The Experts below are selected from a list of 1002 Experts worldwide ranked by ideXlab platform
Robert Langer - One of the best experts on this subject based on the ideXlab platform.
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degradable poly β amino Esters synthesis characterization and self assembly with plasmid dna
Journal of the American Chemical Society, 2000Co-Authors: Robert LangerAbstract:Poly(β-aminoEsters) 1−3 were synthesized via the addition of N,N‘-dimethylethylenediamine, piperazine, and 4,4‘-trimethylenedipiperidine to 1,4-butanediol diAcrylate. Polymerization proceeded exclusively via the conjugate addition of the secondary amines to the bis(Acrylate Ester). Polymers were isolated in up to 86% yields with molecular weights ranging up to 31 200 relative to polystyrene standards. The polymers degraded hydrolytically in acidic and alkaline media to yield 1,4-butanediol and β-amino acids 4a−6a and the degradation kinetics were investigated at pH 5.1 and 7.4. In general, the polymers degraded more rapidly at pH 7.4 than at pH 5.1. In initial screening assays, both the polymers and their degradation products were determined to be noncytotoxic relative to poly(ethylene imine), a polymer conventionally employed as a synthetic transfection vector. Polymers 1−3 interacted electrostatically with polyanionic plasmid DNA in water and buffer at physiological pH, as determined by agarose gel elec...
Bansi Lal - One of the best experts on this subject based on the ideXlab platform.
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a novel chemo selective epoxidation across Acrylate Ester synthesis of new water soluble forskolin analogues
Synthetic Communications, 2006Co-Authors: Ashok Kumar Gangopadhyay, Bansi LalAbstract:While removing the TBDMS group from OH protection, a novel epoxidation reaction occurred across Acrylate Ester attached to a forskolin fragment. Besides spectroscopic data, the epoxide formation was confirmed by ring opening with a secondary amine. This unique epoxidation reaction, to our knowledge, is not known in the literature. This reaction led us to discover a simple deblocking protocol. The epoxide and the desired Michael substrates were used to introduce imidazole into forskolin.
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A Novel Chemo‐selective Epoxidation across Acrylate Ester: Synthesis of New Water‐Soluble Forskolin Analogues
Synthetic Communications, 2006Co-Authors: Ashok Kumar Gangopadhyay, Bansi LalAbstract:While removing the TBDMS group from OH protection, a novel epoxidation reaction occurred across Acrylate Ester attached to a forskolin fragment. Besides spectroscopic data, the epoxide formation was confirmed by ring opening with a secondary amine. This unique epoxidation reaction, to our knowledge, is not known in the literature. This reaction led us to discover a simple deblocking protocol. The epoxide and the desired Michael substrates were used to introduce imidazole into forskolin.
Arun K. Ghosh - One of the best experts on this subject based on the ideXlab platform.
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An enantioselective synthesis of the C1C9 segment of antitumor macrolide peloruside A
Tetrahedron Letters, 2003Co-Authors: Arun K. Ghosh, Jae-hun KimAbstract:A stereocontrolled synthesis of the C1-C9 segment of the marine natural product peloruside A is described. The key steps involve Sharpless's catalytic asymmetric dihydroxylation reaction, a chelation-controlled reduction of chiral β-alkoxy ketones to elaborate the syn-1,3-diol functionality and a ring-closing olefin metathesis of a homoallylic alcohol-derived Acrylate Ester to form an α,β-unsaturated δ-lactone.
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An enantioselective synthesis of the C2–C16 segment of antitumor macrolide laulimalide
Tetrahedron Letters, 2000Co-Authors: Arun K. Ghosh, Yong WangAbstract:Abstract An enantioselective synthesis of the C 2 –C 16 segment of the novel antitumor agent laulimalide is described. The key steps involve a highly diastereoselective allylation, ring-closing olefin metathesis of a homoallylic alcohol derived Acrylate Ester, a stereoselective anomeric alkylation and an elaboration of an exo -methylene unit by a Julia olefination reaction.
