Synthesis and Antioxidant Activity of Bis‐oxazolyl/thiazolyl/imidazolyl 1,3,4‐Oxadiazoles and 1,3,4‐Thiadiazoles

A variety of symmetrical trisheterocycles bis‐oxazolyl/thiazolyl/imidazolylacetamido‐sulfonylmethyl 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles was prepared, and their antioxidant activity was studied. The compounds bisoxazolyl oxadiazole and bisoxazolyl thiadiazole having methyl substituent on the aromatic ring exhibited greater antioxidant activity than the standard ascorbic acid.     

Synthesis and Anti‐allergic Activity of Bis‐heteroaryl Hydrazines

The bis(oxazolyl and/or thiazolyl)hydrazines were prepared, and their anti‐allergic activity was studied. All the compounds displayed variable extent of anti‐allergic activity on immunoglobulin E/silver‐stimulated RBL‐2H3 cells at 50 and 100 μM concentrations. The unsubstituted and chlorosubstituted compounds showed higher activity than those having methyl substituent. Compounds 9c and 10c do not cause cytotoxicity of the cells at 50 and 100 μM and also significantly inhibit β‐hexosaminidase release stimulated by immunoglobulin E/silver at 50 and 100 μM.     

Synthesis of 6-Heterocyclically Appended Tri- O-methyl Protected 6-Desmethyl Emodin Derivatives

A convenient synthesis of several 6-heterocyclically appended tri-O-methyl 6-desmethyl emodin derivatives including the tetrazolyl, oxazolyl, oxazolinyl, benzimidazolyl, benzoxazolyl, and benzothiazolyl derivatives of potential biological and medicinal interest was achieved starting from the tri-O-methyl protected emodin aldehyde or nitrile. In addition, these derivatives could serve as synthons for heterocyclic hypericin derivatives.     

Synthesis and Antimicrobial Activity of Azolyl Pyrimidines

A new class of azolyl pyrimidines linked by diamino sulfone moiety was prepared and studied their antimicrobial activity. Chloro‐substituted and nitro‐substituted thiazolyl pyrimidines ( 9c and 9e ) showed excellent antibacterial activity against Bacillus subtilis , while imidazolyl pyrimidines ( 10c and 10e ) exhibited promising antifungal activity against Aspergillus niger .     

Synthesis of some new azole,azepine, pyridine,and pyrimidine derivatives using 6‐hydroxy‐4H‐4‐oxo[1]‐benzopyran‐3‐ carboxaldehyde as a versatile starting material

Condensation of 3‐formyl chromone 1 with hydroxylamine hydrochloride afforded the corresponding oxime 2 that was converted to nitrile 3 . Refluxing of oxime 2 and/or nitrile 3 with aceturic or hippuric acid gave 16 and 17 . Treatment of 1 with semicarbazide hydrochloride and thiosemicarbazide afforded the corresponding carbazones 5–6 that underwent cyclization with ethyl bromoacetate and/or chloroacetone yielding 7–8 . Also 1 reacted with acyclic active methylene reagents, e.g. malononitrile, ethyl cyanoacetate, and ethyl acetoacetate to form compounds 11, 12 , and 13 . Reaction of 1 with bifunctional reagents, e.g. benzil, o‐phenylenediamine, o‐aminophenol, and o‐aminothiophenol yielding the corresponding imidazolyl bezopyranone and azepine derivatives 14–20 . Condensation of 1 with acyclic or heterocyclic compounds containing active methylene group, e.g. hippuric acid forming the condensed products 21–27 . © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:20–27, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20048     

Synthesis of aromatic oxazolyl‐ and carboxyl‐functionalized polymers: Atom transfer radical polymerization of styrene initiated by 2‐[(4‐bromomethyl)phenyl]‐4,5‐dihydro‐4,4‐dimethyloxazole

