Synthesis of triterpenoid sulfates using the SO3—dimethyl sulfoxide complex

The 3-sulfates of oleanolic, echinocystic, and betulinic acids have been synthesized with the use of the SO₃—dimethyl sulfoxide sulfating complex.Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 91–93, January–February, 1999.     

Synthesis of 2-functionally substituted oxazolines and oxazolidines from methyl bromopropiolate and Β-amino alcohols

The reaction of methyl bromopropiolate with -amino alcohols containing a primary amino group generally results in the formation of 2-(methoxycarbonylmethyl)-²-1,3-oxazolines, while in the reaction with N-methyl- and N,N-dimethyl-substituted -aminoalcohols, 2-(methoxycarbonylmethylene)-1,3-oxazolidines, or their salts are formed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 406–409, March, 1991.     

Synthesis and Crystal Structure of 6—Bromo—piperonal—dimethyl—acetal

1 INTRODUCTION 6-Bromo-piperonal-dimethyl-acetal is an intermediate used for the synthesis of natural products, such as podophyllotoxin[1] and the related compounds[2～6] due to the useful biological activities associated with some of its derivatives[7, 8]. In particular, glycoside derivatives of 4?dimethyl- 4-epipodophyllotoxin have been used in cancer chemotherapy[9, 10]. The title compound has been synthesized from raw material piperonal, after bromo substitution and acetal protection…     

Hydrolysis of fluoroalkyl-containing Β-aminovinyl ketones

The kinetics of hydrolysis of fluoroalkyl-containing -aminovinyl ketones R¹C(O)CHC(NHR³)R², in which the substituents CF₃ and HCF₂CF₂ are in the ketone (R¹) or enamine parts of the molecule (R²), was studied. In acid (pH < 5) and alkaline (pH > 10) media, they hydrolyze with the formation of the corresponding amines and -diketones. In an alkaline medium, the -diketones undergo cleavage to fluorinated acids and methyl ketones. The rate constants of hydrolysis in an acid medium change within a range of four orders, depending on the nature of the substituents. The presence of a fluoroalkyl group at the enamine reaction center increases the hydrolysis rate. In an alkaline medium, the rate constants vary within one order.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 664–669, March, 1991.     

Synthesis of substituted 2-phenyl-4-piperidinones from styryl Β-dimethylaminoethyl ketones and their steric structure

The difficultly obtainable substituted 2-phenyl-4-piperidinones were synthesized by the reaction of styryl -dimethylaminoethyl ketone hydrochlorides with aqueous solutions of ammonia or alkylamines. It was found using ¹H and ¹³C NMR spectroscopy methods that the cyclization process proceeds with the formation of pure stereoisomers of 4-piperidones with an equatorial disposition of all the substituents in the ring. The temperature for performing the cyclization is dependent on the number and position of the methyl substituents in the molecule of the starting substituted styryl -dimethylaminoethyl ketones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 224–227, February, 1991.     

Synthesis of methyl N-phenyl carbamate from dimethyl carbonate and 1,3-diphenyl urea under mild conditions

Synthesis of methyl N-phenyl carbamate from dimethyl carbonate and 1,3-diphenyl urea was investigated under atmospheric pressure. The results showed that homogenous catalyst sodium methoxide had the excellent activity to efficiently catalyze the synthesis of methyl N-phenyl carbamate under atmospheric pressure.     

Synthesis of a unique dimethyl thiazoline containing intermediate of novel peroxisome proliferator-activated receptors(PPAR)δ agonists

Peroxisome proliferator-activated receptor delta (PPARδ) is considered as a promising biological target for the development of new drugs to treat metabolic syndrome including hyperlipidemia. In this study, a simple and efficient method for the preparation of a unique dimethyl thiazoline containing intermediate (13) of new PPARδ agonists as GW501516 analogue is described. The intermediate 13 was readily obtained by coupling reaction of 4-(chloromethyl)-5,5-dimethyl-2-(4-(trifluoromethyl)phenyl)-4,5-dihydrothiazole (11) with 4-mercapto-2-methylphenol (12) in the presence of tetrabutylammonium hydrogensulfate (TBAHS) and Cs₂CO₃ in DMF at 80?°C for 1?h. This unique intermediate could be useful for the synthesis of various novel PPARδ agonists to understand the structural and biological significance of PPARδ.     

