Synthesis,Structure, and Biological Activity of Products of Reactions of 3,4-Dioxohexane-1,6-dioic Acid Esters with 2-Aminophenol

Bioactive derivatives of 1,4-benzoxazine have been prepared via reactions of 3,4-dioxohexane-1,6- dioic (ketipic) acid esters with 2-aminophenol. (2'Z)-2,2'-(2-Hydroxy-2H-1,4-benzoxazin-2-yl-3-ilidene)diacetic acid esters or (2Z)-[2-oxo-2H-1,4-benzoxazin-3(4H)-ylidene]acetic acid esters can be formed depending on the conditions. The structures of the products of dialkyl ketipate esters reactions with 2-aminophenol were determined by means of X-ray diffraction. It has been demonstrated that the prepared compounds exhibit antimycotic activity against test cultures of plant pathogenic fungi (Fusauium sp., Alternarium sp., and Bipolaris soraciniana).     

Reactivity of Organolithium Reagents to 2,3,4,5-Tetraphenylcyclopentadienone and Crystal Structures of Addition Products

The conjugate addition reactions of four organolithium reagents to 2,3,4,5-tetraphenylcyclopentadienone (tetracyclone) were investigated to reveal the reactivity of organolithium reagents to tetracyclone. The results show that 1,2-addition products 2,3,4,5-tetraphenyl-1-(2-thienyl)-2,4-cyclopentadien-1-ol(1), 1-n-butyl-2,3,4,5-tetraphenyl-2,4-cyclopentadien-1-ol(2) and 1,2,3,4,5-pentaphenyl-2,4-cyclopentadien-1-ol(3) were synthesized in excellent yields while tetracyclone reacted with 2-thienyllithium, n-butyllithium and phenyllithium, respectively. Interestingly, three 1,2-, 1,4- and 1,6-addition isomers 1-tert-butyl-2,3,4,5-tetraphenyl-2,4-cyclopentadien-1-ol(4), 4-tert-butyl-2,3,4,5-tetraphenyl-2-cyclopenten-l-one(5) and 2-tert-butyl-2,3,4,5-tetraphenyl-3-cyclopenten-l-one(6), were simultaneously obtained by the conjugate addition reaction of tert-butyllithium with larger steric hindrance to tetracyclone. Compounds 1-6 were characterized by ¹H and ¹³C NMR spectra, Fourier transform infrared(FTIR) spectra and mass spectra(MS). The crystal and molecular structures of compounds 1, 2 and isomers 5, 6 were determined by X-ray single crystal diffraction technique. The results imply that the steric hindrance of tert-butyllithium probably play a key role in controlling the conjugate addition reaction. The conjugate addition mechanism of organolithium reagents to tetracyclone was proposed.     

Addition of Organosamarium Reagents toα, β-Unsaturated Esters

Compared to the extensive use of samarium diiodide in organic synthesis', little reportsappeared on the application of samarium metal in organic synthesis. As early as 1971Evans and co-workers had prepared phenylsamarium iodide from iodo-benzene andsamarium metal'. But they found that samarium is not so active as ytterbium. In 1986Fukuzawa also prepared the organosamarium intermediate similar to Grignard reagent'.It was Curran who firstly proved and named the samarium Grignard reaction in 19…     

Solubility and Mixing Thermodynamic Properties of Capecitabine in Five Acetic Acid Esters at Various Temperatures

Russian Journal of Physical Chemistry A - In pharmaceutical industry, capecitabine is often purified by crystallization from acetic esters. In this work, by using laser dynamic isothermal method,...     

Addition Reactions of Glycal Esters: Access to Glycosyl Donors of Kdo,d-glycero-d-talo- and d-glycero-d-galacto-2-Octulosonic Acid Residues

ABSTRACT

Addition reactions of O-acetylated glycal esters of Kdo mono-, α-(2→8)- and α-(2→4)- linked Kdo disaccharide derivatives 1a - c with NIS in acetic acid afforded good yields of trans-diaxial as well as minor amounts of trans-diequatorial and cis-configured 2-O-acetyl-3-deoxy-3-iodo derivatives, which were efficiently reduced with Bu₃SnH/AIBN to give the corresponding per-O-acetylated Kdo methyl ester derivatives. Similar reactions of 1a with NBS or NCS furnished the trans-diaxial 2-O-acetyl-3-bromo-3-deoxy- as well as 3-chloro-3-deoxy derivatives as the main products. Reaction of 1a with NBS in aqueous MeCN provided the 2,3-trans-bromohydrin derivative 11c, which upon treatment with DBU in MeCN gave the elimination product 11 and the α-2,3-anhydro derivative 12 as a suitable donor of glycosides with D-glycero-D-talo- or D-glycero-D-galacto configuration, respectively.     

