Synthesis of chiral linear and macrocyclic candidates: III. Synthesis and antimicrobial activity of linear tetrapeptide and macrocyclic pentapeptide Schiff bases

Russian Journal of General Chemistry - A series of tetrapeptide Schiff bases and a macrocyclic pentapeptide were synthesized using N α-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl acid...     

Synthesis of chiral linear and macrocyclic candidates: II. Synthesis and investigation of 3,5-bis-linear and macrocyclic tetrapeptide Schiff base pyridine derivatives

Russian Journal of General Chemistry - A series of several linear and macrocyclic tetrapeptide derivatives based on N α-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl] acid hydrazide as starting...     

Synthesis,characterization and antibacterial activity of some new pyrazole based Schiff bases

In the present study a series of new Schiff bases were synthesized. All the synthesized compounds were characterized by IR, ¹H NMR, mass spectral and elemental analyses. Newly synthesized compounds were screened for their antibacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) activity. The results revealed that, compounds 3f and 3c have exhibited significant biological activity against the tested microorganisms.     

Synthesis and antibacterial activity of Schiff bases of 5-substituted isatins

Based on the existing reports on the bioactive isatin derivatives, a number of Schiff bases were synthesized by reacting 5-substituted isatins with bioactive amines/hydrazides and their structures were confirmed using spectroscopic methods such as NMR, IR and mass spectrometry. Furthermore, Nbenzylation of isatin followed by the Schiff base formation furnished a new series of compounds(11a–13c) which allowed the analysis of the effect of isatin N-substitution on the bioactivity of the resulting compounds. The antibacterial activity of the synthesized derivatives was evaluated using a microtiter plate method on a series of gram positive and gram negative bacterial strains. Compounds 2d, 3b, 5c and 6a were among the most potent derivatives against Pseudomonas aeruginosa(MIC = 6.25 μg/m L).Analysis of the structure–activity relationship showed that the incorporation of(thio)urea-based Schiff bases lead to more potent derivatives with a broader spectrum of antibacterial activity. In addition,highly lipophilic compounds such as 11a–12c did not show any measurable antibacterial activity, which implies that an optimal lipophilicity might be an important requirement for the antibacterial activity of the studied isatins. Finally, the finding that hydantoin derivatives of N-benzylisatins(13a–13c) still exhibit some antibacterial activity prompted us to consider exploring the bioactivity of more diverse derivatives of isatin-aminohydantoin Schiff bases(compounds 1a–1d) in our future studies.     

Synthesis,spectral and redox properties of metal complexes of macrocyclic tetraaza chiral Schiff bases

New transition metal(II) coordination compounds of tetraaza macrocyclic chiral Schiff bases, derived from 2-hydroxybenzylideneacetylacetone or 4-hydroxybenzylideneacetylacetone and (1R, 2R)-(–)-1,2-diaminocyclohexane, have been prepared and characterised spectroscopically and electrochemically. E.p.r. spectral data for the Cu^II complexes reveal a strong metal-to-ligand -interaction in their square-planar configuration and the broadening of the g component is due to the strain created by 1R and 2R groups in the cyclohexane rings. The cyclic voltammetric (c.v.) data of the copper complexes show an unusual oxidation state of Cu^III, while Co^II complexes show a reversible Co^II/Co^III redox peak along with an additional peak in the negative potential region characteristic of reversibly bound oxygen. The c.v. results reveal that both Cu^II and Co^II complexes bind axially with added bases. The spectroscopic results reveal that copper, cobalt and nickel complexes are in square-planar geometry, whereas manganese is in octahedral geometry.     

Synthesis,spectroscopic characterization and catalytic activity of cis-dioxidomolybdenum (VI) complexes with chiral tetradentate Schiff bases

New chiral mononuclear cis-dioxidomolybdenum (VI) complexes, MoO ₂ L ¹ –MoO ₂ L ¹⁰ , with tetradentate Schiff bases derived from various substituted salicylaldehydes and 1S,2S-(+)-2-amino-1-(4-nitrophenyl)-1,3-propanediol were synthesized. All complexes were characterized by elemental analysis, circular dichroism, electronic and IR spectroscopy. ¹H NMR and also two-dimensional (COSY, NOESY and gHSQC) NMR measurements made for MoO ₂ L ¹ –MoO ₂ L ¹⁰ complexes show that Schiff bases are coordinated to the MoO₂²⁺ cation, creating facial (fac) and meridional (mer) types of geometrical isomers. Moreover, catalytic activity studies were also performed for all complexes in asymmetric sulfoxidation of thioanisole and epoxidation of styrene, cyclohexene and two monoterpenes, i.e. S(−)-limonene and (−)-α-pinene, using aqueous 30% H₂O₂ or tert-butyl hydroperoxide as the oxygen source.     

