首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Wang Q  Wang Y  Kurosu M 《Organic letters》2012,14(13):3372-3375
An Oxyma derivative, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl 2-cyano-2-(hydroxyimino)acetate (2), displayed remarkable physicochemical properties as a peptide-coupling additive for peptide-forming reactions in water. Short peptides to oligopeptides could be synthesized by using 2, EDCI, and NaHCO(3) in water without measurable racemization. Significantly, a simple basic and acidic aqueous workup procedure can remove all reagents utilized in the reactions to afford only coupling products in consistently excellent yields.  相似文献   

2.
Racemic 2-amino-3-(heteroaryl)propanoic acids (1), mostly with a furan or thiophene nucleus as a heteroaryl group, were synthesized in 48-94% yield by the reduction of 3-(heteroaryl)-2-(hydroxyimino)propanoic acids (5) with zinc dust and formic acid in the presence of a catalytic amount of iron dust at 60 degrees C for 2 h. Under these conditions, unfavorable hydrogenolysis of bromine on the thiophene nucleus does not occur. Traditional N-formylation of the prepared 3-(heteroaryl)alanine (1) with a mixture of formic acid and acetic anhydride afforded 2-(formylamino)-3-(heteroaryl)propanoic acids (6) in 51-95% yield.  相似文献   

3.
The reaction between methyl or ethyl esters of 1, 2-benzisoxazole-3-acetic acid and iso-amyl nitrite is reported. The main product is identified as 4-(2′-hydroxyphenyl)furazan-3-carboxylic acid ( 4 ) by chemical and X-ray crystal structure analyses. The synthesis of esters of E- and Z-α-(hydroxyimino)-1, 2-benzisoxazole-3-acetic acid is also reported.  相似文献   

4.
1H and 13C NMR spectra of the oxocarboxylic acid oximes 2-hydroxyiminopropanoic acid (1), 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (2) and 2-cyano-2-(hydroxyimino)acetic acid (3) were measured in DMSO-d6, D2O and acetone-d6 solutions. The data indicate the presence of hydrogen bonding in 1 and 2 and a strong electron-withdrawing effect due to the cyano group in 3. The effect of intra- and intermolecular hydrogen bonding on the hydrogen and carbon chemical shifts in these molecules was studied theoretically. Total energy calculations of the stability of various hydrogen-bonded species, in addition to equilibrium parameters and chemical shifts, were calculated using ab initio methods (RHF, MP2) and density functional theory (B3LYP), implemented in the Gaussian 98 software package. The gauge-including atomic orbital (GIAO) method was used to predict magnetic shielding constants. Chemical shift calculations for the most stable species agree fairly well with the observed data, especially for the hydroxyl protons. Substituents adjacent to the alpha-carbon show some influence of the oximic and carboxyl groups on the 13C chemical shifts, as expected for groups with different polar and anisotropic character.  相似文献   

5.
The four stereoisomers of 3-isopropyl-5-methoxy-6-ketoheptanoic acid methylester and those of 2-methoxy-4-isopropylhexandioic acid methylester were synthesized from R(?)- and S(+)-carvone. The combined data given provide a basis for specific enantiomer assignment to natural product degradation materials.  相似文献   

6.
A novel monoterpene, (1S, 2S, 6S)-(+)-1,6-epoxy-4(8)-p-menthen-2-ol, was isolated from an elicitor-treated cell culture of Cupressus lusitanica (Mexican cypress). Ten known monoterpenes--limonene, myrcene, beta-ocimene, sabinene, terpinolene, 4-terpineol, alpha-terpineol, 4(8)-p-menthen-1,2-diol, 4-hydroxyphellandric acid methylester and beta-thujaplicin methylether--were also identified. Regioselective metabolisms of monoterpenes were observed in this culture.  相似文献   

7.
Condensation reactions of comenaldehyde methyl ether (I) with malonic acid, ethyl cyanoacetate, and cyanoacetamide to give β-(5-methoxy-4H-pyran-4-on-2-yl)acrylic acid (II), ethyl 2-cyano-3-(5-methoxy-4H-pyran-4-on-2-yl)propenoate (III), and 2-cyano-3-(5-methoxy-4H-pyran-4-on-2-yl)propenamide (IV), respectively, are described. Ultraviolet absorption spectra for 2-hydroxymethyl-5-methoxy-4H-pyran-4-one, I and II are presented.  相似文献   