Addition of carbon-centered radicals to C60. Determination of the rate constants by the spin trap method

The rate constants of addition of the^.CMe₃,^.CH₂Me,^.CH₂(CH₂)₃Me,^.CH₂Ph,^.CH₂CH=CH₂, and^.CH(Me)Et radicals to fullerene C₆₀ were determined by the method of competitive addition of free radicals to spin traps. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp 2369–2372, December, 1999.     

Synthesis of Some New 3-Substituted Benzofuran Derivatives by Cyclization of Various Phenoxy Acetic Acid Ethyl Esters

Six new 2-[3-(1-benzofuran-3-yl)-1H-pyrazol-1-yl] pyridines were synthesized by cyclization of various phenoxy acetic acid ethyl esters using NaOEt in ethanol at room temperature.     

Derivatives of Some 2-Chloroethylphosphonic Acid Esters,with Plant Growth Regulating Activity

Abstract

A method for the synthesis of esters of 2-(dimethylsulfonium)ethylphos-phonic acid and the results of some trials showing the plant growth regulating activity of these compounds are presented. For the synthesis of the mentioned compounds, dimethyl sulphide is reacted with 2-chloroethylphosphonic acid esters; these esters are obtained through the complex[1] of AlCl₃, PCl₃ and 1,2-dichloroethan (1). Using the optimum reaction conditions, very good yields were obtained (96–99%). This complex is reacted with different alcohols to give 2-chloroethylphosphonic acid esters (2) (R?Me, Et, Pr, i-Pr, Bu, i-Bu, Pe). Using the optimum reaction conditions, in the case of methanol the maximum obtained yield was 50%. In the case of the other alcohols, the obtained yields were between 76 and 83%. An exception is i-propanol. whose ester was obtained with low yields and the reaction parameters modification have little influence on the yield. The reaction of the esters with dimethyl sulphide gives, in good yields (between 69 and 79%). esters of 2-(dimethylsulfonium)ethylphosphonic acid (3). substances with plant growth regulating activity.     

羧酸酯水解与氨解反应的胶团催化研究

较系统地研究了在有氨和无氨缓冲体系中ｐＨ变化对羧酸酯脱酰反应速度和胶团催化作用的影响，提供在两种缓冲体系中反应速度随溶液ｐＨ变化的规律，结果表明ＣＴＡＢ胶团对对硝基苯酚丙酸酯和乙酸酯水解反应的催化效率随溶液ｐＨ上升而削弱，参硝基苯酚丙酸酯和乙酸酸在含氨的缓冲体系中有水解和氨解反应同时进行，ＣＴＡＢ胶团对水解反应正催化作用，而对氨解反应则显示负催化作用，这使得ＮＨ３－ＮＨ４Ｂｒ缓冲体系中ＣＴＡＢ胶团     

C,H coupling constants of propene

The proton coupled ¹³C NMR spectrum of propene has been analysed at 100.6 and 25.2 MHz and a complete set of C,H coupling constants is reported. In particular, vicinal and one-bond coupling constants are discussed with respect to substituent effects of alkyl groups. An incremental method allows us to predict ¹J(CH) in more highly methyl-substituted alkenes.     

Lewis Acid Mediated Addition of Tri-n-Butylstannylmethylisoxazole with Aldehydes

Lewis acid mediated addition of 5-(tri-n-butylstannyl)methyl-3-methylisoxazole and its analogues with aldehydes have been carried out. Corresponding 5-(β-hydroxy)ethylisoxazoles were obtained in moderate yields, without ring opening of the isoxazole.     

Highly Selective Process for Epoxidation of Fatty Acid Methyl Esters with Peroxyacetic Acid

Specific features of the double-stage process in which unsaturated compounds and, in particular, fatty acid methyl esters of vegetable oils are epoxidated with peroxyacetic acid obtained ex situ in aqueous solutions of acetic acid and hydrogen peroxide under catalysis with Amberlyst 15 Dry ion-exchange resin were examined. It was shown that the independently occurring processes in which the peroxy acid is heterogeneously catalytically formed and epoxy compounds are synthesized can substantially raise the formation selectivity of epoxides with respect to double bonds in fatty acid methyl esters and simplify the simulation of these processes and their technological implementation.     

