced activity of OA-C[dbnd]N-NH-(PEG)2-VCM against MRSA. In conclusion, micelles from pH-responsive OA-C[dbnd]N-NH-(PEG)2 could be utilized for site-specific delivery of VCM at the infection site.
- Sonawane, Sandeep J.,Kalhapure, Rahul S.,Jadhav, Mahantesh,Rambharose, Sanjeev,Mocktar, Chunderika,Govender, Thirumala
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- Amido Complexes of Iridium with a PNP Pincer Ligand: Reactivity toward Alkynes and Hydroamination Catalysis
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The pincer ligand HN(CH2CH2PPh2)2 (1; PNHP) reacted with [{Ir(μ-X)(cod)}2] (X = Cl, OMe), affording complexes [fac-(PNHP)Ir(cod)]Cl (2) and [fac-(PNP)Ir(cod)] (3), respectively. The X-ray molecular structure of 2 showed that the PNP ligand coordinates in a facial fashion, with the N atom in an axial site and both P atoms coordinated in the equatorial plane. Compound 1 is able to protonate the hydroxo bridges in the complex [{Ir(μ-OH)(coe)2}2] forming the new amido complex [mer-(PNP)Ir(coe)] (4). Complex 4 is an extremely air sensitive compound, as confirmed by the isolation of the oxo complex [mer-(PNP)Ir(σ2-O2)] (8) from its interaction with air. Protonation of 4 with HBF4 afforded the corresponding amino complex [mer-(PNHP)Ir(coe)]BF4 (5), whose molecular structure enlightened by X-ray crystallography confirmed the PNP ligand to be coordinated in a meridional fashion. The coe ligand in 4 is tightly bonded to iridium; however, under an atmosphere of ethylene at 60 °C or with acrylonitrile at 70 °C complex 4 exchanges the olefin, affording compounds [mer-(PNP)Ir(σ2-C2H4)] (6) and [mer-(PNP)Ir(σ2-C2H3CN)] (7), respectively. Interaction of 4 with alkynes depends on the nature of the substrate; therefore, methyl phenylpropiolate reacted with 4, affording the adduct [mer-(PNP)Ir(σ2-PhCCC(O)OMe)] (9), while the parent acetylene undergoes a double C-H activation, affording the Ir(III) complex [fac-(PNHP)IrH(Ca‰?CH)2] (10). A DFT theoretical analysis of this transformation supports a metal-ligand cooperation mechanism. The reaction starts by deprotonation of an alkyne moiety by the PNP ligand followed by oxidative addition of the C-H bond to the metal of a second alkyne molecule. Additionally, we have tested complex 4 as a catalyst for the addition of gaseous ammonia to activated unsaturated substrates. A DFT theoretical analysis disclosed the operative mechanism on these organic transformations, which starts with a nucleophilic attack of ammonia to the bound alkyne, hydrogen migration to the metal, and reductive elimination steps.
- Hermosilla, Pablo,López, Pablo,García-Ordunìa, Pilar,Lahoz, Fernando J.,Polo, Víctor,Casado, Miguel A.
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p. 2618 - 2629
(2018/08/21)
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- RECYCLABLE CATALYSTS FOR CHLORINATION OF ORGANIC ACIDS AND ALCOHOLS
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The present invention discloses recyclable polymeric catalyst of Formula I, for chlorination of organic acids and alcohols using chlorinating agents such as carbonyl chloride, oxalyl chloride or thionyl chloride, wherein, ‘m’ on the pendent groups on polystyrene backbone can have values from 1 to 5 and R is the alkyl group ranging from C1 to C5.
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Paragraph 0080-0082
(2017/10/10)
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- FREE-STANDING NON-FOULING POLYMERS, THEIR COMPOSITIONS, AND RELATED MONOMERS
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Free-standing non-fouling polymers and polymeric compositions, monomers and macromonomers for making the polymers and polymeric compositions, objects made from the polymers and polymeric compositions, and methods for making and using the polymers and polymeric compositions.
