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1.
Experimental and Theoretical Studies on the Rearrangement of 2‐Oxoazepane α,α‐Amino Acids into 2′‐Oxopiperidine β2,3,3‐Amino Acids: An Example of Intramolecular Catalysis
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Dr. Diego Núñez‐Villanueva Dr. M. Ángeles Bonache Laura Lozano Dr. Lourdes Infantes Prof. José Elguero Prof. Ibon Alkorta Prof. M. Teresa García‐López Dr. Rosario González‐Muñiz Dr. Mercedes Martín‐Martínez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2489-2500
Enantiopure β‐amino acids represent interesting scaffolds for peptidomimetics, foldamers and bioactive compounds. However, the synthesis of highly substituted analogues is still a major challenge. Herein, we describe the spontaneous rearrangement of 4‐carboxy‐2‐oxoazepane α,α‐amino acids to lead to 2′‐oxopiperidine‐containing β2,3,3‐amino acids, upon basic or acid hydrolysis of the 2‐oxoazepane α,α‐amino acid ester. Under acidic conditions, a totally stereoselective synthetic route has been developed. The reordering process involved the spontaneous breakdown of an amide bond, which typically requires strong conditions, and the formation of a new bond leading to the six‐membered heterocycle. A quantum mechanical study was carried out to obtain insight into the remarkable ease of this rearrangement, which occurs at room temperature, either in solution or upon storage of the 4‐carboxylic acid substituted 2‐oxoazepane derivatives. This theoretical study suggests that the rearrangement process occurs through a concerted mechanism, in which the energy of the transition states can be lowered by the participation of a catalytic water molecule. Interestingly, it also suggested a role for the carboxylic acid at position 4 of the 2‐oxoazepane ring, which facilitates this rearrangement, participating directly in the intramolecular catalysis. 相似文献
2.
Dong‐Cheol Shin Yun‐Hi Kim Hong You Jae Gyu Jin Soon‐Ki Kwon 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5636-5646
A poly(p‐phenylenevinylene) (PPV) derivative containing a bulky (2,2‐diphenylvinyl)phenyl group in the side chain, EHDVP‐PPV, was synthesized by Gilch route. The reduced tolane‐bisbenzyl (TBB) defects, as well as the structure of the polymer, was confirmed by various spectroscopic methods. The intramolecular energy transfer from the (2,2‐diphenylvinyl)phenyl side group to the PPV backbone was studied by UV‐vis and photoluminescence (PL) of the obtained polymer and model compound. The polymer film showed maximum absorption and emission peaks at 454 and 546 nm, respectively, and high PL efficiency of 57%. A yellow electroluminescence (λmax = 548 nm) was obtained with intensities of 6479 cd/m2 when the light‐emitting diodes of ITO/PEDOT/EHDVP‐PPV/LiF/Al were fabricated. The maximum power efficiency of the devices was 0.729 lm/W with a turn‐on voltage of 3.6 V. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5636–5646, 2004 相似文献
3.
The First Intramolecular Charge Transfer Transition Based on 2-Ureido-4[1H]-pyrimidinone Binding Module 总被引:1,自引:0,他引:1
The first intramolecular charge transfer transition based on 2-ureido-4[1H]-pyrimidinone binding module was reported. 相似文献
4.
It has been shown that the kinetics of intramolecular processes and time-resolved spectra with allowance for the quantum beats of the resonant states of isomers or isolated subsystems of levels of one isomeric form can be described with the use of a molecular model interpreting the effect of beats as a nonradiative transition. We have obtained an expression for the nonradiative transition probability, which is directly proportional to the beat frequency and depends oscillatorily on time, thus modeling the effect of beats. The parameter of the molecular system model is the beat frequency directly related to the parameter characterizing the intramolecular interisomeric interactions (the corresponding nondiagonal element of the energy matrix) rather than the value of the nonradiative transition probability. The character of the change in the level populations and, accordingly, in the band intensities in the spectra in the proposed model is in good agreement with the experiment, including the fine structure of the time dependences — oscillations of the line intensities. In analyzing the temporal experiment with a high resolution, it is necessary to take into account the instrument function leading to quantitative and qualitative changes in the time dependences. The traditional model of nonradiative transitions with a constant probability value has a very limited range of applicability — very high beat frequencies compared to the probability of optical transitions. 相似文献
5.