Synthesis of new macrocyclic chiral manganese(III) Schiff bases as catalysts for asymmetric epoxidation

We describe a general synthetic strategy for the preparation of a series of macrocyclic chiral manganese(III) salen complexes. The developed reaction pathway allows the modulation of the different key groups, namely, the chiral diimine, the bulky substituents in positions 3 and 3', and the linker used in the macrocyclization of the Schiff base. The different complexes presented here illustrate these readily available structural variations. The catalytic properties of the catalysts (5 mol %) were improved for the asymmetric epoxidation of 2,2'-dimethylchromene with NaOCl or H2O2 as oxygen atom donor. A large range of enantiomeric excesses was obtained (ee values from 30% to 96%), depending on the features and the stability of the complexes. The most efficient catalyst, in terms of stereoinduction (ee value = 96%), contains a diiminocyclohexyl moiety, ethyl groups in positions 3 and 3', and a short polyether junction arm.     

Synthesis and antibacterial evaluation of fused pyrazoles and Schiff bases

Abstract

For the discovery of new antibiotic drugs to face the problem of microbial resistance, a series of fused pyrazoles such as pyrazolopyrimidines 15a–f, pyrazoloquinazolines 18a, b and pyrazolotriazines 20a, b was synthesized via the reaction of 5-aminopyrazoles 8a, b with 3-(dimethylamino)-1-aryl-prop-2-en-1-ones 9a–d, 2-((dimethylamino)methylene)-5,5-dimethylcyclohexane-1,3-dione (16) and sodium nitrite (NaNO₂), respectively. Finally, Schiff bases 22a–g were obtained by the condensation of 8a, b with aromatic aldehydes 21a–d. The chemical structure of the new compounds was confirmed by spectroscopy. The structure of 15?b was confirmed by X-ray crystallography analysis. All compounds were screened for antibacterial properties toward multi-drug resistant bacteria (MDRB).     

氯取代二苯基苯甲酰基吡唑酮席夫碱的合成与抑菌活性

酰基吡唑啉酮及其席夫碱是一类杂环β─二酮螯合剂。其活性的双酮配位基可以同多种金属或稀土离子形成大量的配合物,是金属和稀土离子良好的萃取剂和螯合剂[1~5],是一类优良的荧光材料中间体,同时表现出一定的抗菌、抗病毒性能[6~11],目前在药理、生物活性试剂、冶金、染料、发     

三氮唑类席夫碱的合成及其荧光性能

近年来,Schiff碱因其结构的多样化以及具有光、电、磁等物理材料性能[1-3]的配位化学性能[4-5]等引起人们的关注,同时一些特殊结构的Schiff碱的合成和性质研究具有更为重要的理论意义和应用价值.     

Synthesis and antimicrobial activity of some novel ferrocene-based Schiff bases containing a ferrocene unit

In the present investigation, a series of ferrocene-based Schiff bases 5a?Cm were synthesized by the condensation of various chalcones 3a?Cm with S-benzyl dithiocarbazate in absolute ethanol using catalytic amount of glacial acetic acid, and characterized by element analysis,¹H NMR,¹³C NMR, and IR. The synthesized compounds were screened for their in vitro antimicrobial activity against four bacterias (Staphylococcus aureus ATCC 9144, Bacillus cereus ATCC 11778, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 43288) and two fungals (Aspergillus niger ATCC 9092 and Aspergillus fumigatus ATCC 46645) strains. The Schiff bases 5g, 5h, and 5m against Gram-positive bacterial (E. coli and P. aeruginosa) strains was found to be higher than that for the standard drug. They are potential new drugs in antibacterial activity aspects in further days.     