Binding energies of metal monocations to Β-lactones and Β-lactams. A theoretical study of cyclization effects

Ab initio calculations have been performed to study the association of-propiolactam and-propiolactone and their aliphatic analoguesN-methyl acetamide and methyl acetate with different metal monocations: Li⁺, Na⁺, Mg⁺, and Al⁺, in an effort to investigate cyclization effects on the gas-phase basicities of amides and esters, when the reference acid is not a proton. Similarly to what was found for protonation,N-methyl acetamide and-propiolactam are more basic than methyl acetate and-propiolactone, when the reference acids are the aforementioned metal monocations. However, cyclization effects on the corresponding binding energies for both kind of compounds do not parallel those observed for protonation energies, and-lactone is as basic as methyl acetate when the reference acid is Li⁺ and slightly more basic than methyl acetate when the attaching ion is Na⁺. This implies that when the interactions of the bases with the reference acids are essentially electrostatic the reactivity patterns change with respect to those observed when the interactions are essentially covalent.     

Synthesis of 5-ethoxymethylfurfural from saccharides using combined metal–surfactant catalyst in ethanol/dimethyl sulfoxide

Research on Chemical Intermediates - The synthesis of 5-ethoxymethylfurfural (EMF) from glucose using metal chlorides or combined metal–surfactant catalysts as Lewis acids in a solution of...     

Optically active cyclopropanols from the enzymatic resolution of dimethyl α-alkylsuccinates. Synthesis of chiral 2-vinylcyclobutanones and cyclohexenones.

(+)-(R) [or (-)-(S)] dimethyl α-methylsuccinates, obtained by the enantioselective hydrolysis of the racemic diester by porcine pancreatic lipase, undergo acyloin cyclization followed by stereoselective ring contraction to provide 1-alkenylcyclopropanols with high enantiomeric excesses.     

Effects of medium and chemical modification on thermal characteristics of Β-lactoglobulin

The thermal properties of -lactoglobulin (-LG) were studied by differential scanning calorimetry (DSC) under different medium conditions.pH, neutral salts, protein perturbants, and polyols all affected the DSC characteristics of -LG. Acylation with fatty acids also changed the thermal properties, particularly peak width at half-height. The results suggest that the structural stability of -LG is controlled by non-covalent forces, particularly electrostatic and hydrophobic interactions. Disulfide bonds did not contribute to the thermal response of -LG. Fatty N-acyl-amino acids caused marked increases in thermal stability and decreases in denaturation enthalpy, and additional peaks were observed in the presence of some palmitoyl derivatives.Contribution No. 2310, Centre for Food and Animal Research.We thank D. Raymond for her excellent technical assistance.     

Synthesis and characterization of porous WO3–SnO2 nanomaterials: An infrared study of adsorbed pyridine and dimethyl methylphosphonate

High surface area porous W/Sn oxide nanomaterials were prepared via water/oil based (W/O) emulsion. Tungstic acid solution was generated by cation exchange of sodium tungstate in acidic Dowex resin. The acid was then mixed with a clear homogeneous aqueous N-cetyl trimethyl ammonium bromide (CTAB) solution followed by a slow addition of 0.2 M SnCl₄ solution. The mixture was stirred for 24 h and then subjected to slow calcination at 500 °C. The prepared materials were characterized using SEM-EDX, BET surface area, and sorption of nitrogen and water. Fourier transform infrared spectroscopy (FTIR) was used to characterize the surface acidic properties using pyridine vapor as a probe. The materials were then tested toward the Dimethyl methylphosphonate (DMMP) adsorption at various temperatures using infrared spectroscopy. At elevated temperatures, the desorption of DMMP from WO₃ and SnO₂ surfaces results in forming methyl phosphonate that strongly bounds on the metal oxide surfaces. In contrast, the FTIR spectra showed that the adsorbed dimethyl methylphosphonate (DMMP) on the mixed W/Sn oxide powders can be molecularly desorbed without any decomposition.     