I. V. Ukrainets L. V. Sidorenko O. V. Gorokhova N. A. Jaradat 《Chemistry of Heterocyclic Compounds》2006,42(4):475-487
Various methods of synthesizing amides of 2-hydroxy-4-imino-1,4-dihydroquinoline-3-carboxylic acids have been studied. Results
of investigations on the antitubercular and antiinflammatory activity of the obtained compounds are discussed.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 542–555, April, 2006. 相似文献
6.
Donald Craig 《Tetrahedron: Asymmetry》1991,2(12):1177-1180
The synthesis and thermally-induced intramolecular Diels-Alder (IMDA) reaction of (S)s-(+)-S-[(1E,7E)-1,7,9-decatrienyl]-S-phenyl-N-(p-tolylsulphonyl)sulphoximine 4 is described. A model is proposed for the cis-selectivity of the cycloaddition based on previous results from the reactions of sulphonyl-substituted trienes. The stereochemistry of the major cis-fused cycloadduct is determined by single-crystal X-ray analysis of that obtained from reaction of racemic 4. 相似文献
7.
V. I. Saloutin I. T. Bazyl' Z. E. Skryabina P. N. Kondrat'ev O. N. Chupakhin 《Russian Chemical Bulletin》1994,43(2):279-282
Reactions of pentafluorobenzoylpyruvic acid with amines afford the respective enamines. The intramolecular cyclization of the latter results inN-substituted 4-quinolone-2-carboxylic acids. Ammonia and triethylamine favor the cyclization of pentafluorobenzoylpyruvic acid to 2-carboxychromone.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 299–302, February, 1994. 相似文献
8.
An O-bonded sulphito complex, Rh(OH2)5(OSO2H)2+, is reversibly formed in the stoppedflow time scale when Rh(OH2)
6
3+
and SO2/HSO
3
−
buffer (1 <pH< 3) are allowed to react. For Rh(OH2)5OH2++ SO2 □ Rh(OH2)5(OSO2H)2+ (k1/k-1), k1 = (2.2 ±0.2) × 103 dm3 mol−1 s−1, k−1 = 0.58 ±0.16 s−1 (25°C,I = 0.5 mol dm−3). The protonated O-sulphito complex is a moderate acid (K
d
= 3 × 10−4 mol dm−3, 25°C, I= 0.5 mol dm−3). This complex undergoes (O, O) chelation by the bound bisulphite withk= 1.4 × 10−3 s−1 (31°C) to Rh(OH2)4(O2SO)+ and the chelated sulphito complex takes up another HSO
3
−
in a fast equilibrium step to yield Rh(OH2)3(O2SO)(OSO2H) which further undergoes intramolecular ligand isomerisation to the S-bonded sulphito complex: Rh(OH2)3(O2SO)(OSO2)- → Rh(OH2)3(O2SO)(SO3)− (k
iso
= 3 × 10−4 s−1, 31°C). A dinuclear (μ-O, O) sulphite-bridged complex, Na4[Rh2(μ-OH)2(OH)2(μ-OS(O)O)(O2SO)(SO3) (OH2)]5H2O with (O, O) chelated and S-bonded sulphites has been isolated and characterized. This complex is sparingly soluble in water
and most organic solvents and very stable to acid-catalysed decomposition 相似文献
9.
T. González-Lezana G. Delgado-Barrio P. Villarreal F.X. Gadéa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):227-232
The stabilization method is applied to the case of interacting resonances in the photo-dissociation of van der Waals clusters
composed by a rare gas atom bound to a dihalogen molecule. The study of an illustrative two-dimensional model consisting in
a T-shaped NeI2 molecule shows the adequacy of the method whenever the projection of the stabilization wave functions on the assumed prepared
initial state is accounted for. The agreement of the fragmentation cross-sections with some previous results using the effective
resolvent method and accurate close-coupling calculations is excellent. The method reveals its utility as a complementary
tool since allows, through the analysis of the stabilization wave function in terms of zero-order levels, a precise characterization
of the resonant states involved.
Received 5 April 2002 / Received in final form 24 May 2002 Published online 19 July 2002 相似文献
10.
N. A. Borisevich D. A. Kazberuk S. V. Mel'nichuk S. A. Tikhomirov G. B. Tolstorozhev 《Journal of Applied Spectroscopy》1995,62(3):441-446
Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70 F. Skaryna Ave, Minsk 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 3, pp. 49–55, May–June, 1995. 相似文献