Syntheses of new difluoromethylene benzoxazole and 1,2,4-oxadiazole derivatives, as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

In an effort to prepare new fluorine-containing compounds, which are active against HIV, several chemical modifications of a series of benzoxazole and 1,2,4-oxadiazole-CF₂CHOHAr derivatives were carried out. The products (9-30) which all have one or two CF₂ groups were tested for activity against HIV-1; they were devoid of significant activity, one of them being cytotoxic.     

Synthesis of benzoxazole sulfanilamide derivatives

A number of hitherto undescribed 2-(p-aminobenzenesulfamide) benzoxazoles are prepared by treating 2-aminobenzoxazole or its 6-substituted compounds with p-carbomethoxyaminobenzenesulfochloride or p-acetylaminobenzenesulfochloride, followed by alkaline hydrolysis. A similar reaction with 6-amino-2-hydroxy- and 2-mercaptobenzoxazoles gives 6-(p-aminobenzenesulfamido)-2-hydroxy- and 2-mercaptobenzoxazoles.The work was done by E. N. Padeiska of the Chemotherapy Division of VNIKhFI (All-Union Pharmaceutical Chemistry Research Institute).     

Syntheses and biological properties of new 8-fluorocarbapenem derivatives

8-Fluorocarbapenem derivatives having various C-3 side chains were synthesized to study for the structure-activity relationship of carbapenems by in vitro biological evaluation. The introduction of fluorine at C-8 of racemic PS-5 led to slight improvements of the antimicrobial activity and the stability to renal dehydropeptidase-I. When D-cysteine was additionally introduced to the C-3 position of (+/-)-8-fluorocarbapenem, the diastereomeric separation of the 8-fluorocarbapenems became feasible. As expected from penicillins and cephalosporins, (+)-8-fluoro-3-D-cysteinylcarbapenem (+)-7a was antimicrobially active, whereas (-)-7b was inactive. It is worth noting, however, that (+)-7a was significantly more sensitive to renal dehydropeptidase-I than (-)-7b. Irrespective of the presence of fluorine at C-8, basic S-side chains at C-3, such as the pyridyl and pyrrolidyl groups, significantly improved in antimicrobial activity and dehydropeptidase-I stability. The combination of 8-fluorination with C-3 basic side chains in 7c--g resulted in a marked improvement of antimicrobial activity and dehydropeptidase-I stability.     

Iron(III) complexes with benzoxazole derivatives

Summary Iron(III) complexes of the general formula Fe(L)_nX₃·mH₂O, where L=benzoxazole(benzox), 2-methylbenzoxazole(2-Mebenzox), 2, 5-dimethylbenzoxazole(2, 5-diMebenzox); n=2, 3, 4, 6; X=Cl, Br, NO₃ or ClO₄; m=0, 1, 2, 5, have been prepared and studied by chemical analysis, magnetic moments, i.r., electronic, Mössbauer spectra and molar conductivity values.The oxazoles are N_ring bonded and the complexes are hexacoordinate in the solid state with exception of the five-coordinate Fe(2, 5-diMebenzox)₂Br₃.     

Syntheses of quinoline derivatives

In order to study the relationship between structure and biological activity we have synthesized 5-alkoxymethyl- and 5-aryloxymethyl-7-bromo-8-quinolinols.For part II, see [1].     

Syntheses of tetraoxaquaterene derivatives

Several new dimethyl and tetramethyl tetraoxaquaterenes, 3d and 3e , have been prepared in order to synthesize the oxygen analogues of porphyrin. The reaction between furan and a ketone using an acidic catalyst gave the cyclic tetramer, tetraquaterene, and oligomers. On the other hand, in the case of furan and an aldehyde, only linear oligomers were isolated. The condensation of furan-containing dimers with carbonyl compounds, both ketone and aldehyde, except formaldehyde, gave the tetraoxaquaterene. In the case of formaldehyde, the yield of cyclic tetramer was negligible.     

