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181.
A rapid assembly of the tetracyclic core of marine diterpenoids related to puupehenone and kampanols by Diels? Alder reaction of 2‐ethenyl‐1,3,3‐trimethylcyclohexene with 4H‐chromen‐4‐one (=4H‐1‐benzopyran‐4‐one) dienophiles is described. 相似文献
182.
Abstract
A rapid assembly of the tetracyclic core of marine diterpenoids related to puupehenone and kampanols featuring a Lewis acid catalyzed [4+2] cycloaddition reaction of 1,3,3-trimethyl-2-vinyl-1-cyclohexene and chromone dienophiles is described. 相似文献183.
K. Kamala Bharathi S. VenkateshG. Markandeyulu C.V. Ramana 《Journal of magnetism and magnetic materials》2011,323(1):51-54
Sm28Fe72 and Sm32Fe68 films of 100 nm thickness were grown using DC magnetron sputter deposition and their structure, magnetization, electrical and Hall resistance characteristics were investigated. An increase in electrical resistivity from 4.75×10−6 to 5.62×10−6 Ω m and from 2.26×10−6 to 2.84×10−6 Ω m for Sm28Fe72 and Sm32Fe68 films, respectively, with decrease in temperature from 300 to 40 K is attributed to the strain induced anisotropy that dominates at lower temperatures. The positive extraordinary Hall coefficients (RS) are observed for both films at 300 and 80 K. The existence of hysteresis indicates that Sm28Fe72 and Sm32Fe68 films possess perpendicular anisotropy at 300 K. Hysteresis loop becomes narrow at 80 K for both Sm28Fe72 and Sm32Fe68 films. Magnetization measurements at 300 K exhibiting small coercive field values of 31 and 49 Oe for Sm28Fe72 and Sm32Fe68 films, respectively, confirm the existence of perpendicular anisotropy at 300 K. 相似文献
184.
Pandey SK Jogdand GF Oliveira JC Mata RA Rajamohanan PR Ramana CV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(46):12946-12954
The synthesis of homochiral homo-oligomers of cis- and trans-3-aminotetrahydrofuran-2-carboxylic acids (parent cis- and trans-furanoid-β-amino acids, referred to as "cis-/trans-FAA") has been carried out to understand their secondary structures and their dependence on the ring heteroatom. The oligomers of two diastereomers have been shown to have a distinct left-handed helicity. The cis-FAA homo-oligomers show a 14-helix structure, in contrast to the homo-oligomers of cis-ACPC, which adopt a sheet like structure. The trans-FAA homo-oligomers were found to adopt a 12-helix structure, the same trend found in trans-ACPC homo-oligomers. With the help of ab initio calculations, the structural features of cis-ACPC and cis-FAA hexamers were compared. We believe that the more compact packing of the cis-FAA hexapeptide should be due to a more favorable interaction between the ring and the backbone amide hydrogen. 相似文献
185.
186.
Pranov Ramana Erwin Adams Patrick Augustijns Ann Van Schepdael 《Electrophoresis》2019,40(18-19):2271-2276
Sulfotransferases are categorized as phase II metabolic enzymes. Human sulfotransferase 1A1 (SULT1A1) is involved in the sulfonation of xenobiotics with aid from the cofactor 3'‐phosphoadenosine‐5'‐phosphosulfate that acts as a sulfonate donor. In this study, we have attempted to immobilize SULT1A1 on magnetic microparticles (MMs). Different functionalized MMs were used to immobilize SULT1A1 and their enzyme activity was compared to the control (enzyme in solution). Paracetamol was used as model substrate. Separation of paracetamol and paracetamol sulfate by CE‐UV was optimized and validated. MMs with epoxy based immobilization of SULT1A1 showed better enzyme activity. Hence, they were tested for repeated usage to allow their implementation for the development of a CE immobilized micro enzyme reactor. 相似文献
187.
L. Roopesh Kumar Vishwanatha Thimmalapura Veladi Panduranga Mandipogula Mahesh P. Venkata Ramana 《合成通讯》2020,50(4):506-515
AbstractA simple and efficient method for the synthesis of aryl amides via oxidative copper-catalyzed coupling of commercially available aryl boronic acids and bench stable Nα-protected amino-acid azides is reported. The potential utility of this protocol is demonstrated through a survey of diversely substituted aryl boronic acids and several side-chain functionalized amino-acid azides, leading to the preparation of the desired amidated products in good to excellent yields. This amide synthesis is suitable for the preparation of amides (such as peptide aryl amides and sterically hindered amino acids) that are not or hardly accessible via classical approaches. 相似文献
188.
Sudhakar Mokenapelli Madhu Gutam Ramana Govu Vijay Kumar Pasala Jayaprakash Rao Yerrabelly 《合成通讯》2019,49(10):1241-1251
A new IBX mediated protocol for regio/chemoselective oxidation of andrographolide (1), a labdane diterpenoid isolated from Andrographis paniculata, is developed. After the initial success of this protocol with andrographolide (1) to provide 19-dehydroandrographolide (5) or 3,19-didehydroandrographolide (6) as major products, the procedure was further applied for the oxidation of hydroxyl functionality in andrographolide derivatives, namely 2, 3, 14, and 16. The process was equally suitable on scales of milligram to gram with ease. Deprotection of C-19-OTBDMS in compounds 15 and 18 was achieved using TBDMS-Cl in acetonitrile-water (8:2) system in good yields. 相似文献
189.
190.
The effects of step function change in suction velocity are investigated for a natural convection flow from a vertical porous flat plate of infinite length in the presence of transverse magnetic field for two cases namely (i) when the plate is suddenly raised to a uniform higher temperature, (ii) when the plate suddenly begins to generate a uniform heat flux at its surface. In (i) the coefficient of heat transfer becomes independent of the Hartmann numberM. In either case for a fixed time t except for correct steady state t→ ∞, the effect of the Hartmann number is to decrease both the velocity of the fluid and the skin-friction at the plate. In the correct steady state the velocity field and the skin-fiiction become independent of the Hartmann number. 相似文献