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61.
62.
A total synthesis of the recently reported triquinane natural product dichomitol, isolated from the fermentation broth of Dichomitus squalens, has been accomplished from the commercially available 1,5-cyclooctadiene through a series of unambiguous synthetic steps. A complete mismatch between the spectral characteristics of the synthetic product and that of the natural product warrants a revision of the structure of dichomitol. 相似文献
63.
Subhash P. Chavan Cherukupally Praveen Pallavi Sharma U.R. Kalkote 《Tetrahedron letters》2005,46(3):439-441
A short synthetic route to (−)-and (+)-bulgecinine, the amino acid moiety of the bulgecins was achieved from the readily available nonchiral pool starting material cis-2-butene-1,4-diol in which a Claisen orthoester rearrangement and a Sharpless asymmetric dihydroxylation were used as the key steps. 相似文献
64.
Time-dependent fluctuations in the distance x(t) between two segments along a polymer are one measure of its overall conformational dynamics. The dynamics of x(t), modeled as the coordinate of a particle moving in a one-dimensional potential well in thermal contact with a reservoir, is treated with a generalized Langevin equation whose memory kernel K(t) can be calculated from the time-correlation function of distance fluctuations C(t) identical with x(0)x(t). We compute C(t) for a semiflexible continuum model of the polymer and use it to determine K(t) via the GLE. The calculations demonstrate that C(t) is well approximated by a Mittag-Leffler function and K(t) by a power-law decay on time scales of several decades. Both functions depend on a number of parameters characterizing the polymer, including chain length, degree of stiffness, and the number of intervening residues between the two segments. The calculations are compared with the recent observation of a nonexponential C(t) and a power law K(t) in the conformational dynamics within single molecule proteins [Min et al., Phys. Rev. Lett. 94, 198302 (2005)]. 相似文献
65.
Dr. Pallavi Singh Deep Chowdhury Dr. Arup Mukherjee 《European journal of organic chemistry》2023,26(3):e202201300
A strategy for the vanadium-catalyzed dehydrative C- and S-alkylation by nucleophilic substitution of benzhydrols with arenes and thiols is reported. The alkylation was achieved with the divanadium oxoperoxo complex [K3(V+5)2(O22−)4(O2−)2(μ-OH)] in water under air. The newly developed transformation could accommodate a broad substrate scope, including (hetero)arenes and thiols (34 examples). Both the symmetrical and unsymmetrical benzhydrols furnished excellent yields of the alkylated product under mild reaction conditions. The scope of this strategy was further extended to synthesize bis-benzylated arenes (poly-arylated products) in high yields and regioselectivities. The green metrics determination of all the alkylated products suggests the technical and environmental benefits of the present protocol. The longevity experiment reveals the catalytic activity was maintained over seven cycles. To understand the mechanism of the present reaction, spectroscopic and kinetic studies were undertaken. This simple protocol, which affords the desired products with water as the by-product, can be achieved under mild conditions without needing a base or other additives. 相似文献
66.
The design and synthesis of novel chiral PNA monomer based on trans-5-aminopipecolic acid is reported. The trans diequatorial disposition of the 1,4 ring substituents in six-membered 5-aminopipecolic acid derivative could be favorable over trans 1,3 axial-equatorial disposition in 4-aminopipecolic acid of PNA. Studies on the synthesis of trans-4/5-aminopipecolyl PNA-eagPNA chimeras and their binding preferences to DNA/RNA in duplex/triplex modes are described. 相似文献
67.
Nine odorant Schiff bases, namely 2-(4-methoxybenzylideneamino) benzoic acid, 2-(benzylideneamino) benzoic acid, 2-(3-phenylallylidene amino) benzoic acid, 2-(3,7-dimethyloct-2,6-enylideneamino) benzoic acid, 2-(3,7-dimethyloct-6-enylideneamino) benzoic acid, 2-(4-isopropylbenzylideneamino)benzoic acid, 2-(3,4-dimethoxybenzylideneamino) benzoic acid, 2-(1-phenylethylideneamino) benzoic acid, and 2-[(4-(2,6,6-trimethylcyclohex-2-enyl)-but-2-enylideneamino)benzoic acid, were prepared by condensation of anthranilic acid with corresponding naturally occurring carbonyl compounds (anisaldehyde, benzaldehyde, cinnamaldehyde, citral, citronellal, cuminaldehyde, veratraldehyde, acetophenone, and α-ionone) employing conventional and microwave irradiation methods. These compounds were characterized with the aid of elemental and spectral (FT-IR, 1H NMR, and 13C NMR) analysis. Microwave irradiation method was efficient in terms of reduced reaction time, solvent use, and increased yields of these compounds without affecting their olfactory characteristics. These Schiff bases also exhibited olfactory characteristics for various fragrance compositions and varied antimicrobial activity against Aspergillus niger, Penicillium chrysogenum, Staphylococcus aureus, and Escherichia coli. 相似文献
68.
