Sample records for heterocyclic compounds
from WorldWideScience.org

Sample records 1 - 10 shown.



1

Componentes voláteis do café torrado. Parte I: compostos heterocíclicos/ Volatile components in roasted coffee. Part I: heterocyclic compounds

De Maria, Carlos Alberto Bastos; Moreira, Ricardo Felipe Alves; Trugo, Luiz Carlos
1999-04-01

Resumo em inglês A review of heterocyclic compounds in roasted coffee is presented. The contents, precursors and sensorial properties of furans, pyrroles, oxazoles, thiazoles, thiophenes, pyrazines and pyridines are discussed. The impact heterocyclic compounds of coffee aroma are described.

Scientific Electronic Library Online (Portuguese)

2

Métodos de obtenção e aplicações sintéticas de tiazóis, uma importante classe de compostos heterocíclicos/ Methodologies for the preparation and synthetic application of thiazoles, an important class of heterocyclic compounds

Souza, Marcus Vinícius Nora de; Ferreira, Sabrina B.; Mendonça, Jorge Souza; Costa, Marília; Rebello, Fabiane Ramos
2005-02-01

Resumo em inglês Thiazoles comprise an important class of heterocyclic compounds present in many potent biologically active molecules. This heterocyclic ring also shows various applications in organic synthesis to obtain new compounds. This paper presents different methodologies for the preparation of thiazole ring systems, as well as their synthetic applications.

Scientific Electronic Library Online (Portuguese)

3

Principais métodos de síntese de amidinas/ Synthetic approaches to amidines

Santos, Maurício Silva dos; Bernardino, Alice Maria Rolim; Souza, Marcos Costa de
2006-12-01

Resumo em inglês The amidine functional group is found in a wide range of natural products and is biologically active against several pathogens. In addition, amidines have long been regarded as useful intermediates in the synthesis of heterocyclic compounds. Consequently, a great number of methods have been developed for the preparation of amidines. Pinner's method is the most commonly used. Conventional methods include: - the addition of metal amides or amines to nitriles, the addition o (mais) f amines to imido esters and the condensation of amides with amines in the presence of halogenating reagents. In this report, the main methods for synthesis of amidines will be described.

Scientific Electronic Library Online (Portuguese)

4

Novos derivados do sistema heterocíclico 1H-pirazolo[3,4-b]piridina: síntese e assinalamentos de hidrogênios e carbonos por RMN 1D e 2D/ New derivatives of 1H-pyrazolo[3,4-b]pyridine heterocyclic system: synthesis and hydrogen and carbon assignments by 1D and 2D NMR

Mello, Heloisa de; Silva, Edson Fernandes da; Echevarria, Aurea; Carvalho, Mário Geraldo de; Bernardino, Alice Maria Rolim
1999-02-01

Resumo em inglês The synthesis and NMR analysis of seven new 4-(aryl)amino-5-carboethoxy-1,3-dimethyl-1H-pyrazolo[3,4- b]pyridines (7-13) are described. The synthetic approach used involved the preparation of intermediates 5-aminopyrazol (4), the enamine derivative (5) and the 4-chloro-1H-pyrazolo[3,4-b]pyridine (6). Compounds (7-13) were obtained by treatment of 6 with the desired aniline. The structures of new heterocyclic compounds and their precursors intermediates were assigned on th (mais) e basis of spectral analysis including 1D and 2D NMR experiments [¹H; 13C{¹H} and DEPT; ¹H x ¹H - COSY; ¹H x13C - COSY, nJ CH, n = 1, 2 or 3 (HETECOR and COLOC)].

Scientific Electronic Library Online (Portuguese)

5

Métodos sintéticos para preparação de 2,2'-bipiridinas substituídas/ Synthetic methods for preparation of substituted 2,2'-bipyridines

Donnici, Claudio Luis; Oliveira, Ione Maria Ferreira de; Temba, Eliane Sílvia Codo; Castro, Maurício Costa Rogério de
2002-07-01

Resumo em inglês The 2,2'-bipyridine has been entitled as the most widely used ligand. Nowadays there is a large variety of known molecules comprising at least two 2,2'-bipyridine units and the number of applications in many areas such as catalysis, new materials, optoeletronics and electrochemistry have increased very much in the past decades. Nevertheless, there is no article that gives an overview of the main synthetic methods for obtaining the substituted 2,2'-bipyridines, generally n (mais) on available. This article presents a synthetic discussion about the three different methods (coupling reaction, ciclo-functionalization and functionalization of the heteroaromatic rings of 2,2'-bipyridine) for preparing these heterocyclic compounds and also provides a practical and fundamental guide, for obtaining more than eighty different symmetric and unsymmetrical substituted 2,2'-bipyridines, shown in a table with the corresponding references.

Scientific Electronic Library Online (Portuguese)

6

Heterociclos 1,2,3-triazólicos: histórico, métodos de preparação, aplicações e atividades farmacológicas/ 1,2,3-triazolic heterocycles: history, preparations, applications and pharmacological activities

Melo, Júlio O. F.; Donnici, Claudio Luis; Augusti, Rodinei; Ferreira, Vitor F.; Souza, Maria Cecília B. V. de; Ferreira, Maria Lourdes G.; Cunha, Anna C.
2006-06-01

Resumo em inglês The 1,2,3-triazole, known since the end of 19th century, is a very widely used heterocyclic system present in many synthetic substances and commercial pharmaceutical compounds. In fact, 1,2,3-triazoles show several applications in many areas especially as medicines against many diseases like cancer, AIDS, Parkinson and Alzheimer. Nowadays there is a large variety of known methods to obtain these heterocyclic compounds comprising mainly three synthetic routes. Nevertheless (mais) , there is no article that gives an objective overview of the synthetic methods for obtaining these kinds of azoheterocycles. This paper presents a brief history of this class of compounds, and a synthetic discussion concerning the main synthetic methods for its preparation, such as cyclization through hydrazones, concerted cycloadditon [2+3] and pseudopericyclic cyclization - and some others of restricted application, but also important. Finally, this paper also provides a brief overview on pharmacological applications of some 1,2,3-triazoles.

