2577-48-2Relevant articles and documents
Electron transfer through the hydrogen-bonded interface of a β-turn- forming depsipeptide
Williamson, David A.,Bowler, Bruce E.
, p. 10902 - 10911 (1998)
Hydrogen-bonding networks are believed to play an important role in electron-transfer pathways in a protein medium. A porphyrin-quinone donor- acceptor compound with a depsipeptide bridge which forms a β-turn has been synthesized to study hydrogen bond-mediated electron transfer. The placement of the donor and acceptor has been chosen to favor electron transfer through the hydrogen bond interface of the β-turn. Use of ester linkages also allows control of the hydrogen-bonding pattern within the β-turn-forming depsipeptide. Infrared spectroscopy in the amide A (NH stretch) and amide I (carbonyl stretch) regions indicates that the β-turn conformation is about 85% populated in dichloromethane and essentially completely disrupted in dimethyl sulfoxide at 296 K. The electron-transfer rate constant, k(et), was evaluated using the singlet excited-state lifetimes of the porphyrin in the presence and absence of an electron acceptor. The lifetimes were obtained using time-correlated single-photon-counting fluorescence spectroscopy. Very fast electron transfer (k(et) = (1.1 ± 0.1) x 109 s-1) was observed in the presence of the β-turn conformation. When the β-turn structure was disrupted using the solvent DMSO, electron transfer was no longer competitive with the intrinsic fluorescence emission. Analysis of the data in terms of Marcus theory and the pathway model for electronic coupling yielded a value for the hydrogen bond coupling decay factor, ε(hb), of 0.8 ± 0.4, which is of the same order of magnitude as the theoretically predicted value of 0.36.
Psychrophilin E, a new cyclotripeptide, from co-fermentation of two marine alga-derived fungi of the genus Aspergillus
Ebada, Sherif S.,Fischer, Thomas,Hamacher, Alexandra,Du, Feng-Yu,Roth, Yoen Ok,Kassack, Matthias U.,Wang, Bin-Gui,Roth, Eckhard H.
, p. 776 - 781 (2014)
Chemical investigation of the mycelial extract of a mixed culture of two marine alga-derived fungal strains of the genus Aspergillus has yielded one new cyclotripeptide, psychrophilin E (1), the recently reported oxepin-containing alkaloids, protuboxepin A (2) and oxepinamide E (3), together with three other polyketide derivatives (4-6). The chemical structure and relative and absolute configurations of psychrophilin E (1) were unambiguously established based on HRMS, 1D, 2D NMR and chiral-phase HPLC analysis of its hydrolysate. All the isolated compounds were assessed for their anti-proliferative activity against four different human cancer cell lines and some of them revealed selective activities. 2014
Diastereoselective hydrogenation of a tricyclic α,β -dehydrodipeptide
Kukula, Pavel,Prins, Roel
, p. 240 - 244 (2003)
An unsaturated diketopiperazine derivative with a tricyclic α, β-dehydrodipeptide structure was isolated as a reaction intermediate in the hydrogenation of pyrazine-2-(methyl-(S)-prolinecarboxamide). The diastereoselective hydrogenation of this dehydrodipeptide was studied using various noble metals (Pd, Pt, Rh, and Ru) supported on charcoal. The hydrogenation over Pd, Rh, and Ru catalysts proceeded with a high diastereoselectivity (71-79%), and the diastereomer with the (S)-configuration on both chiral carbon atoms was formed preferentially. The reaction rates and diastereoselectivities of the hydrogenation over the Pd, Rh, and Ru catalysts were similar, while the platinum catalyst was much less active and selective (48% d.e.). The obtained results were compared with those of the hydrogenation of pyrazine-2-(methyl-(S)-prolinecarboxamide); two different pathways for the hydrogenation of this molecule were suggested. In one path, cyclization already occurs after hydrogenation to the tetrahydropyrazine molecule, and in the other path cyclization occurs after full hydrogenation of the pyrazine molecule.
Synthesis and properties of novel chiral ionic liquids from L-proline
Gao, Hong-Shuai,Hu, Zhi-Guo,Wang, Jian-Ji,Qiu, Zhao-Fa,Fan, Feng-Qiu
, p. 521 - 525 (2008)
A novel class of chiral ionic liquids with chiral cations directly derived from natural l-proline has been synthesized and their physical properties such as melting point, thermal degradation, and specific rotation have been characterized. Further, their potential use in chiral recognition was demonstrated by studying interactions with racemic Mosher's acid salt. CSIRO 2008.
