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1.
The synthesis of α-amino-β-keto-esters (β-oxo dipeptides) was studied. Corresponding α-amino-β-ketoesters were prepared from BOC-(L)-Valine and BOC-(L)-isoleucine by coupling with (D,L)-threonine hydrochloride and oxidation
with Dess-Martin periodinane (DMP) with a total yield of 48% and 38%, respectively.
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Translated from Chemistry Online, 2007, 70(10): 793–796 [译自: 化学通报] 相似文献
2.
Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect… 相似文献
3.
Nicolas Marquet 《Tetrahedron》2008,64(1):75-83
A series of novel β-hydroxy-β-bis(trifluoromethyl)-imines (2a-j) and di(β-hydroxy-β-bis(trifluoromethyl))-diimines (3a-f) were prepared in moderate to good yields via a simple two-step approach: first, β-hydroxy-β-bis(trifluoromethyl)-ketones (1a-c) were obtained by a catalyst-free aldol reaction between liquid hexafluoroacetone sesquihydrate and ketones (acetone, acetophenone, and pinacolone, respectively); then, condensation of the latter fluorinated β-ketols 1a-c with primary amines or diamines was achieved in the presence of Lewis (montmorillonite, InBr3, La(OTf)3) or Brönsted (PTSA) acid catalysts. The molecular structures of mono- and di-β-hydroxy-β-bis(trifluoromethyl)-(di)imines 2e,h and 3a,f were determined and found to exhibit strong intramolecular (R)N?H-O hydrogen bonding. 相似文献
4.
Hua-Hua Wang Yi-Yu Jiang Mian HR Mahmood Hai-Yang Liu Herman H.Y. Sung Ian D. Williams Chi K. Chang 《中国化学快报》2015,26(5):529-533
Tetrakis(alloxycarbonyl)porphyrin and its β-octafluoro-substituted derivatives were synthesized via Lindsey method and transformed to their zinc complexes.Single crystal X-ray structures of corresponding Zn(Ⅱ) porphyrins revealed that β-octafluorination will give more compactness of porphyrin moieties in the crystal structure owing to the hydrogen bonding interactions involving β-fluorine atoms.An unusual six-coordinated Zn(Ⅱ) was found via intramolecular coordination of oxygen atom of meso-substituents with central Zn(Ⅱ). 相似文献
5.
6.
N. V. Petrochenkova A. G. Mirochnik A. S. Shishov A. A. Sergeev S. S. Voznesenskii 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(1):158-162
Interaction between Eu(III) tris(β-diketonates) and ammonia vapors increases the luminescence of Eu(III). A mechanism for the effect of analyte molecules on the intensification of Eu(III) luminescence is proposed. The mechanism includes the displacement of water molecules from the coordination sphere of europium(III). 相似文献
7.
Long Chen Peng Wang Yanmo Chen Yu Zhang Meifang Zhu 《Frontiers of Chemistry in China》2008,3(4):445-450
In this paper, the crystallization behavior, thermal degradation properties, rheological behavior and the spinnability of
poly(β-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fiber were studied. Experimental results indicated that the spherulite growth rate of PHBV was very
slow and its size was very large. PHBV began to degrade above 170°C. The flowing curve indicated that the processing temperature
and the residential time had important effects on PHBV melts. When the equipment of melting spinning was improved and processing
conditions were strictly controlled, the mechanical properties of the PHBV filament can comply with the requirements of the
American Pharmacopoeia.
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Translated from Journal of Donghua University (Natural Science Edition), 2007, 33(4): 425–430 相似文献
8.
Maurer C Pittenauer E Du VA Allmaier G Schubert U 《Dalton transactions (Cambridge, England : 2003)》2012,41(8):2346-2353
Reaction of Ti(OiPr)(4) with various bis(β-diketones) and bis(β-ketoesters) (LH(2)) results in the formation of dimeric complexes [Ti(OiPr)(2)L](2), where each metal centre is coordinated by two terminal OiPr ligands and two bridging β-diketonate or β-ketoesterate groups (L). Macrocycles containing two M(OiPr)(2) moieties are thus formed. Reaction of Zr(OiPr)(4) with the same bis(β-diketones) and bis(β-ketoesters) results in different compounds, depending on the organic spacer connecting the two functional groups. With shorter spacers, the compounds [ZrL(OiPr)(2)](2)·2iPrOH are obtained, with the same structures as the corresponding titanium complexes. With longer spacers, however, complexes with a higher degree of substitution are formed, such as (ZrL(2))(2) and Zr(2)L(3)(OiPr)(2)·2iPrOH. The molecular weight and structure of all compounds was elucidated by ESI-MS. MS/MS of the corresponding [M+Na](+) precursor ions confirmed the proposed structures based on structure-specific product ions. Solution NMR experiments and DFT calculations additionally supported the proposed structures. 相似文献
9.