Sequential analysis of dimethyl sulfur compounds in seawater

A sequential method for the determination of dimethyl sulfur compounds, including dimethylsulfide （DMS）, dimethylsulfonio- propionate （DMSP） and dimethylsulfoxide （DMSO）, in seawater samples has been developed. Detection limit of 2.5 pmol of DMS in 25 mL sample, corresponding to 0.10 nmol/L, was achieved. Recoveries for dimethyl sulfur compounds were in the range of 68.6- 78.3%. The relative standard deviations （R.S.D.s） for DMS, DMSP and DMSO determination were 3.0, 5.4 and 7.4%, respectively.     

Synthesis of dimethyl 3-perfluoroalkyl-4-(3-oxo-2-triphenyl-phosphoranylidenbutanylidene)-pent-2-enedioate and its cyclization

The title compounds 5a-5c were prepared via the reaction of methyl 2-perfluoroal-kynoates (4) with methyl 5-oxo-4-(triphenylphosphoranylidene)hex-2-enoate (3), which was obtained from the reaction of methyl propynate (2) with acetylmethylenetriphenylphosphorane (1) at -5-0℃. Intramolecular elimination of Ph3PO took place when compound 5 was heated in aqueous methanol at 115-120℃ in sealed tube, yielding dimethyl 2-trifluoromethyl-4-methylisophthalate (6a) from 5a and methyl 5-acetyl-4-hydroxy-2-heptafluoropropanylbenzoate (6b) from 5b, respectively. The structures of compounds 5, 6a and 6b were confirmed by IR, MS, 1H NMR, 19F NMR and 13C NMR spectroscopy and elemental analyses. Rection mechanisms for the formation of compounds 5, 6a and 6b were proposed.     

Facile Synthesis of 2‐Alkylthio‐5,5‐dimethyl‐4H‐imidazol‐4‐ones

The isothiocyanate 3, obtained from aza‐Wittig reaction of iminophosphorane 2 with CS₂, reacts with phenylhydrazine to give thiosemicarbazide 4. Reactions of 4 with alkyl halides in the presence of K₂CO₃ directly provided 2‐alkylthio‐4H‐imidazol‐4‐ones 6 in good yields.     

Synthesis of nanocrystalline γ-Al_2O_3 by sol-gel and precipitation methods for methanol dehydration to dimethyl ether

The capability of sol-gel and conventional precipitation techniques for the synthesis of nanocrystalline γ-alumina was investigated. These catalysts were used for vapor-phase dehydration of methanol to dimethyl ether in a fixed-bed reactor under the same operating conditions (T = 300 ?C, P = 1 bar, LHSV = 2.8, 11.7, 26.1 h?1) and characterized by means of N2 adsorption-desorption, NH3-TPD, XRD, TGA and SEM techniques. According to the experimental results, the catalysts prepared using sol-gel method in non-aqueous medium showed better performance compared with those prepared by other methods.     

Synthesis and Crystal Structure of Tri-(2-mercaptopyridine N-oxide)bis(dimethyl sulfoxide) Dysprosium(III)

1 INTRODUCTION Transition-metal thiolato complexes have been of interest for the simulation of many metallo- enzymes where the thiolato group mimics the ligation of cysteinyl residues in proteins. Numerous complexes of transition elements with 1,2-bidentate oxothiolate ligands have been prepared[1~4]. Re- cently, we have studied a few transition metal complexes of 2-mercaptopyridine N-oxide (Hmpo) as bactericidal and antifungal reagents[5～7]. Although Hmpo exhibits unusual versatility…     

Improved Synthesis of Icaritin and Total Synthesis of β-Anhydroicaritin

Natural products icaritin and β-anhydroicaritin with P-glycoprotein(P-gp) inhibitory activities were ciently synthesized in nine steps from commercially available phloroglucinol. A modified Algar-Flynn-Oyamada cyclization and relay Claisen-Cope rearrangement were employed in this concise route. Oiir synthesis offers opportunities to synthesize various icariin analogues for biological and pharmacological investigations.