Enantioselective fluorescent sensors for amino acid derivatives based on BINOL bearing benzoyl unit

The derivatives of BINOL, (S)-1 and (R)-1, and their analogues have been prepared and the structures of these compounds have been characterized by IR, MS, ¹H, and ¹³C NMR spectroscopy and elemental analysis. The enantioselective recognition of these receptors has been studied by fluorescence titration and ¹H NMR spectroscopy. The receptors exhibited different chiral recognition abilities toward some enantiomers of chiral materials and formed 1:1 complexes between host and guest. Receptor (S)-1 or (R)-1 exhibits excellent enantioselective fluorescent recognition abilities toward amino acid derivatives.     

Synthesis and fluorescence study of 3-aminoalkylamidonapthalimides

A new series of fluorescent 3-aminoalkylamidonapthalimides were synthesized starting form 1,8-naphthalic anhydride. The structure of these compounds was characterized by ¹H NMR, ¹³C NMR, IR and Mass spectral analysis. The solvent effect on ¹H and ¹³C NMR of these compounds was studied in CDCl₃, CDCl₃:DMSO-d₆ (7:3, v/v) and DMSO-d₆. NMR chemical shift of the ortho and para protons and meta carbons of naphthalene ring showed maximum variation on moving from CDCl₃ to DMSO-d₆. In CDCl₃ solvent naphthalene ring may exist in slightly puckered form while in DMSO-d₆ it attains maximum planar configuration. Fluorescent properties of the title compounds and their precursors were investigated in different solvents like chloroform, ethanol, acetonitrile, acetone, DMSO and water. 3-Aminoalkylamidonapthalimides exhibited improved fluorescence than their precursors. Cyclic amino derivatives yielded higher fluorescence quantum efficiency in protic solvents, ethanol and water. Acylic amino derivatives yielded high fluorescence quantum efficiency in chloroform solvent. The maximum fluorescence quantum yield up to 0.14 was found for butyl amine derivative in chloroform solvent. In general proton accepting nucleophilic solvents like acetone and DMSO quenched the fluorescence.     

Selenium-Containing π-Conjugated Compounds for Electronic Molecular Materials

Abstract

Novel selenium-containing π-conjugated compounds have been studied for the development of organic metals, superconductors, and field-effect-transistors. Methylenedithiotetraselenafulvalene (MDT-TSF) and its related electron donors are effectively synthesized by the recently developed synthetic method consisting of the one-pot formation of 1,3-diselenole-2-selones, the deprotection/realkylation procedure of the protected tetrachalcogenafulvalene-thiolate and -selenolate, and the ring closing reaction via trans-alkylation on sulfur or selenium atom. These new compounds serve as good electron donors for developing not only highly conducting charge-transfer salts (> 10 ³ S cm^?1) but also superconducting salts. Among six selenium-containing methylenedichalcogeno-tetrachalcogenafulvalenes, we found that four of them can produce superconducting salts, indicating that the present compounds are superior class of electron donors.

For the development of high-performance organic semiconductors for organic field effect transistor (OFET) devices, we focused our attention to selenophene-containing acene-type compounds, namely benzo[1,2-b:4,5-b′]diselenophene (BDS) derivatives hitherto unknown. A new synthetic method for BDS derivatives consisting of double heterocycle-formation on the central benzene ring has been established and has made it possible to synthesize a range of BDS derivatives. Among them, 2,6-diphenyl derivative (DPh-BDS) shows very high hole mobility of 0.17 cm ² /Vs, which is classified into the highest class of field-effect mobility of organic thin films.     