Previously unknown (methyl--cyanoethyl)tri-, -tetra-, and -pentacyclosiloxanes were prepared by oxygen-halogen exchange between silicon and tin. The 29Si NMR spectra of the products were measured and interpreted. 相似文献
10.
《Journal of Coordination Chemistry》2012,65(1-2):57-63
Abstract The reaction of bis(β-alaninato)copper(II) with formaldehyde results in the formation of blue crystals of aquabis(N,N-dimethyl-β-alaninato)copper(II) hexahydrate, [Cu(C5H10NO2)2(OH2)].6H2O which crystallize in the monoclinic space group C2/c with unit cell dimensions a = 20.799(2), b = 8.112(1), c = 23.639(1)Å, β = 96.50(1)° and Z = 8. The structure has been refined to final R = 0.047 and Rw = 0.053 for 1690 reflections with I ≥ 2.55σ(I). 相似文献
11.
The paper reports on the dependence of the absorbance and luminescent intensity from pH of novel poly(oxyethylene phosphate)
tris(β-diketonate) europium (III) complexes. The photophysical data obtained allow some preliminary assumptions about the
nature of this phenomenon. Increase in luminescent efficiency is a consequence of enhanced efficiency of energy transfer caused
by structural changes in complexes after water deprotonation. Remarkable change has been observed in photophysical properties
of the polymer complexes by studying the fluorescent emission and excitation spectra and absorption recorded at various pH
both in solution and in the solid state. Some of the complexes derivative of the dibenzoylmethane (DBM) show more than hundred
times increase in the luminescence after alkalization. The pH value, at which the maximum luminescent efficiency appears,
depends on the type of the fourth ligand. The difference between luminescent efficiency of the complexes in alkaline and neutral
environment depends on the β-diketonate ligands and on polymer type as well.
相似文献
12.
Zemmouri R Kajjout M Castanet Y Eddarir S Rolando C 《The Journal of organic chemistry》2011,76(19):7691-7698
We report here the stereoconvergent formylation of (E/Z)-β-bromo-β-fluorostyrene mixtures with carbon monoxide and sodium formate catalyzed by palladium. Optimization of reaction conditions leads to the corresponding pure (Z)-α-fluorocinnamaldehydes in good yields. The reaction was extended to styrenes bearing electro-attracting or electro-donating groups. The obtained α-fluoroaldehydes were smoothly reduced to the corresponding (Z)-β-fluorocinnamic alcohol by NaBH(4). The reaction could be performed on functionalized substrates as demonstrated by the access to the glucoside of β-fluoroconiferyl alcohol, (Z)-β-fluoroconiferin, a strong inhibitor of lignin polymerization. 相似文献
13.
8β-hydroxyeremophil-7(11)-ene-12,8α(4β,6α)-diolide was isolated from the Ligularia intermedia and char- acterized by MS, multi NMR and X-ray single crystal diffraction. Its crystal structure was determined as in a orthorhombic type, with space group P212121 with a=6.8519(5), b=10.7191(8), c=18.5942(14) oA, V =1365.67(18) oA3, Z=4, and the calculated density is 1.354 mg/m3. F(000)=592, μ=0.101 mm-1. 相似文献
14.
本文报道了5种Cr(β-dik)Cl_2(β-pic)_2型混配配合物的合成及其电子光谱、红外光谱、热分析的表征工作。 相似文献
15.
Soundar Divakar 《Journal of inclusion phenomena and macrocyclic chemistry》1994,17(2):119-125
Distances of glucose protons in-cyclodextrin (BCD) from copper(II) in copper(II)--cyclodextrin have been determined from1H NMR spin-lattice relaxation time (T
1) measurements for the first time. Very lowT
1p
/T
2p
values indicated the dipolar mechanism to be the most dominant one in determining the paramagnetic contribution to relaxation. The distances of copper(II) from BCD glucose protons indicated copper(II) to be present almost in the centre, inside the cavity in the same plane as H-1 and H-4. An average distance of about 5.0–5.9 Å was obtained for copper(II) from the H-2, H-3, H-1, H-4 and H-6 a and b protons in BCD. 相似文献
16.
V. Zia D. Vander Velde V. J. Stella 《Journal of inclusion phenomena and macrocyclic chemistry》2014,79(3-4):503-512
The thermodynamics of binding of various neutral, cationic and anionic substrates to β-cyclodextrin, a hydroxylpropyl-β-cyclodextrin (HP4M-β-CD) and three sulfobutyl-β-cyclodextrins with varying degrees of total substitution (SBE1M-β-CD, SBE7M-β-CD, and SBE12M-β-CD) were determined by estimating binding constants, using a UV spectrophotometric technique, and temperature variation. linear free energy relation (LFER) plots and enthalpy–entropy Compensation (EEC) plots provided insight into the mechanisms of complexation as did carbon T 1 relaxation times using NMR. LFER plots for charged molecules with HP4M-β-CD deviate from the neutral substrates suggesting differences in interaction modes. LFER plots for SBE7M-β-CD show that cationic substrates surprisingly fall within the same linear relationship for neutral substrates while anionic substrates deviate. The EEC plots for HP4M-β-CD show the largest loss of motion and degree of desolvation upon complexation. The interaction with SBE1M-β-CD was similar to that for β-CD. SBE7M-β-CD, and SBE12M-β-CD EEC plots are similar with the least loss of motion upon complex formation, suggesting a more organized and less flexible structure. This is supported by the T 1 relaxation times for SBE1M-β-CD, SBE7M-β-CD, and SBE12M-β-CD, which show a critical distance at which the mobility of the side chain is reduced to form an extended cavity. No such evidence was seen with HP4M-β-CD, although the effect of varying of hydroxypropyl substitution was not studied. 相似文献
17.
