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1.
Seiichiro Ogawa Yasushi Uematsu Satoshi Yoshida Naoko Sasaki Tetsuo Suami 《Journal of carbohydrate chemistry》2013,32(3):471-478
Abstract Pseudo-β-D (D-2) and L-fructopyranose (L-2), 1(S) and (1R)-(1,2/-3,4)-4-C-hydroxymethyl-1,2,3,4-cyclohexanetetrol, have been synthesized, starting from optically active endo-adducts of furan and acrylic acid, following the modified procedure used for the preparation of the racemic modification. It has been demonstrated that the D and L-enantiomers are nearly as sweet as D-fructose, and the former is somewhat sweeter than the latter. 相似文献
2.
β,β-Dihalo- and β,β,β-trichloroamines, obtained by Lewis acid-promoted Petasis-type reaction of α,α-dichlorinated and α,α,α-trichlorinated imines or reduction of α,α-dihaloaldimines, were subjected to a reactivity study and turned out to be remarkably stable compounds. In general, only the bases KOtBu and NaOMe cause a 1,2-dehydrochlorination with formation of unsaturated α-chloroimines or unsaturated α,α-dichloroimines. Hydrolysis of the α-chloroimines with aqueous oxalic acid resulted in the formation of the corresponding unsaturated α-chloroketones. The reaction of simple β,β-dihaloamines with NaOMe and KOtBu generated 2-haloprop-2-enylmines and 2,2-dimethoxypropylamines. 相似文献
3.
A simple three-step procedure converted the readily accessible (2-bromo-1,1-difluoroethyl)arenes (2) into α-aryl-α,α-difluoroacetaldehydes (1). Subsequent hydrocyanation, hydrolysis, oxidation and again hydrolysis afforded β-aryl-β,β-difluoro-α-oxopropionic acids (3). Reductive amination transformed the oxoacids 3 into a separable mixture of α-hydroxyacids 11 and racemic β,β-difluoro-β-phenylalanine derivatives (4). Enantiomerically pure β,β-difluorophenylalanine (l-4a) was obtained when α,α-difluoro-α-phenylacet-aldehyde (1a) was condensed with homochiral 1-phenylethylamine, hydrogen cyanide added to the resulting imine, the diastereomeric mixture thus produced hydrolyzed to the carboxamides (15) which were found to be separable by fractional crystallization or chromatography. The pKa values of the β-aryl-β,β-difluoroalanines (4) were measured and biological profile of the latter probed. 3-(4-Chlorophenyl)-3,3-difluoro-2-oxopropionic acid (4c) proved to be a potent (Ki 27 μM) and selective inhibitor of arogenate dehydratase, a key enzyme catalyzing the last step of the phenylalanine biosynthesis. 相似文献
4.
Two isoforms of β-amyloid peptides, Aβ40 and Aβ42, differ from each other only in the last two amino acids, IA, at the end of Aβ42. They, however, differ significantly in their ability in inducing Alzheimer's disease (AD). The rate curves of fibril growth of Aβ40 and Aβ42 and the effects of molecular crowding have been measured in in vitro experiments. These experimental curves, on the other hand, have been fitted in terms of rate constants for elementary reaction steps using rate equation approaches. Several sets of such rate parameters have been reported in the literature. Employing a recently developed stochastic kinetic method, implemented in a browser-based simulator, popsim, we study to reveal the differences in the kinetic behaviors implied by these sets of rate parameters. In particular, the stochastic method is used to distinguish the kinetic behaviors between Aβ40 and Aβ42 isoforms. As a result, we make general comments on the usefulness of these sets of rate parameters. 相似文献
5.
Some new mono- and bis-spiro-β-lactams of benzylisatin were prepared by Staudinger’s ketene-imine [2+2] cycloaddition reaction. The cycloadducts were characterized by spectral data including 1H NMR, 13C NMR, IR and mass spectra. The configuration of benzylisatin and one of mono-spiro-β-lactams (5a) was established by X-ray crystal analysis. 相似文献
6.
L. M. Pevzner 《Russian Journal of General Chemistry》2010,80(7):1249-1257
Chloromethylfuroyl chlorides react with alkyl glycinates and β-alanates to form the corresponding chloromethylfuroyl amides.