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A stereoselective synthesis of (+)-boronolide
Tetrahedron Letters, 2000Co-Authors: Arun K. Ghosh, Geoffrey BilcerAbstract:Abstract A stereoselective synthesis of (+)-boronolide is described. The key steps involve a stereoselective reduction of an α-hydroxy ketone, allylation of an α-hydroxy aldehyde and a ring-closing olefin metathesis of a homoallylic alcohol derived Acrylate Ester utilizing Grubbs’ catalyst.
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A stereoselective synthesis of (–)-tetrahydrolipstatin
Chemical Communications, 1999Co-Authors: Arun K. Ghosh, Chunfeng LiuAbstract:A stereoselective synthesis of (–)-tetrahydrolipstatin has been accomplished utilizing olefin metathesis of an Acrylate Ester as the key step.
E Wagner - One of the best experts on this subject based on the ideXlab platform.
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Novel degradable oligoethylenimine Acrylate Ester-based pseudodendrimers for in vitro and in vivo gene transfer
Gene Therapy, 2008Co-Authors: V Russ, H Elfberg, C Thoma, J Kloeckner, M Ogris, E WagnerAbstract:A novel class of cationic hyperbranched polymers, containing branched oligoethylenimine (OEI 800 Da) as core, diAcrylate Esters as linkers and oligoamines as surface modification, was synthesized and evaluated regarding their structure–activity relationship as gene carriers. We show that pseudodendritic core characteristics as well as different surface modifications on the core influence DNA-binding ability, cytotoxicity and transfection efficiency. As most promising gene carrier, the pseudodendrimer HD O, that is, the OEI 800 Da core modified with hexane-1,6-diol diAcrylate and surface-modified with OEI 800 Da, was identified. HD O exhibits efficient DNA-condensing ability to nanosized polyplexes (100–200 nm), low cytotoxicity, a degradation half-life of 3 days at 37 °C at physiological pH and in vitro reporter gene-expression levels similar to high molecular weight linear and branched polyethylenimines (PEIs) (LPEI and BPEI). In vivo studies in mice reveal that HD O/DNA polyplexes upon i.v. tail-vein injection have the potential for transfection of tumor tissue at levels comparable to that obtained with LPEI. Importantly, HD O was better tolerated than LPEI, while transgene expression was more tumor-specific and much lower in all other investigated organs, especially in the lung (15 000-fold lower compared with LPEI).
Deborah D.l. Chung - One of the best experts on this subject based on the ideXlab platform.
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Piezoelectric behavior of three-dimensionally printed Acrylate polymer without filler or poling
Journal of Materials Science, 2018Co-Authors: Patatri Chakraborty, Chi Zhou, Deborah D.l. ChungAbstract:We report the piezoelectric behavior of three-dimensionally layer-by-layer printed (bottom-up stereolithography, 21–46-µm layer thickness) polymer without filler or poling, using unmodified ultraviolet-curable resins (Acrylate Ester for Resin 1, and methAcrylated monomers/oligomers for Resin 2) that are not known to be piezoelectric. The smaller is the layer thickness, the greater is the shear stress in printing, the more is the molecular alignment, the higher is the out-of-plane electric permittivity, and the stronger is the out-of-plane direct piezoelectric effect, as shown by the electric field output decreasing reversibly and the capacitance increasing reversibly upon out-of-plane compression (stress ≥ 0.3 kPa). The piezoelectric effect is not merely due to the applied stress increasing the permittivity. The decrease in the electric field output is quite linear up to a stress of ~ 33 kPa. Decrease in the layer thickness from 46 to 26 µm increases the relative permittivity from 5.3 to 6.1 and increases the piezoelectric coupling coefficient d from 0.13 to 0.24 pC/N. Resin 2 gives a higher d than Resin 1 (0.43 vs. 0.24 pC/N), probably due to the higher viscosity and consequent higher shear stress during printing. The fractional change in capacitance due to the applied stress increases with decreasing layer thickness, is greater for Resin 2 than Resin 1, and increases with decreasing applied electric field, which causes a converse piezoelectric effect. The capacitance increases with increasing applied electric field used to measure the capacitance. The fractional change in capacitance due to the applied electric field decreases with increasing stress.