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11.
Synthesis of small cyclic peptides via reverse turn induced ring closing metathesis of tripeptides 总被引:1,自引:0,他引:1
A reverse turn induced (gamma/beta-turn) cyclization of tripeptides 1 can be performed in a ring closing metathesis reaction with Grubbs' catalyst to the corresponding cyclic peptides 2. These cyclic peptides may be useful probes as a conformationally constrained mimic of the bioactive conformation of structurally related HIV protease inhibitors. 相似文献
12.
Force-constant softening due to impurities in Si and Ge has been estimated, using the band model of sievers and Takeno, to be between 10–15%. The molecular model yields a value of about 20% for the same effect. 相似文献
13.
An efficient improved procedure for the synthesis of beta-acetamido carbonyl compounds is developed by a cobalt(II) chloride-catalyzed three-component coupling protocol. The procedure is also amenable to the synthesis of gamma-lactams by a three-component coupling reaction with use of 2-carbomethoxybenzaldehyde. The beta-acetamido carbonyl compounds derived from 2-carbomethoxybenzaldehyde are useful intermediates as they can be transformed to the corresponding gamma-lactams on treatment with base. 相似文献
14.
Ehrke H Tobey RI Wall S Cavill SA Först M Khanna V Garl T Stojanovic N Prabhakaran D Boothroyd AT Gensch M Mirone A Reutler P Revcolevschi A Dhesi SS Cavalleri A 《Physical review letters》2011,106(21):217401
We used ultrafast resonant soft x-ray diffraction to probe the picosecond dynamics of spin and orbital order in La(0.5)Sr(1.5)MnO(4) after photoexcitation with a femtosecond pulse of 1.5 eV radiation. Complete melting of antiferromagnetic spin order is evidenced by the disappearance of a (1/4,1/4,1/2) diffraction peak. On the other hand, the (1/4,1/4,0) diffraction peak, reflecting orbital order, is only partially reduced. We interpret the results as evidence of destabilization in the short-range exchange pattern with no significant relaxation of the long-range Jahn-Teller distortions. Cluster calculations are used to analyze different possible magnetically ordered states in the long-lived metastable phase. Nonthermal coupling between light and magnetism emerges as a primary aspect of photoinduced phase transitions in manganites. 相似文献
15.
Amrutha Prabodh Yichuan Wang Stephan Sinn Paolo Albertini Christian Spies Eduard Spuling Liu-Pan Yang Wei Jiang Stefan Brse Frank Biedermann 《Chemical science》2021,12(27):9420
Fluorescence-detected circular dichroism (FDCD) spectroscopy is applied for the first time to supramolecular host–guest and host–protein systems and compared to the more known electronic circular dichroism (ECD). We find that FDCD can be an excellent choice for common supramolecular applications, e.g. for the detection and chirality sensing of chiral organic analytes, as well as for reaction monitoring. Our comprehensive investigations demonstrate that FDCD can be conducted in favorable circumstances at much lower concentrations than ECD measurements, even in chromophoric and auto-emissive biofluids such as blood serum, overcoming the sensitivity limitation of absorbance-based chiroptical spectroscopy. Besides, the combined use of FDCD and ECD can provide additional valuable information about the system, e.g. the chemical identity of an analyte or hidden aggregation phenomena. We believe that simultaneous FDCD- and ECD-based chiroptical characterization of emissive supramolecular systems will be of general benefit for characterizing fluorescent, chiral supramolecular systems due to the higher information content obtained by their combined use.Fluorescence-detected circular dichroism (FDCD) spectroscopy is applied for the first time to supramolecular host–guest and host–protein systems and compared to the more known electronic circular dichroism (ECD). 相似文献
16.
Photomechanical techniques are developed for studying wave propagation in anisotropic media such as fiber-reinforced composites and rocks. Moiré fringes in transparent and opaque materials, and isochromatic fringes in transparent composites, are photographed at rates up to over one-million frames/second. A Beckman and Whitley 189 framing camera is utilized with illumination provided by argon flashbombs or a special electronic flash. 相似文献
17.
K. Neelakandan H. Manikandan N. Santosha B. Prabhakaran 《Journal of heterocyclic chemistry》2014,51(Z1):E332-E334
The present invention provides a convenient and industrially viable process for preparation of zolmitriptan. The invention specifically relates to a method for obtaining (S)‐4‐(4‐hydrazinobenzyl)‐1,3‐oxazolidin‐2‐one hydrochloride of desired purity by separation and isolation in a particular pH range to give higher yield and purity. 相似文献
18.
Conformationally rigid aromatic amino acids as potential building blocks for abiotic foldamers 总被引:1,自引:0,他引:1
Ramesh VV Roy A Vijayadas KN Kendhale AM Prabhakaran P Gonnade R Puranik VG Sanjayan GJ 《Organic & biomolecular chemistry》2011,9(2):367-369
This communication describes the development of conformationally constrained unnatural aromatic amino acids, constructed on rigid backbone wherein the carboxyl and amino groups project in two dimensions (planes) on the aromatic framework. Such a feature offers the possibility of design and development of conformationally ordered synthetic oligomers with intriguing structural architectures distinct from those classically observed. Furthermore, such amino acids will have the potential to extend the conformational space available for foldamer design with diverse backbone conformation and structural architectures. 相似文献
19.
5,6-Dihydro-4H-1,3-oxazine hydrobromides have been synthesized by the nucleophilic autocyclo-O-alkylation of N-(3-bromopropyl)amides under neutral conditions in chloroform. It is found that electron-donating amide α-substituents influence the autocyclization efficiency. 相似文献
20.