The compounds obtained are phosphorylated with triethyl phosphite under the conditions of the Arbuzov reaction to give (diethoxyphosphorylmethylfuroyl
amides. Alkaline hydrolysis of these compounds proceeds only at the carboxy group leading to (diethoxyphosphorylmethyl)furoylglycine
and furoyl-β-alanine. Selectivity of hydrolysis does not depend on the position of carboxamide and diethoxyphosphorylmethyl
groups in the furan ring. 相似文献
7.
K. S. N. Reddy M. J. Eapen P. N. Joshi S. P. Mirajkar V. P. Shiralkar 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(3):197-210
The crystalline isomorphs of-zeolite containing boron or gallium in the framework positions have been synthesized and the products characterized by comparing them with Al- zeolite. Evidence for the presence of B or Ga in the zeolite lattice framework has been confirmed by spectroscopic (XRD, IR and29Si,27Al and11B MASNMR), DTA/TG, ion exchange, sorption and catalytic activity results. Chemical analysis and NMR confirm the absence of any significant amount of Al in the zeolite (SiO2/Al2O3=2000). The XRD pattern of the as-synthesized B- and Ga- compounds matched well with that of Al- zeolite. Lattice B and Ga leads to a change in the X-rayd values. Framework and bridging hydroxyl stretching IR bands of-zeolite are shifted due to incorporation of gallium and boron into the zeolitic framework. MASNMR spectra of11B and29Si also suggest the presence of tetrahedrally coordinated B(III) or Ga(III) ions in the-zeolite framework. B and Ga-zeolites exhibit significant ion exchange capacity and catalytic activity in them-xylene isomerization reaction. The shifts in the IR bands towards higher frequency in B- and lower frequency in Ga-, the observed ion exchange capacities and catalytic properties, indicate the presence of B3+ or Ga3+ ions in the framework of-zeolite. 相似文献
8.
9.
Anand N Shah BA Kapoor M Parshad R Sharma RL Hundal MS Pannu AP Bharatam PV Taneja SC 《The Journal of organic chemistry》2011,76(15):5999-6006
The facile synthesis of the stabilized axial and equatorial conformers of spiro-β-lactams was achieved via entrapment of cyclohexanone imines (Schiff bases) with acetoxyacetyl chloride in a [2 + 2]-cycloaddition reaction followed by their kinetic resolution. The immobilization of the racemic substrates on an inert solid support significantly reduced the reaction time and improved the enantioselectivity of conformers during kinetic resolution. The mechanism of the formation of the spiro-β-lactams was explored using B3LYP/6-31+G* level quantum chemical calculations. 相似文献
10.
Yu-Gui Li Yun-Shan Liu Fang-Ming Miao Xiao-Lan Liu Jin-Hong Cao Wei Zhou 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):57-60
Abstract Twenty-three new α -aryl-β -nitroalkylphosphinates 3a - g were synthesized in high yields under very mild conditions. Compounds 3 consist of two pairs of diastereomeric isomers (A) and (B) 相似文献
11.
The utility of organoboranes in the synthesis of a wide variety of functional groups is now well established.1 There have been, however, only a limited number of reports where an organoborane containing a β-functionalized carbon was utilized in organic synthesis. Part of the reason for this is the difficulty in preparing β-functional organoboranes and their tendency to undergo elimination under a variety of reaction conditions.2 Those β-functionalized organoboranes utilized synthetically, which we could find in the literature are the β-ethoxy3, 1, and β-carboethoxyvinyl-boranes4, 2, of Zweifel and coworkers and the trans-β-tert-butyldimethylsilyloxy organoborane, 3, of Corey and Ravindranathan,5 who proposed this system as a potential precursor to prostanoids. 相似文献
12.
13.
《Tetrahedron letters》1986,27(18):2027-2030
A general method for the synthesis of Z-β-siloxyacrylonitriles from isoxazoles is reported. Their dienophilic activity is also described. 相似文献
14.
Pandey SK Jogdand GF Oliveira JC Mata RA Rajamohanan PR Ramana CV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(46):12946-12954
The synthesis of homochiral homo-oligomers of cis- and trans-3-aminotetrahydrofuran-2-carboxylic acids (parent cis- and trans-furanoid-β-amino acids, referred to as "cis-/trans-FAA") has been carried out to understand their secondary structures and their dependence on the ring heteroatom. The oligomers of two diastereomers have been shown to have a distinct left-handed helicity. The cis-FAA homo-oligomers show a 14-helix structure, in contrast to the homo-oligomers of cis-ACPC, which adopt a sheet like structure. The trans-FAA homo-oligomers were found to adopt a 12-helix structure, the same trend found in trans-ACPC homo-oligomers. With the help of ab initio calculations, the structural features of cis-ACPC and cis-FAA hexamers were compared. We believe that the more compact packing of the cis-FAA hexapeptide should be due to a more favorable interaction between the ring and the backbone amide hydrogen. 相似文献
15.