The synthesis of a new compound, 2‐[(4‐bromomethyl)phenyl]‐4,5‐dihydro‐4,4‐dimethyloxazole ( 1 ), and its utility in the synthesis of oxazoline‐functionalized polystyrene by atom transfer radical polymerization (ATRP) methods are described. Aromatic oxazolyl‐functionalized polymers were prepared by the ATRP of styrene, initiated by ( 1 ) in the presence of copper(I) bromide/2,2′‐bipyridyl catalyst system, to afford the corresponding α‐oxazolyl‐functionalized polystyrene ( 2 ). The polymerization proceeded via a controlled free radical polymerization process to produce the corresponding α‐oxazolyl‐functionalized polymers with predictable number‐average molecular weights, narrow molecular weight distributions in high‐initiator efficiency reactions. Post‐ATRP chain end modification of α‐oxazolyl‐functionalized polystyrene ( 2 ) to form the corresponding α‐carboxyl‐functionalized polystyrene ( 3 ) was achieved by successive acid‐catalyzed hydrolysis and saponification reactions. The polymerization processes were monitored by gas chromatography analyses. The unimolecular‐functionalized initiator and functionalized polymers were characterized by thin layer chromatography, spectroscopy, size exclusion chromatography, and nonaqueous titration analysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis of 6-Heterocyclically Appended Tri-<Emphasis Type="Italic">O</Emphasis>-methyl Protected 6-Desmethyl Emodin Derivatives

Summary. A convenient synthesis of several 6-heterocyclically appended tri-O-methyl 6-desmethyl emodin derivatives including the tetrazolyl, oxazolyl, oxazolinyl, benzimidazolyl, benzoxazolyl, and benzothiazolyl derivatives of potential biological and medicinal interest was achieved starting from the tri-O-methyl protected emodin aldehyde or nitrile. In addition, these derivatives could serve as synthons for heterocyclic hypericin derivatives.     

Photochemical oxazole-nitrile conversion downstream of rhizoxin biosynthesis and its impact on antimitotic activity

Through metabolic profiling of mutants and wild type of the endofungal bacterium Burkholderia rhizoxinica two novel rhizoxin derivatives with unusual nitrile substitutions were discovered. The nitrile groups result from a photochemical oxidative cleavage of the oxazolyl moiety. In vitro studies revealed that the photooxidation by singlet oxygen also takes place in the absence of a photosensitizer, and that also a thiazolyl-substituted rhizoxin analogue undergoes the same transformation. The resulting nitriles have antimitotic properties but are significantly less active than the parent compounds. These results highlight the impact of photoreactions onto the antiproliferative agent and encourage the introduction of bioisosteric groups that render the compound less susceptible towards photooxidation.     

Synthesis of thiazole,oxazole and heterocyclic ring‐substituted 1,2‐dioxanes

The reactions of 4‐bromoacetyl‐3‐methoxy‐3‐methyl‐6,6‐diphenyl‐1,2‐dioxane with thioureas or thioamides gave 3‐methoxy‐3‐methyl‐6,6‐diphenyl‐4‐(4‐thiazolyl)‐1,2‐dioxanes in 63–90% yields. The similar reaction of 4‐bromoacetyl‐3‐methoxy‐3‐methyl‐6,6‐diphenyl‐1,2‐dioxane with acetamide gave 3‐methoxy‐3‐methyl‐4‐(2‐methyl‐4‐oxazolyl)‐6,6‐diphenyl‐1,2‐dioxane in 39% yields. The reactions of 4‐bromoacetyl‐3‐methoxy‐3‐methyl‐6,6‐diphenyl‐1,2‐dioxane with 3‐alkyl‐4‐amino‐5‐mercaptot[1,2,4]triazoles yielded 3‐methoxy‐3‐methyl‐6,6‐diphenyl‐4‐[3‐(5‐alkyl[1,2,4]triazolo[3,4‐b]‐2,3‐dihydro‐6H‐[1,3,4]thiadiazinyl)]‐1,2‐dioxanes in moderate yields (43–46%).     

Synthesis of furanyl and oxazolyl N‐substituted piperidine and imidazoline salts as potential agonists of M1 muscarinic receptors

Furanyl and oxazolyl N‐substituted imidazoline salts were prepared by reacting furanyl and oxazolyl esters with ethylenediamine and trimethyl aluminum, followed by the addition of methyl iodide or hydrogen chloride. The piperidinium salts were prepared by treating furanyl and oxazolyl chlorides with piperidine base, followed by the addition of methyl iodide or hydrogen chloride.     

