Research on the aromas. On the aroma of coffee. I

The analysis of a coffee concentrate is described: 202 constituents have been identified, 154 of which for the first time. Some of these compounds are new chemicals; their synthesis is described. Most identifications are based upon mass spectrometry combined in many cases with IR. spectrometry and comparison with reference compounds. MS. and IR. data are given in detail. The analysis shows that a large number of minor constituents is present, many of which could not be identified.     

Analytical techniques for the investigation of coffee aroma

A review is provided on instrumental measurement techniques used in coffee aroma analysis comprising sample preparation and identification techniques. In addition, a brief survey of the complex nature of coffee aroma is given.     

Reaction of alkylhydrazines. II. vic-disubstituted pyridines and pyridopyridazines

A series of 2,3-disubstituted pyridines and pyrido[2,3-d]pyridazines have been synthesized. The molecular structure of the compounds have been elucidated by using chromatography; ir, nmr, and mass spectrometry; and chemical methods, in particular metal complexation. The new compounds offer interesting chemistry and are envisaged to function as potential chemotherapeutic and pharmacodynamic agents.     

Rapid synthesis of kahweofuran and its derivatives, the coffee aroma components

Kahweofuran, as an impact flavor component of roasted coffee and possesses the 6-methyl-2,3-dihydrothieno[2,3-c]furan structure, was rapidly synthesized from 2-acetyl-3-hydroxymethylthiophene by the formal reductive cyclization using the Wilkinson’s catalyst. Similarly, the syntheses of the 4-methyl, 6-ethyl and 4,6-dimethyl derivatives were also achieved in favorable yields.     

New photocleavable structures. II. α-Cleavable photoinitiators based on pyridines

A series of novel pyridine-based type I photoinitiators were synthesized. UV spectroscopy revealed absorption characteristics very similar to those of a commercially available hydroxyalkylphenone [2-hydroxy-2-methyl-1-phenyl propan-1-one ( 1b )]. Photo-differential scanning calorimetry was used to study the polymerization kinetics of lauryl acrylate photoinitiated by the new pyridines. Under a nitrogen atmosphere, a 3-substituted derivative [2-hydroxy-2-methyl-1-pyridin-3-yl-propan-1-one ( 3b )] gave results comparable to those obtained with 1b . Measurements under air indicated decreased sensitivity toward oxygen quenching reactions. Additionally, pyridine derivatives showed good water solubility (4.9 g/100 mL). Preliminary steady-state photolysis experiments with 2,2,6,6-tetramethyl-1-piperidinyloxy as a radical scavenger were carried out, and the α-cleavage mechanism was found to be the main reaction pathway. The quantum yields of α-cleavage were approximately 0.30 ± 0.04 for 3b and 0.18 ± 0.03 for 1b . © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 752–764, 2004     

A versatile new synthesis of quinolines and related fused pyridines. Part II.

The conversion of acetanilides to 2-chloroquinoline-3-aldehydes by Vilsmeier reagent proceeds efficiently in POCl₃ solution at 75°. The intermediate, in which the acetyl group has been diformylated, may in some cases be isolated and separately cyclised.     

Use of computerized pattern recognition in the analysis of stress induced changes in coffee aroma

The aim of the study was to evaluate changes in the aroma of coffee that has been exposed to heat for some time. Coffee grinds were extracted with water. The coffee was kept hot and sampled periodically using a continuous gas phase extraction method. Gas chromatography/mass spectrometry was used to follow changes in chromatographic profiles. Data were subjected to pattern recognition. About 20 substances were found that significantly changed when exposed to heat.     

Developing qualitative extraction profiles of coffee aromas utilizing polymeric ionic liquid sorbent coatings in headspace solid-phase microextraction gas chromatography-mass spectrometry