Xizhao Ding Mengke Zheng Jiamin Lu Xingyi Zhu 《Journal of inclusion phenomena and macrocyclic chemistry》2018,91(1-2):17-24
This study aimed to investigate the effect of hydroxypropyl methylcellulose on the complexation of fenofibrate and hydroxypropyl-β-cyclodextrin (HP-β-CD). Initially, phase solubility studies with an excess amount of drug in the HP-β-CD solutions with and without hydroxypropyl methylcellulose (HPMC) were investigated. Both of the binary and ternary complexes were prepared by ball-milling. The complexes were characterized by Fourier transform infrared spectroscopy (FI-IR), X-ray powder diffraction (XPRD), differential scanning calorimetry (DSC) and nuclear magnetic resonance spectroscopy (1H-NMR). The AL type phase-solubility diagram revealed that the complexes of fenofibrate and HP-β-CD were formed with molecular ratio of 1:1. The results of FT-IR, XPRD, DSC and 1H NMR analysis show the formulation of inclusion complexes. In conclusion, the interaction occurrs between fenofibrate and HP-β-CD in the complexes, and the existence of HPMC effectively improves the complexation efficiency and stability constant. The in vitro dissolution test suggests ternary complex is superior to binary complex in terms of the release of fenofibrate. 相似文献
16.
Cécile Donzé Enrico Rizzarelli Graziella Vecchio 《Journal of inclusion phenomena and macrocyclic chemistry》1998,31(1):27-41
-cyclodextrins functionalized by D or L-tryptophan were synthesised. NMR, circular dichroism and fluorescence investigations were carried out showing the clear intramolecular inclusion of the tryptophan in the cyclodextrin cavity. The derivatives act as a fluorescent sensor which is useful for detecting organic species in solution. Furthermore, derivatives L and D show different sensitivity with regard to their interaction with a guest. The difference might be due to the disposition of the indole with respect to the cavity of the cyclodextrin, induced by the chirality of the tryptophan. 相似文献
17.
Bohumil Dolensky 《Journal of fluorine chemistry》2003,123(1):95-99
Nucleophilic attack of azide on 2-bromo-3-fluoro-3-(1-trityl-1H-imidazol-4-yl)-propan-1-ol (1a) in aprotic solvent occurs on the 2-position to give the 2-azido derivative (2a). Reduction of azide and removal of the trityl group produces β-fluorohistidinol (6a). Elimination of HBr from 1a followed by “FBr” addition to the resulting double bond gives 2-bromo-3,3-difluoro-3-(1-trityl-1H-imidazol-4-yl)-propan-1-ol (1b). Nucleophilic attack of azide followed by reduction and removal of the trityl group, as for the preparation of 6a, gives β,β-difluorohistidinol (6b). Initial attempts, under a variety of conditions, to oxidize the fluorinated histidinol precursors to carboxylic acids have not been successful. 相似文献
18.
An efficient method for the synthesis of N-Cbz-β-aminoalkanesulfonamides was described.N-Cbz-β-aminoalkanesulfonamides were readily prepared in good yields from a variety of amino alcohols,including optically active ones,via N-Cbz protection with benzyl chloroformate,Mitsunobu esterification reaction with thiolacetic acid,N-chlorosuccinimide oxidation,and ammonolysis process. 相似文献
19.
Nataly I. Svintsitskaya Аlbina V. Dogadina Galina L. Starova Rostislav Е. Trifonov 《Tetrahedron letters》2014
Addition of 5-substituted tetrazoles to dimethyl [(N,N-diisopropylamino)ethynyl]phosphonate proceeds regio- and stereoselectively to yield (Z)-[2-diisopropylamino-2-(tetrazolyl)vinyl]phosphonic acid dimethyl esters. The Z-configuration of the products was confirmed by 1Н NMR spectroscopy and single-crystal X-ray diffraction. The reactions occur via nucleophilic attack of tetrazole involving predominantly the N-1 atom of the tetrazole ring. 相似文献