Microwave-assisted synthesis of 3-hydroxy-4-pyridinone/naphthalene conjugates. Structural characterization and selection of a fluorescent ion sensor

Two novel 3-hydroxy-4-pyridinone/naphthalene conjugates (L1 and L2) with different distances between the chelating and the fluorescent moieties were synthesized using conventional heating and microwave irradiation achieving a shorter reaction time. The structure of both compounds was confirmed by X-ray crystallography, revealing that these compounds were isolated as hydrochloride salts in dihydroxypyridinium forms. In solution and in the presence of a base, the tautomeric keto forms may be obtained as it was elucidated by NMR analysis. The dihydroxypyridinium form of L1 exhibits fluorescence at 450 nm, both in ACN and DMSO, whereas the corresponding keto form exhibits fluorescence at 365 nm. In contrast, the dihydroxypyridinium form of L2 only fluoresces in DMSO, exhibiting a band at 340 nm, while the keto form is non-fluorescent. These distinct fluorescent behaviors reveal that the tautomeric form in which the ligands are isolated and the distance between the chelating and fluorescent functions strongly influences their fluorescence properties. Ligand L1 exhibits better fluorescence properties and its fluorescence intensity is quenched in the presence of variable concentration of Cu²⁺, Zn²⁺, and Fe³⁺, thus making it suitable to be used as ion sensor.     

基于杯[4]芳烃和S-联萘酚的荧光传感器的合成及其对N-Boc保护谷氨酸阴离子的对应选择性识别性能研究

合成了一种基于杯[4]芳烃和S-联萘酚单元的新型手性大环受体4,并用荧光光谱和核磁氢谱研究了该受体与阴离子的键合性质。非线性曲线拟合结果表明受体4与N-Boc保护L-和D-谷氨酸阴离子都能通过多重氢键形成1:1的络合物,而且对N-Boc保护谷氨酸阴离子对映体显示了较好的对应选择性识别性能（Kass(L) / Kass(D) = 4.65）。不同的荧光响应表明受体4可以用作N-Boc保护谷氨酸阴离子的对应选择性的荧光化学传感器。     

Hg2+‐Induced In Situ Generated Radical Cation of (S)‐BINOL‐Based Polymer for Highly Enantioselective Recognition of Phenylalaninol

Phenylalaninol enantiomers are one of the most important chiral compounds due to its presence in biologically active molecules and pharmaceutical products. In this paper, a novel chiral fluorescence polymer sensor incorporating (S)‐BINOL and oligomeric aniline via a nucleophilic addition–elimination reaction is designed and synthesized. Polymer sensor exhibits “turn‐off” fluorescence quenching response upon the addition of Hg²⁺, and “turn‐on” moderate fluorescence enhancement behavior towards phenylalaninol enantiomers. Meanwhile, this kind of (S)‐BINOL‐based polymer sensor can exhibit highly selective enantioselective recognition response towards (L)‐phenylalaninol upon the addition of Hg²⁺ and the value of ef can reach as high as 5.4, which can be attributed to the formation of in situ generated radical cation arisen from oligomeric aniline moiety by Hg²⁺ induction.

     

Study of non-covalent interactions of luotonin A derivatives and the DNA minor groove as a first step in the study of their analytical potential as DNA probes

The interaction between DNA and several newly synthesized derivatives of the natural anticancer compound luotonin A has been studied. The results from our work reveal an effective and selective alkaloid/double-stranded DNA (ds-DNA) interaction. In the presence of increasing amounts of ds-DNA, a noticeable fluorescence quenching of the luotonin A derivatives under study was observed. However, this effect did not take place when single-stranded DNA (ss-DNA) was employed. The association constant alkaloids/ds-DNA was calculated by quantitation of such a quenching effect. The influence of other quenchers, namely Co²⁺ and Br⁻ on the native fluorescence of luotonin A and derivatives was also studied, and a remarkable quenching effect was observed for both ions. We have also investigated how by binding DNA the alkaloids could get protected from the external Co²⁺ and Br⁻ quenchers. The Stern–Volmer constants (K _SV) for Co²⁺ and Br⁻ quenching effect on the studied alkaloids were considerably reduced (10–50%) after incubation of the compounds in the presence of DNA with regard to the K _SV values in absence of DNA. An increase in the fluorescence anisotropy values of luotonins was also produced only in the presence of ds-DNA but not in the case of ss-DNA. To better characterize the nature of that interaction, viscosimetry assays and ethidium bromide displacement studies were conducted. With regard to DNA reference solutions, the viscosity of solutions containing DNA and luotonin A derivatives was reduced or not significantly increased. It was also observed that the studied compounds were unable to displace the intercalating agent ethidium bromide. All of these results, together with the obtained association constants values (K _ass = 2.2 × 10² – 1.3 × 10³), support that neither covalent nor intercalating interactions luotonin A derivatives/ds-DNA are produced, leading to the conclusion that these alkaloids bind ds-DNA through the minor groove. The specific changes in the fluorescence behavior of luotonin A and derivatives distinguishing between ss-DNA and ds-DNA binding, lead us to propose these compounds as attractive turn-off probes to detect DNA hybridization.     