淀粉样多肽(amyloid-βpeptide,Aβ)聚集是引起阿尔兹海默症(Alzheimer's disease,AD)的主要原因。开发Aβ聚集抑制剂是治疗AD的最有效手段之一。利用噬菌体展示技术筛选出来的Z_(Aβ3)蛋白质能够有效抑制Aβ聚集,但Z_(Aβ3)和Aβ之间的作用区域和关键氨基酸残基尚不清楚。针对此问题,本研究利用分子动力学模拟、MM-PBSA自由能计算和分解方法研究了Z_(Aβ3)-Aβ_(16–40)复合物之间的相互作用机制。结果表明,Z_(Aβ3)的β-股和Aβ_(16–40)之间的亲和作用占主导,而Z_(Aβ3)的α-螺旋贡献很小。利用分子力学-帕松波尔茨曼溶剂可及化表面积方法(MM-PBSA)自由能分解发现Z_(Aβ3)的热点残基为E15、I16、V17、Y18、L19、P20、N21和L22,而Aβ_(16–40)的热点残基为F19、F20、A21、E22、D23、K28、I31、I32、G33、L34、M35、V36、G38和V40。Z_(Aβ3)通过将发夹型Aβ单体包埋在α-螺旋围成的疏水性腔体内来阻碍Aβ聚集。这种结合模式为设计高效的Aβ蛋白质类抑制剂提供了三个基本要素:高亲和性的结合片段(β-股)、附属结构(α-螺旋)和通过二硫键形成的稳定构象。高亲和性结合片段能竞争性地与Aβ单体结合,附属结构α-螺旋可以阻碍其它Aβ单体靠近,而稳定的构象是上述两种要素发挥作用的基础,三者协同作用可以有效地抑制Aβ聚集。 相似文献
18.
Cheng-Zhu Liao Xiao-Long Feng Jun-Hua Yao Jiwen Cai 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1215-1216
In the crystal structure of the title compound, 2C3H8NO2+·C12H8O6S22−, N—H⃛O hydrogen bonds formed between the amino H atoms and the sulfonate O atoms give rise to the assembly of cationic β-alaninium dimers and centrosymmetric biphenyl-4,4′-disulfonate anions into an extended two-dimensional layer. The resulting hydrogen-bonded ribbons can be described as C(6)R(12) according to graph-set notation. C—H⃛O hydrogen bonds between adjacent sheets further extend the structure into a three-dimensional arrangement. 相似文献
19.
Conclusions ,-Bis(trifluoromethyl)glycidic ester is far more active than ,-dimethylglycidic ester and is opened by amines on the side of the -carbon atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8 pp. 1529–1530, August, 1964 相似文献
20.
Various complexes have been prepared by the template condensation of -amino acids with formaldehyde or acetaldehyde in the presence of metal ions(1–5). In particular, glycine has received much attention(1–4). For example, (3N, 7N-1,3,5,7-tetraazabicyclo[3.3.1]nonyl)-diacetato nickel(II) (1) has been prepared by condensing bis(glycinato)nickel(II) dihydrate with formaldehyde and ammonia at pH 8.54. More recently5, complex (2) has been prepared by condensing bis(L-alaninato)copper(II) with formaldehyde and ammonia. These reactions are interesting for the following reasons:
Here we describe the preparation of (3N, 7N-1,3,5,7-tetraazabicyclo[3.3.1]nonyl)di-3-propionato copper(II), (4) from the condensation of bis(-alaninato)copper(II) hexahydrate with formaldehyde and ammonia. 相似文献
(i) | Products (1) and (2) have their amino acidato chelate ringscis with respect to each other, which implies that during the condensation process they must have undergone conversion from the initialtrans arrangement of the amino acid units(6,7) to acis arrangement; |
(ii) | Whereas the copper(II) analogue of (1) is formed in the reaction of bis(glycinato)copper(II) monohydrate with formaldehyde and ammonia(4), the nickel(II) analogue of (2) does not result in the reaction of bis(L-alaninato)nickel(II) with formaldehyde and ammonia(5); |
(iii) | Bis(DL-alaninato)copper(II) monohydrate does not yield product similar to (2) on condensation with formaldehyde in the presence of ammonia at pH 8.5, but instead yields another product (3)(3, 5). |