Molecules

97 KiB

Open AccessArticle

Preparation of New 2,3-Diphenylpropenoic Acid Esters – Good Yields Even for the More Hindered Z Isomers

by László Boros, Károly Felföldi and István Pálinkó

Molecules 2004, 9(4), 256-263; https://doi.org/10.3390/90400256 - 31 Mar 2004

Cited by 4 | Viewed by 8929

The potassium salt of E- and Z-2,3-diphenylpropenoic acids prepared in situ could be esterified efficiently in DMSO with the appropriate alkyl halides at room temperature. In this way 10 previously undescribed esters of these acids were synthesised and characterised. Excellent yields were observed [...] Read more.

The potassium salt of E- and Z-2,3-diphenylpropenoic acids prepared in situ could be esterified efficiently in DMSO with the appropriate alkyl halides at room temperature. In this way 10 previously undescribed esters of these acids were synthesised and characterised. Excellent yields were observed for most of the E isomers and the more hindered Z esters were also obtained in good yields, far better than those obtained applying the classical acid-catalysed esterification reaction. Full article

201 KiB

Open AccessArticle

Reactions of Substituted Furan-2-carboxaldehydes and Furo[b]pyrrole Type Aldehydes with Benzothiazolium Salts

by Zita Puterová, Alžbeta Krutošíková, Antonín Lyčka and Tatiana Ďurčeková

Molecules 2004, 9(4), 241-255; https://doi.org/10.3390/90400241 - 31 Mar 2004

Cited by 6 | Viewed by 8561

Abstract

A series of new push-pull compounds were synthesised by reaction of 5-aryl- furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with benzothiazolium salts. These new condensation products represent highly conjugated systems that have potential biological activity. The reaction of furo[b]pyrrole type aldehydes with benzothiazolium salts give [...] Read more.

A series of new push-pull compounds were synthesised by reaction of 5-aryl- furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with benzothiazolium salts. These new condensation products represent highly conjugated systems that have potential biological activity. The reaction of furo[b]pyrrole type aldehydes with benzothiazolium salts give potential precursors of cyanine dyes. Full article

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226 KiB

Open AccessArticle

Synthesis and Determination of pKa Values of Some New 3,4-Disubstituted-4,5-Dihydro-1H-1,2,4-triazol-5-one Derivatives in Non-aqueous Solvents

by Haydar Yüksek, Zafer Ocak, Muzaffer Alkan, Sule Bahçeci and Mustafa Özdemir

Molecules 2004, 9(4), 232-240; https://doi.org/10.3390/90400232 - 31 Mar 2004

Cited by 27 | Viewed by 9469

Abstract

3-Alkyl(Aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with 2-furoyl chloride and thiophene-2-carbonyl chloride to afford the corresponding 3- alkyl(aryl)-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) and 3-alkyl(aryl)- 4-(2-thienylcarbonylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4), respectively. The new compounds synthesized were characterized by using IR, 1H-NMR, 13C-NMR and UV spectral data together with elemental analysis. In addition, to [...] Read more.

3-Alkyl(Aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with 2-furoyl chloride and thiophene-2-carbonyl chloride to afford the corresponding 3- alkyl(aryl)-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) and 3-alkyl(aryl)- 4-(2-thienylcarbonylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4), respectively. The new compounds synthesized were characterized by using IR, 1H-NMR, 13C-NMR and UV spectral data together with elemental analysis. In addition, to investigate the effects of solvents and molecular structure upon acidity, compounds 3 and 4 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, N,N-dimethylformamide and acetonitrile). The half-neutralization potential values and the corresponding pKa values were determined for all cases. Full article

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195 KiB

Open AccessArticle

Synthesis and Some Reactions of 3-Chloro-2-(cyanomethylene)-1,2-dihydroquinoxalines

by Craig A. Obafemi and Wolfgang Pfleiderer

Molecules 2004, 9(4), 223-231; https://doi.org/10.3390/90400223 - 31 Mar 2004

Cited by 8 | Viewed by 8473

Abstract

2,3-Dichloroquinoxaline and some of its derivatives have been reacted with malononitrile and ethyl cyanoacetate to yield a variety of 3-chloro-2-(cyanomethylene)- 1,2-dihydroquinoxaline derivatives. The reaction of 3-chloro-2-(dicyanomethylene)-1,2- dihydroquinoxaline (2e) with pyridine and its methyl derivatives led to the zwitterionic structures 6a-6c. The structures of [...] Read more.