The Michael-Type Addition Reaction: A Stereocontrolled Construction of a New Quaternary Chiral Center at C(2) of 2-(4-Hydroxybenzyl)cyclohexanone Derivatives

The Michael-type addition reaction was used as a convenient method for the stereocontrolled construction of a new quaternary C-center at position 2 of 2-substituted cyclohexanones (Scheme) with the aim to study the effect of an additional substituent at C(2) in a series of biologically active compounds bearing generally a 2-substituted cyclohexanone moiety. Thus, a new series of compounds consisting of a racemate (RS)- 12 and its enantiomers (S)- and (R)- 12 (ee ≥96% for both enantiomers) was obtained. The Michael adduct derivatives (S)-, (R)-, and (RS)- 12 were subjected to a biological screening using several non-related insect species.     

Synthesis and enantioselective fluorescent sensors for amino acid derivatives based on BINOL

Four novel derivatives of 1,1′-bi-2-naphthol have been prepared and the structures of these compounds characterised by IR, MS, ¹H and ¹³C NMR spectroscopy and elemental analysis. The enantioselective recognition of these sensors has been studied by fluorescence titration and ¹H NMR spectroscopy. The sensors exhibited different chiral recognition abilities towards N-Boc-protected amino acid anions and formed 1:1 complexes between the host and the guest. Sensors exhibit excellent enantioselective fluorescent recognition ability towards the amino acid derivatives.     

Enantioselective Fluorescent Sensors for N-Boc-Protected Amino Acid Anions Based on BINOL

The four novel derivatives of BINOL have been prepared and the structures of these compounds characterized by IR, MS, ¹H and ¹³C NMR spectroscopy and elemental analysis. The enantioselective recognition of these receptors has been studied by fluorescence titration and ¹H NMR spectroscopy. The receptors exhibited different chiral recognition abilities towards N‐Boc‐protected amino acid anions and formed 1:1 complexes between host and guest. Receptor s exhibit excellent enantioselective fluorescent recognition ability towards the amino acid derivatives.     

Supramolecular Functions Related to the Redox Activity of Transition Metals

Abstract

The combination of the properties of different subunits in a multicomponent system may give rise to a function which is defined supramolecular. The presence of transition metals in one or more subunits may induce inter-component processes related to their redox and electron transfer (eT) properties, which trigger the supramolecular function (SF). The following examples are considered: (1) a receptor for transition metals is covalently linked to a fluorescent fragment; following recognition, a metal-to-fluorophore eT process quenches the fluorescence. SF: fluorosensing. (2) an azacyclam macrocycle, hosting the Ni^II/Ni^III redox couple, is covalently linked to a photoactive fragment: the Ni^III state quenches the neighboring fluorophore through an eT mechanism, the Ni^II state does not. SF: redox switching of a fluorescent signal. (3) a Cu^II ion is coordinated by two 2,2′-bipyridine molecules, each bearing a cyclam subunit containing a nickel centre; when nickel is in the divalent state, an inorganic anion X^? (N₃ ^?,NCO^?,NCS^?) is bound to Cu^II; on oxidation, X^? moves to the Ni^III centre. SF: electrochemically triggered translocation of X^? from copper to nickel and vice versa.     