Conformational analysis and intramolecular interactions of l -proline methyl ester and its N -acetylated derivative through spectroscopic and theoretical studies
Braga, Carolyne B.,Ducati, Lucas C.,Tormena, Claudio F.,Rittner, Roberto
, p. 1748 - 1758 (2014)
This work reports a detailed study regarding the conformational preferences of l-proline methyl ester (ProOMe) and its N-acetylated derivative (AcProOMe) to elucidate the effects that rule their behaviors, through nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies combined with theoretical calculations. These compounds do not present a zwitterionic form in solution, simulating properly amino acid residues in biological media, in a way closer than amino acids in the gas phase. Experimental 3JHH coupling constants and infrared data showed excellent agreement with theoretical calculations, indicating no variations in conformer populations on changing solvents. Natural bond orbital (NBO) results showed that hyperconjugative interactions are responsible for the higher stability of the most populated conformer of ProOMe, whereas for AcProOMe both hyperconjugative and steric effects rule its conformational equilibrium.
Diastereomeric atropisomers from a chiral diyne by cobalt(I)-catalyzed cyclotrimerization
Fischer, Fabian,Jungk, Phillip,Weding, Nico,Spannenberg, Anke,Ott, Holger,Hapke, Marko
, p. 5828 - 5838 (2012)
The reaction of new, chiral, proline-based naphthyl diynes with different nitriles through a key [2+2+2] cycloaddition reaction step catalyzed by Co I-olefin complexes under thermal and photochemical conditions gave diastereomeric atropisomers in good yield and nearly 1:1 ratios. Facile chromatographic separation of the naphthyl tetrahydroisoquinolines gave access to both pure and stable diastereomeric atropisomers. The deprotection and direct functionalization of the methyl-or methoxymethyl-protected 2-naphthyl position of the atropisomers were investigated. The configuration of the formed atropisomers was assigned from results of X-ray studies and circular dichroism spectroscopy.
A transition metal-catalyzed enyne metathesis for the preparation of pyrrolizidine alkaloid core: Application towards the total synthesis of stemaphylline
Kumar, Praveen,Rahman, Md. Ataur,Haque, Ashanul,Singh Yadav, Jhillu
supporting information, (2021/03/03)
In this paper, we disclose an efficient route for the synthesis of pyrrolizidine alkaloid core and its application towards the total synthesis of stemaphylline. The key pyrrolizidine core was achieved with Ru-carbene catalyzed ring closing enyne metathesis (RCEM). The effect of different types and amounts of Ru-carbene catalysts, solvents and temperature were systematically studied. The advantage of this method includes the construction of pyrrolizidine alkaloid core in a single operation.
AN ORAL PHARMACEUTICAL COMPOSITION FOR ALPHA- AMYLASE INHIBITION
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Paragraph 0033-0034, (2021/02/12)
The present invention relates to an oral pharmaceutical composition of synthesized amino acid derivative which is inhibitor of alpha-amylase. In particular, the invention refers to the use of the composition for the treatment of diabetes mellitus type II. The said composition is in the form of a liquid, gel, pill, capsule or tablet.
Modular Synthesis of Alkenyl Sulfamates and β-Ketosulfonamides via Sulfur(VI) Fluoride Exchange (SuFEx) Click Chemistry and Photomediated 1,3-Rearrangement
Sousa E Silva, Felipe Cesar,Doktor, Katarzyna,Michaudel, Quentin
supporting information, p. 5271 - 5276 (2021/07/20)
Herein, we report a synthesis of medicinally relevant β-ketosulfonamides via a photomediated 1,3-rearrangement of alkenyl sulfamates. This protocol tolerates a wide array of sensitive functional groups including alkenes, alkynes, and nitrogen-based heterocycles. Additionally, this work provides a general approach toward alkenyl sulfamates via a two-step Sulfur(VI) Fluoride Exchange (SuFEx) sequence capitalizing on SO2F2 as a linchpin to efficiently couple readily available ketones and amines without a large excess of either partner.