2,3-Dichloroquinoxaline and some of its derivatives have been reacted with malononitrile and ethyl cyanoacetate to yield a variety of 3-chloro-2-(cyanomethylene)- 1,2-dihydroquinoxaline derivatives. The reaction of 3-chloro-2-(dicyanomethylene)-1,2- dihydroquinoxaline (2e) with pyridine and its methyl derivatives led to the zwitterionic structures 6a-6c. The structures of the newly synthesized compounds were assigned by spectroscopic data and elemental analyses. Full article

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197 KiB

Open AccessArticle

Structure-Acidity-IR Spectra Correlations for p-Substituted N-Phenylsulfonylbenzamides†

by Alexander Perjessy, Walter M.F. Fabian, Patrik Parik, Miroslav Ludwig, Dusan Loos and Zora Sustekova

Molecules 2004, 9(4), 213-222; https://doi.org/10.3390/90400213 - 31 Mar 2004

Cited by 2 | Viewed by 8720

Abstract

The wavenumbers of the IR absorption bands of the C=O, S=O and N-H stretching vibrations for a series of p-substituted N-phenylsulfonylbenzamides were measured in trichloromethane. The bond orders, Mulliken charges, charge densities and heats of formation were calculated using the PM3 method. Fifty [...] Read more.

The wavenumbers of the IR absorption bands of the C=O, S=O and N-H stretching vibrations for a series of p-substituted N-phenylsulfonylbenzamides were measured in trichloromethane. The bond orders, Mulliken charges, charge densities and heats of formation were calculated using the PM3 method. Fifty significant mutual mono parameter (MP) and six dual parameter (DP) correlations were found for the IR spectral, theoretical structural data, substituent constants and previously reported dissociation constants in five polar organic solvents. The transmission of the substituent effects has been discussed and the solvent effect on the slopes of some linear correlations was evaluated using different solvent parameters. The results showed that the factors describing the electronic structure and controlling the dissociation equilibrium and the IR spectra properties of p-substituted N-phenylsulfonylbenzamides must be the same Full article

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168 KiB

Open AccessArticle

Synthesis of Some New 4,5-Substituted-4H-1,2,4-triazole-3-thiol Derivatives

by M. Koparır, A. Cansız and A. Demirdağ

Molecules 2004, 9(4), 204-212; https://doi.org/10.3390/90400204 - 31 Mar 2004

Cited by 111 | Viewed by 13759

Abstract

In this study appropriate hydrazide compounds, furan-2-carboxylic acidhydrazide (1) and phenylacetic acid hydrazide (2) were converted into 1,4-substitutedthiosemicarbazides 4a-e and 5a-e and 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The 1,4-substituted thiosemicarbazides were then converted into5-(furan-2-yl or benzyl)-4-(aryl)-4H-1,2,4-triazole-3-thiols 8a-e and 9a-e. In addition, theazomethines [...] Read more.

In this study appropriate hydrazide compounds, furan-2-carboxylic acidhydrazide (1) and phenylacetic acid hydrazide (2) were converted into 1,4-substitutedthiosemicarbazides 4a-e and 5a-e and 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The 1,4-substituted thiosemicarbazides were then converted into5-(furan-2-yl or benzyl)-4-(aryl)-4H-1,2,4-triazole-3-thiols 8a-e and 9a-e. In addition, theazomethines 11a-d and 12a-d were prepared from the corresponding arylaldehydes and the4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The structures of allthe synthesized compounds were confirmed by elemental analyses, IR, ¹H-NMR and¹³ C-NMR spectra. Full article

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573 KiB

Open AccessReview

Mechanism-based Enzyme Inactivators of Phytosterol Biosynthesis

by Wenxu Zhou, Zhihong Song, Ragu Kanagasabai, Jialin Liu, Pruthvi Jayasimha, Archana Sinha, Phani Veeramachanemi, Mathew B. Miller and W. David Nes

Molecules 2004, 9(4), 185-203; https://doi.org/10.3390/90400185 - 31 Mar 2004

Cited by 14 | Viewed by 14335

Abstract

Current progress on the mechanism and substrate recognition by sterol methyl transferase (SMT), the role of mechanism-based inactivators, other inhibitors of SMT action to probe catalysis and phytosterol synthesis is reported. SMT is a membrane-bound enzyme which catalyzes the coupled C-methylation-deprotonation reaction of [...] Read more.

Current progress on the mechanism and substrate recognition by sterol methyl transferase (SMT), the role of mechanism-based inactivators, other inhibitors of SMT action to probe catalysis and phytosterol synthesis is reported. SMT is a membrane-bound enzyme which catalyzes the coupled C-methylation-deprotonation reaction of sterol acceptor molecules generating the 24-alkyl sterol side chains of fungal ergosterol and plant sitosterol. This C-methylation step can be rate-limiting in the post-lanosterol (fungal) or post-cycloartenol (plant) pathways. A series of sterol analogs designed to impair SMT activity irreversibly have provided deep insight into the C-methylation reaction and topography of the SMT active site and as reviewed provide leads for the development of antifungal agents. Full article

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Molecules, Volume 9, Issue 4 (April 2004) – 7 articles , Pages 185-263

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