Direct Resolution of the Enantiomers of Betaxolol and Related Intermediates,and Its Application

An OJ-H chiral column has been used for direct resolution of the enantiomers of betaxolol and related intermediates in the preparation of (S)-betaxolol. The enantiomers can be excellently resolved (R _S > 2) within 9.4 min with high peak symmetry. The enantiomers of some acetylated intermediates, which cannot be resolved on an OD-H column, can also be resolved. The method is simple and suitable for routine determination of ee values in the preparation of (S)-betaxolol.

     

Two spectral QSPR models of porphyrin macromolecules for chelating heavy metals and different ligands released from industrial solvents: CH2Cl2, CHCl3 and toluene

ABSTRACT

Two simple and reliable correlations are introduced for the prediction of emission and absorption of porphyrins and their derivatives, i.e. metalloporphyrins and ligand coordinated metalloporphyrins. They can be used to sense the extracted precious metals. The proposed models require only simple structural parameters such as the number of carbon, metal and metal-free molecular fragments of desirable porphyrins or their derivatives. Since the proposed models depend on molecular structures of the desired compounds, they can be easily applied for complex molecular structures. Experimental data of 272 porphyrin derivatives were used to derive and test the novel models for the assessment of their emission (Em.) and absorption (Abs.) values in three solvents namely dichloromethane, toluene and chloroform. The values of the coefficients of determination (r ²) for the training set (183 compounds) in dichloromethane and three different test sets, corresponding to the three mentioned solvents, for the emission and absorption correlations were greater than 0.70. The calculated values of the root-mean-square error (RMSE) for the training sets of Em. and Abs. correlations were equal to 7.56 and 4.86 nm, respectively. Further statistical parameters also confirm the high reliability of the new models.     

Synthesis of new chiral calix[4]azacrowns for enantiomeric recognition of carboxylic acids

Two novel chiral calix[4]azacrown ethers 4 and 5 bearing a furfuryl group on the nitrogen atom were developed by the reaction of dibromo- or ditosyl derivatives of p-tert-butylcalix[4]arenes 2 and 3 with a chiral diol, 1. The enantioselective recognition of these receptors towards the enantiomers of racemic carboxylic acids has been studied by ¹H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds 4 and 5 with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that both of the hosts form 1:1 instantaneous complexes with (R)- or (S)-mandelic acid and (l)- or (d)-dibenzoyltartaric acid. The receptors exhibited different chiral recognition abilities towards the enantiomers of racemic guests.     

Determination of R-(+)-higenamine enantiomer in Nelumbo nucifera by high-performance liquid chromatography with a fluorescent chiral tagging reagent

A sensitive method for determination of higenamine enantiomers based on a derivatization reaction with a fluorescent chiral tagging reagent, R-(−)/S-(+)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-Dimethylaminosulfonyl)-2,1,3-benzoxadiazole[R-(−)/S-(+)-DBD-PyNCS] has been developed. The tagging reagent preferably reacts with higenamine enantiomers under mild reaction conditions (at 60 °C for 60 min) in the presence of 3% pyridine to produce the corresponding fluorescent diastereomers with an excitation maximum at 450 nm and an emission maximum at 550 nm. The derivatives of higenamine enantiomers were efficiently resolved on a ODS column by an isocratic elution with water–acetonitrile–methanol mobile phase containing 0.2% formic acid. The resolution (Rs) values of the corresponding higenamine diastereomers was 1.52. The calibration curves of both R-(+)/S-(−)-higenamine enantiomers were linear over the concentration range of 0.2–400 μg/mL. The limits of detection (S/N = 3) per injection were 20 ng/mL. The developed method was applied successfully to the determination of higenamine in embryo of Nelumbo nucifera, a Chinese herbal medicine.     

