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

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Research

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Open AccessArticle Synthesis of Some New 4,5-Substituted-4H-1,2,4-triazole-3-thiol Derivatives
Molecules 2004, 9(4), 204-212; doi:10.3390/90400204
Received: 11 July 2003 / Revised: 9 February 2004 / Accepted: 2 February 2004 / Published: 31 March 2004
Cited by 29 | PDF Full-text (168 KB) | HTML Full-text | XML Full-text
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, [...] 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
Open AccessArticle Structure-Acidity-IR Spectra Correlations for p-Substituted N-Phenylsulfonylbenzamides†
Molecules 2004, 9(4), 213-222; doi:10.3390/90400213
Received: 17 September 2003 / Revised: 12 February 2004 / Accepted: 8 March 2004 / Published: 31 March 2004
Cited by 1 | PDF Full-text (197 KB) | HTML Full-text | XML Full-text
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. [...] 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
Open AccessArticle Synthesis and Some Reactions of 3-Chloro-2-(cyanomethylene)-1,2-dihydroquinoxalines
Molecules 2004, 9(4), 223-231; doi:10.3390/90400223
Received: 16 December 2003 / Revised: 11 February 2004 / Accepted: 20 February 2004 / Published: 31 March 2004
Cited by 4 | PDF Full-text (195 KB) | HTML Full-text | XML Full-text
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 [...] 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
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
Molecules 2004, 9(4), 232-240; doi:10.3390/90400232
Received: 12 June 2003 / Accepted: 11 March 2004 / Published: 31 March 2004
Cited by 21 | PDF Full-text (226 KB) | HTML Full-text | XML Full-text
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, [...] 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
Open AccessArticle Reactions of Substituted Furan-2-carboxaldehydes and Furo[b]pyrrole Type Aldehydes with Benzothiazolium Salts
Molecules 2004, 9(4), 241-255; doi:10.3390/90400241
Received: 18 February 2004 / Accepted: 23 March 2004 / Published: 31 March 2004
Cited by 4 | PDF Full-text (201 KB) | HTML Full-text | XML Full-text
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 [...] 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
Open AccessArticle Preparation of New 2,3-Diphenylpropenoic Acid Esters – Good Yields Even for the More Hindered Z Isomers
Molecules 2004, 9(4), 256-263; doi:10.3390/90400256
Received: 8 March 2004 / Accepted: 18 March 2004 / Published: 31 March 2004
Cited by 2 | PDF Full-text (97 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] 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

Review

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Open AccessReview Mechanism-based Enzyme Inactivators of Phytosterol Biosynthesis
Molecules 2004, 9(4), 185-203; doi:10.3390/90400185
Received: 27 February 2004 / Accepted: 8 March 2004 / Published: 31 March 2004
Cited by 8 | PDF Full-text (573 KB) | HTML Full-text | XML Full-text
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 [...] 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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