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Various Derivatives (various + derivative)
Selected AbstractsPyranopyrazoles III synthesis of 1H -pyrano[2,3- c]pyrazol-4-ones,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2001Misbahul Ain Khan Various derivatives of title ring system were synthesized by Claisen condensation of 4 acetyl-5 -hydroxy-pyrazoles with appropriate esters, followed by acid-catalyzed ring closure. [source] Synthetic and Spectroscopic Investigation of N -Acylated Sulfoximines,CHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2004Christian P. R. Hackenberger Dr. Abstract N -Acylated sulfoximines display unique chemical properties. Various derivatives have been synthesized and investigated by NMR and IR spectroscopy. The results of these studies suggest that the bond between the sulfoximine nitrogen atom and the carbonyl group has a less pronounced double-bond character than the corresponding bond in an amide. This assumption is supported by the first X-ray crystal structure of a sulfoximidoyl derivative. Ab initio calculations (MP2/6-311++G**) provide further insight into the electronic nature of the N -acyl fragment. Studies of the chemical behavior of N -acylated sulfoximines indicate the presence of a highly electrophilic carbonyl group. Thus, the NC(O) bond can easily be cleaved under mild basic conditions, and the acidity of the hydrogen atoms , to the sulfoximine carbonyl group is high. As a consequence of the latter property, endo,endo -sulfoximidoyl norbornene derivatives readily isomerize to their endo,exo counterparts, and sulfoximine-containing pseudopeptides can easily epimerize at the stereogenic center next to the NC(O) carbonyl group. [source] Syntheses of some new 1H -pyrazole, pyridazin-3(2H)-one, and oxazin-4-one derivativesHETEROATOM CHEMISTRY, Issue 1 2006Esvet Akba The new 1H-pyrazole-3-carboxylic acid 2, pyridazin-3(2H)-one 3, and their various derivatives were prepared by the reactions of the 4-benzoyl-5-phenyl-2,3-dihydro-2,3-furandione 1 and 2,5-dichlorophenylhydrazine. Pyrazolo[3,4-d]pyridazine 7 was obtained from cyclization of the pyrazole-3-carboxylic acid 2 with 2,5-dichlorophenylhydrazine. The reaction of 1 and pyrazole-3-carbonitriles 6 gave the new oxazin-4-one 9 derivatives. The structures of compounds were characterized on the basis of elemental analyses, mass, IR, 1H, and 13C NMR spectra. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:8,12, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20170 [source] Chemical modification of chitosan: synthesis and biological activity of new heterocyclic chitosan derivativesPOLYMER INTERNATIONAL, Issue 2 2008Mohamed EI Badawy Abstract BACKGROUND: Numerous works have been published on the chemical modification of chitosan; this polymer is still being modified, leading to various derivatives with improved properties. In the present study, heterocyclic aldehydes including furan-2-carbaldehyde, 5-methylfuran-2-carbaldehyde, 3-pyridine carboxyaldehyde, benzo[d][1,3]dioxole-5-carbaldehyde and 4-oxo-4H -chromene-3-carbaldehyde were reacted with chitosan by a reductive alkylation reaction to produce for the first time five new N -heterocyclic chitosan derivatives to improve the biological activity of chitosan against the most important economic plant pests including fungi and insects, in particular the cotton leafworm Spodoptera littoralis. RESULTS: The chemical structures of the synthesized compounds were confirmed by 1H NMR spectroscopy and the degree of substitution ranged from 0.30 to 0.43. The fungicidal assessment was investigated in vitro using a mycelia radial growth inhibition technique against soil-borne pathogenic fungi Fusarium oxysporum and Pythium debaryanum and the rice leaf blast Pyricularia grisea. The results showed that N -[(5-methylfuran-2-yl)methyl] chitosan was the most active against P. grisea with an EC50 value of 0.919 mg mL,1 while N -(benzo[d][1,3]dioxol-5-ylmethyl) chitosan and N -(methyl-4H -chromen-4-one) chitosan exhibited the most potent fungicidal activity against P. debaryanum and F. oxysporum. An insecticidal bioassay against the larvae of S. littoralis showed that N -(methyl-4H -chromen-4-one) chitosan exhibited a significant growth inhibition and antifeedant activity among the synthesized compounds. CONCLUSION: The chemical modification of chitosan molecule with a heterocyclic moiety led to an enhancement in the biological activity against the plant pathogenic fungi F. oxysporum, P. debaryanum and P. grisea and the cotton leafworm insect S. littoralis. Copyright © 2007 Society of Chemical Industry [source] | ||||||||||