Synthesis of substituted 2-amino-4-quinazolinones via ortho-fluorobenzoyl guanidines

A novel route to 12 substituted 2-amino-4-quinazolinones is described. Starting from 2,6-difluoro-4-methoxybenzonitrile, substitution of one of the fluorine atoms either directly or indirectly with heterocycles (e.g., pyridyl, thiazolyl, pyrazolyl) followed by hydrolysis of the nitrile gave a series of o-fluorobenzoic acid derivatives. Condensation with a set of six N,N-disubstituted guanidines followed by base-promoted ring closure afforded 2-amino-4-quinazolinone derivatives.     

Design,Synthesis, and Anticancer Activity of New Oxadiazolyl‐Linked and Thiazolyl‐Linked Benzimidazole Arylidines,Thioglycoside, and Acyclic Analogs

2‐[(4‐Thiazolylmethyl)thio]‐1H‐benzimidazole 3 was prepared and was allowed to react with ethyl chloroactate then with hydrazine hydrate to afford the hydrazide derivative 5 , which was then reacted with aromatic aldehydes to afford the corresponding arylidine derivatives 6 – 9 . Heterocyclization of the latter hydrazones with acetic anhydride afforded the substituted 1,3,4‐oxadiazoline derivatives 10 – 13 . In addition, new ((thiazolyl)imidazolyl) oxadiazole thioglycoside and acyclic‐C nucleoside analog were prepared via heterocylization of the hydrazide 5 then glycosylation with α‐acetobromoglucose or condensation with D‐xylose, respectively. All the new compounds were structurally characterized. The anticancer activity of some of the newly synthesized compounds was studied against human breast cancer cells (MCF‐7). The results of the anticancer activity showed that compounds 8 , 11 , 12 , 17 , and 18 revealed high activities superior to Doxorubicin; however, the other derivatives showed moderate to low inhibition activities against human breast cancer cells. Docking studies into CDK2 enzyme were investigated, which supported the anticancer activity results.     

A Facile and Effective Procedure for Synthesis of Polyfunctionalized Bis (imidazolyl) Pyrrole/Imidazolyl Indole from Pyrrole/Indole with Arylglyoxals and N‐aryl amidines

Heterocyclic systems containing bis (imidazolyl) pyrrole or imidazolyl indole moieties were synthesized by heterocyclization of pyrrole or indole with arylglyoxal monohydrates and N‐aryl amidines in ethanol catalyzed by FeCl₃ at room temperature. The paper reports a facile, efficient, and environmentally friendly protocol for the synthesis of new products. Products were isolated by simple filtration, and their structures were established from their spectroscopic data.     

Synthesis of 2-Aminoindole Derivatives with Hantzsch Ester Catalyzed by Pd/C

Catalytic hydrogenation of 2‐cyano‐2‐(2‐nitrophenyl)acetates bearing an electron withdrawing substituent to the nitrile, using Hantzsch ester catalyzed by Pd/C, affords 2‐aminoindoles in good to excellent yields.     

Synthesis of 9‐[1‐benzyl‐5‐(alkylsulfonyl)‐1H‐2‐imidazolyl]perhydro‐1,8‐acridinediones

Tricyclic dihydropyridines like ZM244085 are potential K_ATP channel openers. In this study 3‐cyanophenyl ring of ZM244085 was replaced with imidazolyl ring. So, 9‐[1‐benzyl‐5‐(alkylsulfonyl)‐1H‐2‐imidazolyl]perhydro‐1,8‐acridinediones ( 5d‐f ) were synthesized from 2‐alkylsulfonyl‐1‐benzyl‐5‐formylimidazole ( 4d‐f ) and cyclohexane‐1,3‐dione according to classical Hantzch synthesis as potential potassium channel modulators.     