Scientific Electronic Library Online (Portuguese)

7

Formação de toxinas durante o processamento de alimentos e as possíveis conseqüências para o organismo humano/ Toxin formation during food processing and possible consequences to the human body

Marques, Anne y Castro; Valente, Tessa Bitencourt; Rosa, Cláudia Severo da
2009-04-01

Resumo em português A produção de alimentos envolve inúmeras reações químicas, durante as quais podem ser geradas substâncias tóxicas ao organismo humano. A produção destas substâncias pode ocorrer de diferentes maneiras, variando em quantidade e em grau de toxicidade. Este trabalho objetivou estudar a produção de toxinas no processamento de alimentos, assim como as conseqüências da ingestão dessas substâncias para o ser humano. O estudo foi realizado a partir de extensa pes (mais) quisa bibliográfica. As principais reações na formação de compostos tóxicos apresentadas no decorrer do estudo são: degradação de lipídios, hidrogenação, pirólise e defumação. Entre as substâncias formadas, destacam-se: peróxidos, ácidos graxos trans, aminas heterocíclicas e hidrocarbonetos aromáticos policíclicos. O profissional nutricionista necessita conhecer como ocorre a formação de toxinas durante os variados processamentos que envolvem alimentos, assim como os riscos para a saúde de quem consome essas substâncias. Também é preciso propor técnicas de processamento adequadas, visando ao bem-estar do consumidor e à manutenção das propriedades nutricionais do alimento. Resumo em inglês Food production involves innumerable chemical reactions that may generate substances that are toxic to the human body. These substances can be produced in different ways, in varying amounts and degree of toxicity. The objective of this study was to investigate the production of toxins during food processing, as well as theconsequences of their ingestion. This study was based on extensive literature research. The main reactions leading to toxic compounds are: lipid degrada (mais) tion, hydrogenation, pyrolysis and smoking. Some of the formed substances are: peroxides, trans fatty acids, heterocyclic amines and polycyclic aromatic hydrocarbons. Dietitians need to know how toxins form during the various foods processing methods, as well as their health risks for consumers. It is also necessary to propose processing techniques that ensure the consumer's wellbeing and retain the nutritional properties of the food.

Scientific Electronic Library Online (Portuguese)

8

Espectro infravermelho e análise conformacional do composto 3-fenil-2-oxo-1,2,3-oxatiazolidina/ A semiempirical infra-red spectrum of the 3-phenyl - 1,2,3 - oxathiazolidine 2-oxide

Santos, Hélio F. dos; Almeida, Wagner B. de; Val, Amélia M. G. do; Guimarães, Afonso C.
1999-09-01

Resumo em inglês The infrared (IR) spectra of the four distict conformers located on the multidimensional potential energy surface (PES) for the 3-phenyl-1,2,3-oxathiazolidine 2-oxide compound have been calculated using the semiempirical quantum-mechanical method PM3. The band spectra are reported and compared directly with the experimental spectrum. The IR intensities are shown to be much more sensitive to conformational changes than the vibrational frequencies and so, the theoretical an (mais) alysis of the IR spectrum can be used as a tool for helping in the elucidation of the structure of heterocyclic compounds.

Scientific Electronic Library Online (Portuguese)

9

Contribuições recentes da reação de hidroformilação na síntese de produtos farmacêuticos: parte II/ Current improvement to the synthesis of pharmaceuticals by hydrofor-mylation reaction: part II

Botteghi, Carlo; Marchetti, Mauro; Del Ponte, Gino
1997-02-01

Resumo em inglês The hydroformylation reaction represents one of the most important C1-chemistry area in the chemical industry. This catalytic process, which has been developed up to now mainly to the production of commodities chemicals, has shown a remarkable potential for the preparation of several categories of specialty chemicals and in particular pharmaceutical compounds. Arylpropanoic acids, various amines containing aryl groups, and intermediates for the preparation of vitamins, ca (mais) rbocyclic and heterocyclic compounds and many other classes of organic molecules endowed with pharmacological activity are currently accessible in good-to-high yields through hydroformylation of selected olefinic substrates. The asymmetric hydroformylation is going to reach the stage of maturity and hence to contribute in solving many troublesome synthetic problems connected with the preparation of pharmacologically active compounds with very high enantiomeric purity. The present survey emphasizes the usefulness of synthesis gas as a starting material in fine chemistry, which is expected to be important for industry.

Scientific Electronic Library Online (Portuguese)

10

Componentes voláteis do café torrado. Parte II. Compostos alifáticos, alicíclicos e aromáticos/ Volatile components in roasted coffee. Part II. Aliphatic, alicyclic and aromatic compounds

Moreira, Ricardo Felipe Alves; Trugo, Luiz Carlos; De Maria, Carlos Alberto Bastos
2000-04-01

Resumo em inglês This review is about the aliphatic, alicyclic and aromatic compounds (non-heterocyclic compounds) that are present in the volatile fractions of roasted coffees. Herein, the contents, aroma precursors and the sensorial properties of volatile phenols, aldehydes, ketones, alcohols, ethers, hydrocarbons, carboxylic acids, anhydrides, esters, lactones, amines and sulphur compounds are discussed. Special attention is given to the compounds of these groups that are actually important to the final aroma of roasted coffees.

Scientific Electronic Library Online (Portuguese)