Intramolecular single and double proton transfer in benzoxazole derivatives

The “double” derivatives of benzoxazole, bis-2,5-(2-benzoxazolyl)hydroquinone (II) and bis-3,6-(2-benzoxazolyl)-pyrocatochol (III), have been investigated. In (II), only one proton is transferred in the S₁ state. Primary and tautomeric forms exist in a rapidly established equilibrium. In (III), two tautomers were detected. One is generated in the S₁ state by a double proton transfer without a potential barrier, while the other, generated by a single proton transfer, is already present in trace amounts in the S₀ state.     

Efficient one-pot synthesis of benzoxazole derivatives catalyzed by Zinc triflate

A simple and efficient method has been developed for the synthesis of benzoxazoles from 2-aminophenol and substituted aldehydes in the presence of a catalytic amount of zinc triflate in ethanol solvent at reflux temperature.     

Improved mesophase stability of benzoxazole derivatives via dipole moment modification

By modifying the molecular dipole moments with lateral monofluorine substituent, improved mesophase stabilities were obtained for novel benzoxazole derivatives, 2-(4?-alkoxy-3-fluorobiphenyl-4-yl)-benzoxazole liquid crystals (coded as nPPF(3)Bx). The series of nPPF(3)Bx with lateral monofluorine substituent ortho to benzoxazole group have larger calculated dipole moments by about 2 D than the corresponding fluorine-substituted analogs (compounds I) with lateral monofluorine ortho to alkoxy group; it is interesting to note that they show lower melting and clearing points but better mesophase stability with wider mesophase ranges for the molecules with both polar (NO₂, Cl) and nonpolar (CH₃, H) terminal groups. Meanwhile, compounds nPPF(3)Bx show greater red-shifted photoluminescence emissions than compounds I, which suggest that π–π interaction between molecules is reinforced by the enhanced dipole–dipole interaction caused by increased dipole moments. These results suggest that modification of the molecular dipole moment is an effective method to improve the mesophase stability of the classical mesogenic compounds.     

Amphiphilic ESIPT benzoxazole derivatives as prospective fluorescent membrane probes

Fluorescent amphiphilic benzoxazole derivatives were synthesized and used to produce photoactive phosphatidylcholine (PC) liposomes by reserve-phase evaporation. The dyes absorbed in the UV region and were fluorescent in the blue-green region (determined by solvent polarity). The alkyl chain length seemed to play a fundamental role in the photophysics of the benzoxazole fluorophore in reverse liposomes, and despite the same ESIPT core and phospholipid building block, each amphiphilic dye had a particular emission profile related to the dye location in the liposome. The fluorescence emission spectra from dye 5 showed that its fluorophore experienced a polar environment, due to the single normal emission, while dyes 6–7 had (in part) a normal emission, and the main fluorescent band ascribed to the ESIPT emission indicated a more hydrophobic environment. Despite the complex fluorescent profiles, the benzoxazole derivatives could be successfully introduced into the reverse liposome structure due to the interaction between the alkyl chain and PC bilayer.     

Syntheses and properties of new photochromic diarylethene derivatives having a pyrazole unit

New photochromic diarylethenes 1a, 2a and 3a bearing a pyrazole unit have been synthesized. Their properties, including photochromic reactivity, fluorescence and electrochemical properties were investigated. These compounds showed good photochromic properties, high cycloreversion quantum yield and relatively strong fluorescence. The cycloreversion quantum yields of 1a, 2a and 3a are 0.46, 0.53 and 0.57, respectively, which are larger than those of their cyclization quantum yields (0.43, 0.45 and 0.47, respectively). The oxidations of diarylethenes 1a, 2a and 3a were initiated at 0.73, 1.11 and 0.79 V, respectively. Moreover, the position of the methoxyl substituent had remarkable impacts on the above optical and electrochemical properties.     