8.
A new class of 1,3,5-triazinyloxyimino derivatives were prepared, characterized and tested for reactivity in solution peptide synthesis. The new triazinyloxyimino derivatives failed to activate the carboxyl group during formation of peptide bonds, but gave the corresponding N-triazinyl amino acid derivatives as a major product. The oxyma (ethyl 2-cyano-2-(hydroxyimino)acetate) uronium salt was superior to other uronium salts in terms of racemization, while 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT, 9) gave the best results.  相似文献   

9.
2-Dialkylamino-4-methoxy-6-trinitromethyl-1,3,5-triazines reacted with triphenylphosphine in toluene in the presence of primary aliphatic alcohols as proton donors to give the corresponding 6-[hydroxyimino (nitro)methyl)-1,3,5-triazines. Analogous reactions in the presence of prop-2-yn-1-ol at elevated temperature resulted in the formation of [3 + 2]-dipolar cycloaddition products, 3-(1,3,5-triazinyl)-5-hydroxymethylisoxazoles.  相似文献   

10.
Acid-catalyzed methanolysis of N-hydroxy-α-oxobenzeneethanimidoyl chloride ( 1 ), a 2-(hydroxyimino)-1-phenylethan-1-one derivative obtained in one step from acetophenone, leads to a constant ratio of methyl α-oxobenzeneacetate ( 2 ) and methyl α-(hydroxyimino)benzeneacetate ( 3 ). 13C(α) Labelled [13C]- 1 affords 13C(α) labelled [13C]- 3 , thus discarding the hypothesis of its formation via 1,2-arene migration. The reported sequence opens a novel approach to phenylglyoxylic and mandelic acid esters (=α-oxobenzeneacetic and α-hydroxybenzeneacetic acid esters), from acetophenone. The molecular structures of 1 and 3 were determined by X-ray structure analysis and compared with previously reported crystallographic data of α-oxo-oximes (=α-(hydroxyimino) ketones) 4 and 6 – 8 . The unique stereoelectronic characteristics of the α-oxo-oxime moiety are discussed. All α-oxo-oximes share the following structural characteristics: (E)-configuration of the oxime C=N−OH bond (i.e. OH and C=O trans), the s-trans conformation of the oxo and imino moieties about the C(α)-C(=NOH) single bond, and intermolecular H-bonding. They differ from the isostructural β-diketone enols by the absence of resonance-assisted intramolecular H-bonding.  相似文献   

11.
N-[(Dialkylamino)(thiocarbonyl)]benzimidoyl chlorides react with α-amino acid esters under formation of the corresponding N-[(dialkylamino)(thiocarbonyl)]benzamidines. Derivatives with glycine ethylester, HL(GlyOEt), cysteine methylester and S-benzyl protected cysteine ethylester, HL(S-Bzl-CysOEt), were prepared and isolated in crystalline form. The reaction with cysteine methylester yields the corresponding sulfur-bridged dimeric compound {HL(CysOMe)}2.  相似文献   

12.
The esterifications of 9-(hydroxyimino)-4-methyl-8,9-dihydrofuro[2,3-h]chromen-2-one (4) with acid chlorides afforded normal oxime-esters 3a-e in 35-78% yields in presence of excessive 4-dimethylaminopyridine as the acid scavenger, whereas the reactions gave unexpected 8-substituted products N-(8-chloro-4-methyl-2-oxo-2H-furo-[2,3-h]chromen-9-yl)amides (5a-c) and 4-methyl-2,9-dioxo-8,9-dihydro-2H-furo[2,3-h]chromen-8-ylcarboxyloates (6d-e) by using excessive acid chlorides. The structures of 10 new compounds were determined by 1H NMR, 13C NMR, MS and HRMS, and the possible mechanism for the formation of unexpected products 5a--c and 6d-e was also proposed.  相似文献   