Poly(3‐hexyl thiophene)‐b‐poly(N‐isopropyl acrylamide): Synthesis and its composition dependent structural,solubility, thermoresponsive,electrochemical, and electronic properties
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Pallavi Kumari Koomkoom Khawas Sunit Hazra Biplab Kumar Kuila 《Journal of polymer science. Part A, Polymer chemistry》2016,54(12):1785-1794
Conjugated block copolymers consisting of poly(3‐hexyl thiophene) (P3HT) and a thermoresponsive polymer poly(N‐isopropyl acrylamide) (PNIPAM) with varying composition have been synthesized by facile click reaction between alkyne terminated P3HT and azide terminated PNIPAM. The composition‐dependent solubility, thermoresponsive property in water, phase behavior, electrochemical, optical, and electronic properties of the block copolymers were systematically investigated. The block copolymers with higher volume fraction of PNIPAM form thermoresponsive spherical micelles with P3HT‐rich crystalline cores and PNIPAM coronas. Both X‐ray and atomic force microscopic studies indicated that the blocks copolymers showed well‐defined microphase separated nanostructures and the structure depended on the composition of the blocks. The electrochemical study of the block copolymers clearly demonstrated that the extent of charge transport through the block copolymer thin film was similar to P3HT homopolymer without any significant change in the band gap. The block copolymers showed improved or similar charge carrier mobility compared with the pure P3HT depending on the composition of the block copolymer. These P3HT‐b‐PNIPAM copolymers were interesting for fabrication of optoelectronic devices capable of thermal and moisture sensing as well as for studying the thermoresponsive colloidal structures of semiconductor amphiphilic systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1785–1794 相似文献
69.
Krishna Rao Vankalapati Pallavi Alegete Sathyanarayana Boodida 《Biomedical chromatography : BMC》2022,36(7):e5384
A simple, precise, and rapid stability-indicating reversed-phase-HPLC method was developed and validated for the estimation of metformin (MET), dapagliflozin (DAP), and saxagliptin (SAX) combination in bulk and tablet dosage forms. The proposed method uses a Kromasil C18 column (150 × 4.6 mm, 5 μm) with column oven temperature of 30°C and mobile phase containing a mixture of 60% phosphate buffer (pH = 3) and 40% acetonitrile. The flow rate was set at 1.0 mL/min, and the injection volume was 10 μL. The detection was carried out at 230 nm using a photodiode array detector, and the total run time was 4 min. The proposed method was validated according to International Council for Harmonisation (ICH) guidelines for specificity, linearity, precision, accuracy, robustness, and solution stability. The method is linear over the range of 125–750 μg/mL for MET, 1.25–7.5 μg/mL for DAP, and 0.625–3.75 μg/mL for SAX. The observed correlation coefficients (R2) for MET, DAP, and SAX are >0.999. The proposed method is precise, and the percentage relative standard deviation was found to be between 0.4 and 0.8. The observed percentage recoveries were between 98.51 and 100.80 for all three compounds. The product was subjected to stress conditions of acid, base, oxidative, thermal, and photolytic degradation. The product was found to degrade significantly in oxidative, acid, and base hydrolysis degradation conditions, and the degradation products were well determined from the active peaks, thus proving the stability-indicating power of the method. The developed and validated stability-indicating reversed-phase-HPLC method was appropriate for quantitative determination of these drugs in pharmaceutical preparations and also for quality control in bulk manufacturing. 相似文献
70.
Abhimanyu Pallavi Sudhir 《Advances in Applied Clifford Algebras》2014,24(3):805-807
A generalisation of the determinant to rectangular matrices, known as the determinant-like function, has its magnitude defined previously. In this paper, we show that the determinant-like function is a rotation of the vector determinant.We further propose that this rotation is an identity transformation and thus the determinant-like function is in fact the same as the vector determinant. From this, we derive some properties of the determinant-like function. 相似文献