Acyl Iodides in Organic Synthesis: V. Reactions with Carboxylic Acid Esters

Acyl iodides react with alkyl, alkenyl, and aralkyl esters derived from saturated, unsaturated, and aromatic mono- and dicarboxylic acids in the absence of a catalyst. The reaction involves cleavage of the OR bond and formation of organic iodide RI (including CH₂=CHI) and one or two symmetric carboxylic acid anhydrides. Phenyl acetate reacts with benzoyl iodide to give acetyl iodide and phenyl benzoate as a result of cleavage of the (O=)C–O bond. The reaction of diethyl fumarate with acetyl iodide is accompanied by cis– trans isomerization to afford maleic anhydride. In the reactions of acetyl iodide with diethyl oxalate and diethyl malonate, CO and CO₂ and CO₂ and polyketene are formed, respectively, in addition to ethyl iodide and acetic anhydride. Ethyl esters of strong organic acids, e.g., ethyl trihaloacetates, failed to react with acyl iodides under analogous conditions.     

13C,13C coupling constants of conjugated dienes

One bond ¹³C,¹³C- and ¹³C,¹H-coupling constants have been measured for some 1,2-dimethylene-cycloalkanes, as well as for 2,3-dimethylbuta-1,3-diene and methylenecyclobutane. The results for 2,3-dimethylbuta-1,3-diene confirm the findings for buta-1,3-diene, i.e. that J(C-1, C-2) is smaller for the diene than for the correspondingly substituted monoene. No differences have been found between the ¹J(CC) exocyclic coupling constants of the dimethylene and monomethylene cycloalkanes.     

Reaction of Amino Acid Esters and Amides with o-Phthalaldehyde. Limitations in Fluorescent Yield

Abstract

Amino acid esters and amides fail to produce strong fluorescence following their reaction with o-phthalaldehyde (OPA) in the presence of β-mercaptoethanol. The lack of luminescence appears to arise from a quenching phenomenon rather than from reduced reactivity of these substrates toward OPA. The amido hydrogen in the peptide linkage has been implicated in the loss in fluorescence yield.

o-Phthalaldehyde (OPA) has proven to be a very useful reagent for converting amino acids to fluorescent isoindole derivatives¹. This derivatization process permits the visualization of femtomolar quantities of amino acids. Unfortunately, this technique has not been applied successfully to the derivatization of peptides^2,3, except for those containing lysine residues, in which the terminal amino group is attacked by the reagent⁴. It is the purpose of this note to more clearly define the limitations of OPA as a fluorogenic reagents for peptides and amino acid esters.     

Complexes of Lanthanide Nitrates with Alkyl Esters of Bromomethylenediphosphonic Acid

Complexes of lanthanide nitrates (La, Ce, Sm, Gd, Er, and Yb) with tetraethyl and tetraisopropyl esters of bromomethylenediphosphonic acid were prepared. The complexes were characterized by elemental analysis, IR spectroscopy, and, in some cases, NMR. The data confirm that diphosphonates coordinate with two P[dbnd]O groups, and there are no indications for the existence of noncoordinated P[dbnd]O groups. The structure of the complexes depends only on the ionic radius of the central metal atom and not on changes in the electronic or steric behavior of the ester groups. For the complexes of La, Ce, Sm, and Gd nitrates, the formula is LnL₂(NO₃)₃, and for Er and Yb nitrates it is Ln₂L₃(NO₃)₆ (Ln[dbnd]La, Ce, Sm, Gd, Er, Yb; L = diphosphonate).     

Molecular Recognition of Chiral Zinc Porphyrin with Amino Acid Esters

One kind of novel chiral porphyrin and its zinc complex were synthesized and characterized. The molecular recognition of chiral zinc porphyrin towards amino acid esters in CHCl₃ was investigated by UV‐vis spectral titration method. The associative constants of the molecular recognition reactions were all K_D>K_L and followed the order of K(PheOMe)>K(LeuOMe)>K(ValOMe)>K(AlaOMe) in host (Zn(L‐BocTyr)TAPP). Circular dichroism spectra were used to explain chiral molecular recognition. The minimal energy conformation of host‐guest molecular system was sought by molecular dynamics method. The molecular recognition process of this host‐guest system was calculated by quantum chemistry and the results were explained by the experiments     

Transition Metal-Free N-Arylation of Amino Acid Esters with Diaryliodonium Salts

A transition metal-free approach for the N-arylation of amino acid derivatives has been developed. Key to this method is the use of unsymmetric diaryliodonium salts with anisyl ligands, which proved important to obtain high chemoselectivity and yields. The scope includes the transfer of both electron deficient, electron rich and sterically hindered aryl groups with a variety of different functional groups. Furthermore, a cyclic diaryliodonium salt was successfully employed in the arylation. The N-arylated products were obtained with retained enantiomeric excess.