13.
Alkylation products were obtained from ethyl 2-(hydroxyimino)-7-methyl-3-oxo-5-aryl-2,3- dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-6-carboxylates at the treatment with alkyl halides, dimethyl sulfate, and diazomethane. Diazomethane alkylated the initial substrate at the oxygen atom of the carbonyl group of the thiazolidine fragment, the other reagents, at the oxygen atom of the hydroxyimino group.  相似文献   

14.
A new functionalized gemini surfactant, 3,3′-[2-(hydroxyimino)propane-1,3-diyl]bis(1-dodecyl-1H-imidazol-3-ium) dichloride, and its non-micelle-forming methyl analog, were synthesized. Nucleophilicity of the oximate group in these compounds in the decomposition of 4-nitrophenyl esters derived from phosphorus and sulfur acids follows Brønsted relations for monomeric functionalized surfactants and non-micelle-forming oximes. As compared to the single-chained analog, the gemini surfactant ensured the same observed rate of substrate decomposition at lower concentration and lower pH. Micellar effects of the gemini surfactant in these reactions attain a value of ~103 and are determined mainly by substrate concentration in the micellar pseudophase.  相似文献   

15.
Russian Journal of Organic Chemistry - Completely substituted p-nitrosophenols were synthesized by cyclocondensation of dimethyl 3-oxopentanedioate with 2-(hydroxyimino)-1-pyridylbutane-1,3-diones....  相似文献   

16.
New A-ring or/and C-ring modified methyl oleanolate derivatives were prepared. New simple method of synthesis of 3,12-diketone (3) from methyl oleanonate (2) was worked out. The obtained new compounds were tested for cytotoxic activity on KB, MCF-7 and HeLa cell lines. The derivatives had acetoxy, oxo or hydroxyimino function at the C-3 position and in some cases oxo, hydroxyimino or acyloxyimino group at the C-12 position. Almost all of the compounds showed strong cytotoxic activity, higher than unchanged oleanolic acid. The most active substances turned out to be the derivatives with acyloxyimino function, especially 4 and 8d.  相似文献   

17.
The title compound, (2,6‐diacetylpyridine bis{[2‐(hydroxyimino)propanoyl]hydrazone}(2−))nickel(II) dimethyl sulfoxide solvate monohydrate, [Ni(C15H17N7O4)]·C2H6OS·H2O, represents the first example of square‐planar N4 coordination via N atoms with four different functions, namely amide, azomethine, hydroxyimino and pyridine. The coordination polyhedron of the central Ni atom has a slightly distorted square‐planar geometry. The 2,6‐diacetylpyridine bis{[2‐(hydroxyimino)propanoyl]hydrazone} ligand forms one six‐ and two five‐membered chelate rings, and a pseudo‐chelate ring through an intramolecular hydrogen bond with an amide group as donor and a deprotonated hydroxyimino group as acceptor, resulting in a pseudomacrocyclic arrangement.  相似文献   

18.
A new and unequivocal synthesis of pteroyl-γ-L-glutamyl-γ-L-glutamyl-L-glutamic acid free of isomers is described. A melt of N(2′)-acetyl-6-formylpterine and tetramethyl-N-(p-amino-benzoyl)-γ-L-glutamyl-γ-L-glutamyl-L-glutamatewas quantitatively converted to the corresponding azomethin IX. NaBH4-reduction followed by basic hydrolysis of acetyl and methylester groups gives pure pteroyl-γ-L-glutamyl-γ-L-glutamyl-L-glutamic acid in good yield.  相似文献   

19.
A sequential kinetic resolution catalyzed by halohydrin dehalogenase was employed for the synthesis of two valuable enantiopure building blocks. Resolution of methyl 4-chloro-3-hydroxybutanoate methylester ((R,S)-2) with use of a Trp249Phe mutant of halohydrin dehalogenase yielded methyl 4-cyano-3-hydroxybutanoate methylester ((S)-4) with 96.8% ee (40% yield) and (S)-2 with 95.2% ee (41% yield). This reaction is carried out in aqueous solution under mild conditions and provides access to a useful statin side-chain building block.  相似文献   

20.
The oximation of 2-(R1-amino)-4-(R2-imino)naphthalen-1(4H)-ones with hydroxylamine hydrochloride in pyridine afforded 2-(R-amino)-4-(hydroxyimino)naphthalen-1(4H)-ones.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号