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Page/Page column 55; 56; 57
(2017/01/23)
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- Parent-amido (NH2) palladium(II) complexes: Synthesis, reactions, and catalytic hydroamination
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The treatment of [PdL3(NH3)](OTf)n (n = 1; L3 = (PEt3)2(Ph), (2,6-(Cy2PCH2)2C6H3), n = 2; L3 = (dppe)(NH3)) with NaNH2 in tetrahydrofuran at ambient temperature or -78 °C afforded the dimeric and monomeric parent-amido palladium(II) complexes anti-[Pd(PEt3)(Ph)(μ-NH2)]2 (1), [Pd(dppe)(μ-NH2)]2(OTf)2 (2), and Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3), respectively. The molecular structures of the amido-bridged (μ-NH2) dimeric complexes 1 and 2 were determined by single-crystal X-ray crystallography. The monomeric amido complex 3 reacted with trace amounts of water to give a hydroxo complex, Pd(2,6-(Cy2PCH2)2C6H3)(OH) (4). Exposing complex 3 to an excess of water resulted in the complete conversion of the complex into two species [Pd(2,6-(Cy2PCH2)2C6H3)(OH2)]+ and [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]+. Complex 3 reacted with diphenyliodonium triflate ([Ph2I]OTf) to give the aniline complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf. The reaction of 3 with phenylacetylene (HCCPh) yielded a palladium(II) acetylenide Pd(2,6-(Cy2PCH2)2C6H3)(CCPh) (5), quantitatively, along with the liberation of ammonia. The reaction of 3 with dialkyl acetylenedicarboxylate yielded diastereospecific palladium(II) vinyl derivatives (Z)-Pd(2,6-(Cy2PCH2)2C6H3)(CRCR(NH2)) (R = CO2Me (6a), CO2Et (6b)). The reaction of complexes 6a and 6b with p-nitrophenol produced Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) and cis-CHRCR(NH2), exclusively. Reactions of 3 with either dialkyl maleate (cis-(CO2R)CHCH(CO2R)) (R = CH3, CH2CH3) or cis-stilbene (cis-CHPhCHPh) did not result in any addition product. Instead, isomerization of the cis-isomers to the trans-isomers occurred in the presence of catalytic amounts of 3. Complex 3 reacted with a stoichiometric amount of acrylonitrile (CH2CHCN) to generate a metastable insertion product, Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)CH2NH2). On the other hand, the reaction of 3 with an excess of acrylonitrile slowly produced polymeric species of acrylonitrile. The catalytic hydroamination of olefins with NH3 was examined in the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf), producing a range of hydroaminated products of primary, secondary, and tertiary amines with different molar ratios of more than 99% overall yield. A mechanistic feature for the observed catalytic hydroamination is described with regard to the aminated derivatives of palladium(II).
- Kim, Youngwon,Park, Soonheum
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p. 614 - 629
(2016/06/01)
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- Oxidative N-nitration of secondary amines
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Reaction of secondary amines with the nitrite anion assisted by diacetoxyiodobenzene results in respective N-nitroamines. It is the first example of oxidative nitration of the amino group. N-Nitrosoamines are by-products. The yields and the ratio of the nitration and nitrosation products depend on the nature of the starting amine, cation of the salt used, and the solvent.
- Anikin,Pokhvisneva,Lipilin,Mezhenin,Tartakovsky
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experimental part
p. 2043 - 2046
(2011/01/05)
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- MICHAEL-TYPE ADDITION OF DIETHYL PHOSPHORAMIDATE TO α,β-UNSATURATED ESTERS
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Michael-type addition of diethyl phosphoramidate to α,β-unsaturated esters occurs when the reactants are refluxed in toluene or xylene with an excess of potassium carbonate in the presence of tetrabutylammonium bromide (TBABr).Dephosphorylation of methyl and ethyl acrylate adducts leads to the respective β-alanine esters. Key words: Diethyl phosphoramidate; α,β-unsaturated esters; Michael-type addition; β-alanine esters; phase-transfer catalysis.
- Osowska-Pacewicka, K.,Zawadzki, S.,Zwierzak, A.
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