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1.
First Stereoselective Synthesis of the Cytotoxic Polyketide (4R)‐1‐(3,5‐Dihydroxyphenyl)‐4‐hydroxypentan‐2‐one 下载免费PDF全文
Kothakonda Rajendra Prasad Sudina Purushotham Reddy Katragadda Suresh Babu Janaswamy Madhusudana Rao 《Helvetica chimica acta》2015,98(1):143-147
The first stereoselective synthesis of the cytotoxic polyketide (4R)‐1‐(3,5‐dihydroxyphenyl)‐4‐hydroxypentan‐2‐one ( 1 ) was achieved from readily available propylene oxide and 3,5‐dimethoxybenzyl alcohol. The synthesis involves Jacobsen's hydrolytic kinetic resolution (HKR) and Grignard reaction as key steps. 相似文献
2.
Dr. Gangavaram V. M. Sharma Gajulapati Venkateshwarlu Pothula Purushotham Reddy Dr. Ajit C. Kunwar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11428-11438
In α‐peptides, the 8/10 helix is theoretically predicted to be energetically unstable and has not been experimentally observed so far. Based on our earlier studies on ‘helical induction’ and ‘hybrid helices’, we have adopted the ‘end‐capping’ strategy to induce the 8/10 helix in α‐peptides by using short α/β‐peptides. Thus, α‐peptides containing a regular string of α‐amino acids with alternating chirality were end capped by α/β‐peptides with 11/9‐helical motifs at the termini. Extensive NMR spectroscopy studies of these peptides revealed the presence of a hitherto unknown 8/10‐helical pattern; the H‐bonds in the shorter pseudorings were rather weak. The approach of using short helical motifs to induce new mixed helices in α‐peptides could provide avenues for more versatile design strategies. 相似文献
3.
Tryptophan is an essential amino acid, and understanding the conformational preferences of monomer and dimer is a subject of outstanding relevance in biological systems. An exhaustive first principles investigation of tryptophan ( W ) and its ionized counterparts cations (WC) , anions (WA) , and zwitterions (WZ) has been carried out. A comprehensive and systematic study of tryptophan dimer (WD) conformations resulted in about 62 distinct minima on the potential energy surface. The hydrogen bonds and a variety of noncovalent interactions such as OH‐π, NH‐π, CH‐π, CH‐O, and π‐π interactions stabilized different forms of tryptophan and its dimers. Over all in monomeric conformers which have NH‐O, hydrogen bonds showed higher stability than other conformers. A cursory analysis reveal that the most stable dimers stabilized by hydrogen bonding interactions while the less stable dimers showed aromatic side chain interactions. Protein Data Bank analysis of tryptophan dimers reveals that at a larger distance greater than 5 Å, T‐shaped orientations (CH‐π interactions) are more prevalent, while stacked orientations (π‐π interactions) are predominant at a smaller distance. © 2013 Wiley Periodicals, Inc. 相似文献
4.
Divyaraj Puthran Boja Poojary Soukhyarani G. Nayak Nikil Purushotham Manjunath Bhat Hemant Hedge 《中国化学会会志》2020,67(7):1278-1288
2-amino-5-(3-fluoro-4-methoxyphenyl)thiophene-3-carbonitrile derivatives have been synthesized from 1-(3-fluoro-4-methoxyphenyl)ethanone, malononitrile, mild base, and sulfur powder using the Gewald method through a multistep reaction sequence. The structures of newly synthesized compounds were established on the basis of their elemental analyses, IR, 1H NMR, 13C NMR, and mass spectral data, and then synthesized compounds were screened for their in vitro antimicrobial activity. Among them, derivatives 3b (thiphene), 3f (pyrazole), and 3d (halogen) showed good activity and remaining derivatives exhibited moderate activity. 相似文献
5.
Highly Productive Oxidative Biocatalysis in Continuous Flow by Enhancing the Aqueous Equilibrium Solubility of Oxygen 下载免费PDF全文
Dr. Michael R. Chapman Dr. Sebastian C. Cosgrove Prof. Nicholas J. Turner Prof. Nikil Kapur Prof. A. John Blacker 《Angewandte Chemie (International ed. in English)》2018,57(33):10535-10539
We report a simple, mild, and synthetically clean approach to accelerate the rate of enzymatic oxidation reactions by a factor of up to 100 when compared to conventional batch gas/liquid systems. Biocatalytic decomposition of H2O2 is used to produce a soluble source of O2 directly in reaction media, thereby enabling the concentration of aqueous O2 to be increased beyond equilibrium solubility under safe and practical conditions. To best exploit this method, a novel flow reactor was developed to maximize productivity (g product L?1 h?1). This scalable benchtop method provides a distinct advantage over conventional bio‐oxidation in that no pressurized gas or specialist equipment is employed. The method is general across different oxidase enzymes and compatible with a variety of functional groups. These results culminate in record space‐time yields for bio‐oxidation. 相似文献
6.
The structure and stability of various conformations of L-phenylalanine (PheN) and its zwitterions (PheZ), along with their ionized counterparts, cation (PheC) and anion (PheA), generated by adding and removing a proton respectively, have been investigated using first principle calculations in vacuum and in solution. This is followed by an extensive study on various possible dimer (PheD) conformations, which are noncovalently bound units without a peptide bond. This study results in 52, 31, 12, 9, and 11 minimum energy structures on the potential energy surfaces of PheD, PheN, PheC, PheA, and PheZ, respectively. Several important nonbonded interactions such as hydrogen bonds, NH-π, CH-π, OH-π, and π-π interactions, which impart stability to the monomeric and dimeric units, have been analyzed. The capability and strength of the nonbonded interactions drastically changing the conformational orientations of monomeric units has been illustrated. 相似文献
7.
Baggu Chinnababu Sudina Purushotham Reddy Chitturi Bhujanga Rao Karuturi Rajesh Yenamandra Venkateswarlu 《Helvetica chimica acta》2010,93(10):1960-1966
A simple and highly efficient stereoselective total synthesis of dodoneine ( 1 ), a naturally occurring bioactive 5,6‐dihydro‐2H‐pyran‐2‐one, was achieved. The synthesis involved Keck's asymmetric allylation, iodine‐induced electrophilic cyclization, and Grubbs' catalyzed ring‐closing metathesis as key steps. 相似文献
8.
A highly convergent stereoselective total synthesis of stagonolide F is described starting from commercially available 5-hexen 1-ol using asymmetric dihydroxylation, Jacobsen's hydrolytic kinetic resolution (HKR), regioselective epoxide ring opening with vinyl Grignard reaction, esterification, and ring-closing metathesis (RCM) as key steps. 相似文献
9.
Lattice strains in Mg, Zn and Cd powders produced by grinding have been analyzed by X-ray powder diffraction. The lattice
strain (ɛ) and Debye-Waller factor (B) are determined from the half-widths and integrated intensities of the Bragg reflections. In all three cases viz. Mg, Zn and Cd, the Debye-Waller factor is found to increase with the lattice strain. From the correlation between the strain
and effective Debye-Waller factor, the Debye-Waller factors for zero strain have been estimated for Mg, Zn and Cd. The variation
of energy of vacancy formation as a function of lattice strain has been studied. 相似文献
10.
The chelates of various rare earths with acetylacetone, benzoylacetone, dibenzoylmethane, 2-thenoyltrifluoroacetone and dithenoylmethane were prepared and some of their physical properties noted. The ultraviolet absorption spectra in various non-aqueous solvents were measured. Absorption measurements in the visible region showed alterations in absorption intensities and resolution in some of the principal bands, depending on the solvent. The infrared spectra were measured and compared with literature data. 相似文献