Isothiourea‐Mediated Asymmetric O‐ to C‐Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies

The structural motif within a series of tetrahydropyrimidine‐based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic ¹⁹F NMR experiments used to develop a mechanistic understanding of this transformation.     

On the modification of the nitrile groups of acrylonitrile/butadiene/styrene into oxazoline in the melt

Oxazoline functionality is well known to be highly reactive toward a lot of other functional groups like carboxyls, hydroxyls, mercaptans, and amines. In this work we report the possibility to modify the nitrile groups of an acrylonitrile/butadiene/styrene (ABS) copolymer into oxazoline in the molten state in the presence of aminoethanol as modifier agent and zinc acetate as a catalyst. The reaction has been carried out in a batch mixer and in a corotating twin screw extruder. The conversion of the nitrile groups into oxazoline has been verified by infrared spectroscopy, NMR analysis microanalysis and confirmed by thermomechanical characterization. The results indicate that the kinetic of grafting is fast and the conversion of the nitrile groups into oxazoline relatively high, encouraging the use of this modified polymer in the reactive compatibilization of ABS‐based blends. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1795–1802, 2000     

Novel compounds for the synthesis of cefdinir

Preparation of two new compounds 2‐mercapto‐5‐methyl‐1,3,4‐thiadiazolyl‐(Z)‐2‐(2‐amino‐4‐thiazolyl)‐2‐trityloxyiminoacetate ( 14 ) and 2‐mercapto‐5‐methyl‐1, 3,4‐thiadiazolyl‐ (Z)‐2‐(2‐amino‐4‐thiazolyl)‐2‐acetyloxyiminoacetate ( 12 ) and their use in the preparation of 7β‐[(Z)‐2‐(2‐amino‐4‐thiazolyl)‐2‐hydroxyiminoacetamido]‐3‐vinylcephem‐4‐carboxylic acid, also known by the generic name Cefdinir ( 1 ) has been accomplished in a single step by coupling with 7‐amino‐3‐vinylcephem‐4‐carboxylic acid ( 7 ) with purity of greater than 99% by HPLC.     

Approaches to installing a N-gem-dimethylmethylene-2-oxazolyl group and application to the synthesis of a second generation HIV protease inhibitor

Two syntheses of the title compound 1 were developed based on different approaches for installing the oxazole ring moiety. Formation and dehydration of ketoamide was initially used and scaled up to afford 1 on several kilogram scale, then oxazolyl anion/iminium coupling reaction was developed for a more convergent approach.     

Synthesis,Docking, and Anticancer Activity of New Thiazole Clubbed Thiophene,Pyridine, or Chromene Scaffolds

2‐Cyanoacetamido‐4‐methylthiazole ( 1 ) was utilized as a versatile precursor for the construction of new thiazole clubbed thiazolidine, thiophene, pyridine, or chromene scaffold. The base‐catalyzed addition of 1 to phenyl isothiocyanate followed by subsequent treatment of the produced thiocarbamoyl intermediate with ethyl chloroacetate or chloroacetonitrile furnished the corresponding thiazolyl‐thiazolidine and thiazolyl‐thiophene hybrids. The reactions of compound 1 with chemical reagents, namely, acetylacetone, malononitrile, and/or 2‐(4‐anisylidene)‐malononitrile have been studied and furnished the corresponding thiazole‐pyridine hydrides 8 – 10 . Furthermore, treatment of the precursor 1 with salicylaldehyde, various aryl diazonium chlorides, and/or aromatic aldehydes afforded their corresponding thiazolyl‐chromene hybrid 12 , arylhydrazono‐nitriles 13 , and unsaturated nitriles 14 , respectively. The cytotoxicity of the synthesized compounds was screened against the cell lines HepG2, HCT‐116, and MCF‐7. Compounds 8 , 10 , and 12 recorded the best results, which was illustrated by molecular docking. Molecular Operating Environment molecular docking calculations carried out here is to rationalize correlation between docking results and biological data of thymidylate synthase (Protein Data Bank code: IHVY) inhibition. Docking has been carried out in the same co‐crystallographic inhibitor binding site to predict if the binding mode of active compounds is analogous to that of native inhibitor.