Two solid-phase microextraction (SPME) sorbent coatings based on polymeric ionic liquids (PILs) have been utilized for the analysis of complex coffee aroma samples. The PIL-based SPME coatings examined, namely, poly(1-(4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide) [poly(VBHDIm⁺ NTf₂⁻)], with ∼14-μm thickness, and poly(1-vinyl-3-hexylimidazolium chloride) [poly(ViHIm⁺ Cl⁻)], with ∼8-μm thickness, were employed for the headspace determination of up to 49 analytes from four different coffee beans: two French roast coffees of different brands, Sumatra coffee, and decaffeinated Sumatra coffee. The analysis was conducted using gas chromatography coupled to mass spectrometry. For comparative purposes, the commercial polyacrylate (PA, 85-μm film thickness) SPME coating was utilized under the same extraction conditions. The three SPME coatings tested behaved quite differently as a function of the families of compounds extracted. Thus, the poly(VBHDIm⁺ NTf₂⁻) coating was extremely selective for aldehydes while also exhibiting good extraction efficiencies for acids. The poly-(ViHIm⁺ Cl⁻) coating exhibited superior performance for aromatic alcohols, and the PA coating worked better for heterocyclic aromatics. Both PIL-based SPME sorbent coatings demonstrated exceptional selectivity and extraction efficiency when dealing with complex coffee aromas in spite of their small film thicknesses.     

Synthesis of heterocyclic compounds. II. A simple one-step synthesis of pyridines from aldehydes and malononitrile

The condensation of several aldehydes with malononitrile in the presence of a alcohol-alkoxide system provides a new simple, one-step route to 4-substituted 2-amino-3,5-dieyano-6-alkoxy-pyridines. The best results are obtained with the aromatic aldehydes. The structure of these compounds was established from a study of their infrared, ultraviolet and nuclear magnetic resonance spectra.     

The Separation of Volatile N-Nitrosamines and Pyrazines

Abstract

Peaks on a gas chromatogram due to pyrazines and N-nitrosamines may be differentiated by selective adsorption of the pyrazines on a precolumn containing cuprous thiocyanate.     

吡嗪类化合物的合成及其抗血小板凝集活性测试

为提高川芎嗪的抗血小板凝集活性,分别以不同的二胺、2,3-丁二酮和硫辛酸为起始原料,采用溴代、水解、环化、氧化、氢化、取代等反应,通过四条路线合成了7个川芎嗪衍生物,其结构经1H NMR、13C NMR及ESI-MS确证。采用Born比浊法初步测试了化合物的体外抗血小板凝集活性,结果显示,化合物1(IC50=0. 26mmol/L)、2(IC50=0. 27mmol/L)和7(IC50=0. 21mmol/L)对由二磷酸腺苷(ADP)诱导的血小板凝集具有一定的抑制活性,优于先导化合物川芎嗪(IC50=0. 49mmol/L)。因此,在不改变川芎嗪药效团的前提下对其进行不同程度的环化,能明显提高川芎嗪的抗血小板凝集活性,此研究为后期化合物的结构修饰提供了一定的参考价值。     

Preparation and characterization of tetrahalodimolybdenum(II) complexes with alkyl-substituted pyridines

The preparation and characterization of new tetrahalodimolybdenum(II) complexes with alkyl-substituted pyridines is described. IR and visible data are used to infer structural information with respect to previously prepared complexes of this type.     

Syntheses and Applications of 1,2,3-Triazole-Fused Pyrazines and Pyridazines

Pyrazines and pyridazines fused to 1,2,3-triazoles comprise a set of heterocycles obtained through a variety of synthetic routes. Two typical modes of constructing these heterocyclic ring systems are cyclizing a heterocyclic diamine with a nitrite or reacting hydrazine hydrate with dicarbonyl 1,2,3-triazoles. Several unique methods are known, particularly for the synthesis of 1,2,3-triazolo[1,5-a]pyrazines and their benzo-fused quinoxaline and quinoxalinone-containing analogs. Recent applications detail the use of these heterocycles in medicinal chemistry (c-Met inhibition or GABA_A modulating activity) as fluorescent probes and as structural units of polymers.     

Azulene‐substituted pyridines and pyridinium salts. Synthesis and structure. 1. Azulene‐substituted pyridines

4‐Azulen‐1‐yl substituted 2,6‐dimethyl‐and 2,6‐diphenyl‐pyridines are obtained in good yields from the reaction of corresponding 4‐azulen‐1‐yl‐pyranylium salts and ammonium acetate in ethanol or starting from 4‐chloro‐2,6‐diphenyl‐pyranylium salts in two steps: reaction with azulenes followed by in situ treatment with ammonium acetate. The effect of substitution at the 3‐position of the heterocycle was taken into account. The structure assignment was accomplished with NMR and uv‐vis spectra.     

Aromatic annelation. I. Synthesis of pyridines.

The preparation of substituted pyridines from cycloalkanones by elaboration of an aromatic ring is described.