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.
Comparison of enantioselective reductions using bead and monolith 'disk' polymer formulations of CBS catalysts
Varela, Michael C.,Dixon, Seth M.,Price, Michael D.,Merit, Jeffrey E.,Berget, Patrick E.,Shiraki, Saori,Kurth, Mark J.,Schore, Neil E.
, p. 3334 - 3339 (2007)
Two polymer-supported versions of the Corey, Bakshi, and Shibata (CBS) catalyst were prepared and examined. Polymeric beads, with the auxiliary bound in pendant and crosslinked fashion, were prepared utilizing an improved procedure based upon earlier work. Optimization of a procedure for ketone reduction gives results that match those in solution. Attempted reuse gave mixed results. For comparison purposes, CBS functionalized monoliths were formed and tested but performed poorly.
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
Synthesis of pyrrolo- and pyrido[1,2-a]xanthene [1,9-de]azepines: A study of the azepine ring construction
De La Fuente, M. Carmen,Dominguez, Domingo
, p. 8804 - 8810 (2007)
(Chemical Equation Presented) Pentacyclic pyrrolo- and pyrido[1,2-a] xanthene[1,9-de]azepines were synthesized in various oxidation states by assembling the azepine ring following two strategies: 7-endo-trig cyclization of the aryl radical derived from a γ-methylene lactam and cyclodehydration of aldehydes. Other strategies examined (Heck reaction and intramolecular acylation) did not afford azepines, but six-membered nitrogenated rings.
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 of new mono- and bisorganophosphorus proline derivatives with P–C–N moieties
Prishchenko, Andrey A.,Livantsov, Mikhail V.,Novikova, Olga P.,Livantsova, Ludmila I.,Petrosyan, Valery S.
, (2017)
The various methods of aminomethylation of some PH-acids with proline and their derivatives are investigated. The numerous derivatives of proline and corresponding phosphonates, phosphonites, phosphinates, and phosphorane with proline moieties are presented.
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.
Diastereoselective Synthesis of Fluorine-Containing Pyrrolizidines via Triphenylcarbenium Tetrafluoroborate-Promoted Carbofluorination of N-3-Arylpropargylpyrrolidine-Tethered Tertiary Allylic Alcohols
Yeh, Ming-Chang P.,Chen, Hsiao-Feng,Huang, Yu-Ya,Weng, Yu-Ting
, p. 10892 - 10903 (2015)
Inexpensive and air stable triphenylcarbenium tetrafluoroborate efficiently promoted the carbofluorination of N-arylpropargylpyrrolidines bearing a tertiary allylic alcohol tether at the 2-position of the pyrrolidine ring to provide 1-isobutenyl-2-(fluoro(phenyl)methylenylhexahydro-1H-pyrrolizidines in a stereoselective fashion. When subjected to bis(trifluoromethane)sulfonamide, the same substrates underwent cycloisomerization reaction within minutes to generate 1-isobutenyl-2-benzoylhexahydro-1H-pyrrolizidines with excellent stereoselectivity.
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.
A novel 2 H -azirin-3-amine as a synthon for a sulfur-containing dipeptide segment
Stoykova, Svetlana A.,Linden, Anthony,Heimgartner, Heinz
, p. 14 - 23 (2014)
Starting with tetrahydro-2H-thiopyran-4-carboxylic acid and methyl prolinate, the novel 2H-azirin-3-amine [S]-N-(1-aza-6-thiaspiro[2.5]oct-1-en-2- yl)proline methyl ester was synthesized. In reactions with benzoic acid, thiobenzoic acid and Boc-valine, respectively, its usefulness as a synthon for the dipeptide [S]-N-[(4-aminotetrahydro-2H-thiopyran-4-yl)carbonyl]proline in peptide synthesis was demonstrated.