Syntheses of polymerizable hydroquinone derivatives

Several polymerizable hydroquinone derivatives were prepared by the Williamson synthesis. Thus, hydroquinone mono(p-vinylbenzyl) ether (III-1), hydroquinone methyl p-vinylbenzyl ether (III-4), and hydroquinone benzyl p-vinylbenzyl ether (III-5), tert-butylhydroquinone mono(p-vinylbenzyl) ether (III-2), and 2,5-di-tert-butylhydroquinone mono(p-vinylbenzyl) ether (III-3) were synthesized by the reactions of p-chloromethylstyrene with the corresponding hydroquinone derivatives in alcoholic potassium hydroxide or with their potassium salts in dipolar aprotic solvents. All monomers were found to polymerize by free-radical initiation except III-3, which required a cationic initiator.     

A new method of synthesis of some 2-aryl and 2-heterocyclic benzimidazole,benzoxazole and benzothiazole derivatives

A new one-step facile method for the synthesis of some benzimidazole, benzoxazole and benzothiazole derivatives is described. The method involves the action of aromatic and heterocyclic selenoamides on some o-phenylenediamine, o-aminophenol and o-aminothiophenol and their derivatives.     

Synthesis,molecular modeling,and pharmacological evaluation of new 2-substituted benzoxazole derivatives as potent anti-inflammatory agents

Structural Chemistry - In the present work, 2-substituted benzoxazole derivatives were synthesized from 2-(benzo[d]oxazol-2-yl) aniline. All the synthesized compounds were purified and...     

Enantioselective chromenone benzoxazole receptor for glutamic acid and its derivatives

Combination of a binaphthyl unit with chromenone benzoxazole fragments provided a chiral receptor that is enantioselective for glutamic acid and its derivatives. The receptor racemic mixture was resolved by TLCs impregnated with (R,R)-thiodilactic acid. High association constants were measured for dansylglutamic acid, using a fluorescent method. This receptor can be used for the resolution of the tosylglutamic acid racemic mixture.     

Synthesis and mesomorphic properties of benzoxazole derivatives with lateral multifluoro substituents

Fluorinated aromatics is generally chosen as mesogenic cores to design novel liquid crystal compounds. Here, a series of benzoxazole derivatives with laterally multifluorinated biphenyl units, 2-(3′,3-difluoro ?4′-alkoxy-1,1′-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(3)PF(3)Bx), are synthesized and characterized, where methyl and nitro moieties are selected as terminal groups to investigate the effects of different polar substituents on the liquid crystal properties. The compounds nPF(3)PF(3)Bx show enantiotropic mesophases with mesophase ranges of 0–40°C and 0–63°C on heating and cooling for hydrogen-terminated derivatives (nPF(3)PF(3)BH), 43–93°C and 54–123°C for methyl-terminated ones (nPF(3)PF(3)BM), 60–108°C and 74–152°C for nitro terminated ones (nPF(3)PF(3)BN), respectively. They exhibit photoluminescence emission peaks at 390–392 nm and UV–vis absorption bands with maxima at 327–330 nm, respectively. The results reveal that lateral multifluoro substituents lead to a decrease in melting/clearing points, while electron-withdrawing terminal nitro moiety results in increases in both melting point and mesophase range.     

Synthetic transformations and biological screening of benzoxazole derivatives: A review

The presence of benzoxazole moiety in most of the heterocyclic compounds is well reported. The present literature review mainly highlights the novel synthetic transformation and describes the biological potential of most of the heterocyclic compounds by virtue of presence of benzoxazole framework. Most of the researchers have revealed that benzoxazole derivatives exhibit significant antibacterial, anti-inflammatory, antifungal, anticancer, analgesic, antiviral, anti-tubercular, and anthelmintic activities. Benzoxazole moieties also act as tyrosinase inhibitor and cholesterol ester transfer protein inhibitor. This literature review may provide an opportunity to the chemists to design new derivatives of benzoxazole that proved to be the successful agent in view of safety, effectiveness, and efficacy.     

Syntheses,electrochemical studies and crystal structures of new unsymmetrical tetrathiafulvalene carboxylate derivatives

A series of new unsymmetrical tetrathiafulvalene carboxylate derivatives ( 7‐11 ) were synthesized and characterized by NMR, MS, electrochemical studies and X‐ray crystal structural determination. Compound 8 showed obvious changes in redox peak potentials as the concentration of p‐toluenesulfonic acid changes.