Synthesis of novel azo Schiff bases and their antibacterial and antifungal activities

Ten new azo Schiff bases 5a-h and 7a-b were prepared in excellent yields via the condensation of different aromatic amines and a new azoaldehyde, 2-hydroxy-3- methoxy-5-(4-methoxyphenylazo)benzaldehyde (4) by two different methods. All new compounds were tested against five microorganisms: Staphylococcus aureus (Gram positive and methicillin resistant), Bacillus subtilis (Gram positive), Kelebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli (all Gram negative). Compounds 4, 5a, 5c, 5d and 5g were moderately active against Staphylococcus aureus and Bacillus subtilis. Compound 7b was highly active against Bacillus subtilis and moderately active against Staphylococcus aureus. Other compounds were inactive against these strains of bacteria. The antifungal activities of these compounds were also tested against eight different fungal species. None of them were active against the fungi species tested.     

Synthesis of new chiral Schiff bases from (+)-2-carene

New chiral Schiff bases were synthesized through tricyclic 2-azetidinones as key intermediate products which were obtained by reaction of (+)-2-carene with chlorosulfonyl isocyanate.     

Synthesis and biological activity of sulfur-containing aryl-aldehyde Schiff bases

A series of chemically modified aryl-aldehyde Schiff bases has been synthesized and tested for their antioxidant activity and radiation protection. We observed that disulfide-containing aryl-aldehyde Schiff base 6c exhibited potent free radical scavenging, antioxidation, and radioprotection activities.     

Synthesis,characterization and antibacterial activity of indium(III) complexes with adamantane-ring containing Schiff bases

Indium(III) chloride tetrahydrate and Schiff-base ligands derived from adamantaneamine and 3-/4-methoxysalicylaldehyde gave two complexes, C₂₂H₃₂Cl₃InN₂O₃ (1) and C₃₆H₄₄C_l3InN₂O₄ (2), respectively. The complexes were characterized by IR, ¹H NMR, elemental analysis, molar conductance, thermal analysis, and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic system, P2₁/n space group with the asymmetric unit consisting of one indium(III), one N-(3-methoxysalicylidene)-aminoadamantane (L¹), three chlorides and one N,N-dimethylformamide molecule. The indium is six-coordinate with reversed triangular-prism geometry via three oxygens and three chlorides. Complex 2 crystallizes in the triclinic system, P 1 space group; the asymmetric unit consists of one indium(III), two N-(4methoxysalicylidene)-aminoadamantane (L²), and three chlorides. The indium is five-coordinate with distorted trigonal-bipyramidal geometry via two oxygens and three chlorides. Antibacterial activities of the complexes have been investigated against Escherichia coli and Staphylococcus aureus.     

Synthesis,structure and characterization of some Schiff bases bearing phenylferrocene

Some novel Schiff bases bearing phenylferrocene were synthesized by condensation reaction of 4‐ferrocenylaniline with different aromatic aldehydes. The compounds prepared were characterized by spectroscopic methods (IR, UV–visible, ¹H and ¹³C NMR) and elemental analysis. The single crystal analysis of compound F1 [monoclinic, space group, P2₁/c (no. 14), a = 19.858(2), b = 7.416(2), c = 12.095(5) Å, β = 106.257(14) ] indicates a trans imine bond with a bond length of 1.270(2) Å, typical of a carbon‐nitrogen double bond. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and characterization of some nickel(II) Schiff bases complexes

Summary The reaction of nickel(II) salts with 2-picolyl- and 2,6-lutidyl-phenylketone benzoylhydrazone and theirp-nitro- andp-methoxy-derivatives were carried out and the compounds characterized on the basis of analytical and spectral data.     

Synthesis and anti-bacterial activities of some novel Schiff bases derived from aminophenazone

A series of 1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one-containing Schiff bases were synthesized, characterized and screened for their antibacterial activities. The structures of the synthesized compounds were established by spectroscopic (FT-IR, 1H-NMR, 13C-NMR, MS) and elemental analyses. The anti-bacterial activities (with MIC values) of compounds were evaluated. The anti-bacterial screening results reveal that among the six compounds screened, four compounds showed moderate to good anti-bacterial activity. Among the tested compounds, the most effective compounds against four bacterial strains, viz. Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Streptococcus pyogenes, are [(2-chlorobenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one (4) and [(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylimino)methyl]benzonitrile (5) with MIC values of 6.25 μg/mL.