Potentiometric,NMR, and Fluorescence‐Emission Studies on the Binding of Adenosine 5′‐Triphosphate (ATP) by Open‐Chain Polyamine Receptors Containing Naphthylmethyl and/or Anthrylmethyl Groups

The interaction in aqueous solution of adenosine 5′‐triphosphate (ATP) with a series of open‐chain polyamines linked at one or both ends to anthrylmethyl or naphthylmethyl fragments was followed by potentiometric titration, ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy, and by steady‐state fluorescence measurements. The results revealed greater stabilities for the compounds containing one anthracene moiety than for those with one naphthalene moiety, the stabilities of the compounds with both ends N‐substituted with naphthylmethyl groups being close to those containing just one anthrylmethyl unit. The ¹H‐NMR spectra showed that in all systems, there is involvement of π‐π stacking interactions in the stabilization of the adduct species. The competitive effect of the anions afforded by the supporting electrolyte was checked in some of the studied systems working at two different ionic strenghts (0.15M and 1.0M NaCl). The joint analysis of the spectrofluorimetric titrations and pH‐metric species‐distribution curves showed that for all the ATP? receptor systems, a quenching of the fluorescence occurred upon protonation of the adenine N(1)atom. Steady‐state fluorescence and time‐correlated single‐photon‐counting analysis of a system made up of ATP and a bis‐chromophoric polyamine receptor containing anthracene and naphthalene fluorophores established that the energy‐transfer process between the naphthalene and anthracene moieties is still operative despite the presence of ATP.     

Design and synthesis of fluorescent symmetric bis-triazolylated-1,4-dihydropyridines as potent antibreast cancer agents

Herein, we report the synthesis of fluorescent 1,4-dihydropyridine-linked bis-triazoles (2a–2n) through Hantzsch synthesis by the condensation of o/m-chloro-substituted benzaldehyde, ethyl 3-oxo-4(prop-2-yn-1-yloxy)butanoate, and ammonium acetate in the presence of Ba(NO₃)₂ as a catalyst followed by the click reaction of resultant Hantzsch product (1) with various aromatic as well as aliphatic azides. All the synthesized compounds were well characterized by ¹H-NMR, ¹³C-NMR, FTIR, and HRMS spectral techniques. Antibreast cancer evaluation of all the synthesized derivatives revealed that the compounds 2f (IC₅₀?=?7?±?0.02?µM) and 2g (IC₅₀?=?5?±?0.03?µM) showed better anticancer activity (lower IC₅₀) than the standard drug tamoxifen (IC₅₀?=?11.2?±?0.01?µM) against breast carcinoma (MDA-MB-231) cell line. The synthesized compounds were also screened against normal human embryonic kidney (HEK-293) cell line and found to be nontoxic. The fluorescent nature and cytotoxicity assay of these newly synthesized hybrids recommend their utility in tumor cell imaging.     

Tunable fluorescent sensing of cysteine and homocysteine by intramolecular charge transfer

An amphiphilic oligo p-phenylene derivative (DCHO) bearing electron-donating group (–NH(CH₂)₂OH) and electron-withdrawing group (–CHO) has been synthesised and characterised. The sensing characteristics of this probe (DCHO) for cysteine (Cys) and homocysteine (Hcy) are studied in a mixture solution of DMSO–HEPES by UV–vis and fluorescence spectra. ¹H NMR, MALDI-TOF and UV–vis titration experiments proved that thiazolidine and thiazinane derivatives were formed. The highly Cys/Hcy-selective fluorescence hypsochromic shift (>110 nm) can be observed due to the switching of intramolecular charge transfer, leading to potential fabrication of ratiometric fluorescent detection of Cys/Hcy.     

Natural terpene derivatives as new structural task‐specific ionic liquids to enhance the enantiorecognition of acidic enantiomers on teicoplanin‐based stationary phase by high‐performance liquid chromatography

We present the specific cooperative effect of a semisynthetic glycopeptide antibiotic teicoplanin and chiral ionic liquids containing the (1R ,2S ,5R )‐(–)‐menthol moiety on the chiral recognition of enantiomers of mandelic acid, vanilmandelic acid, and phenyllactic acid. Experiments were performed chromatographically on an Astec Chirobiotic T chiral stationary phase applying the mobile phase with the addition of the chiral ionic liquids. The stereoselective binding of enantiomers to teicoplanin in presence of new chiral ionic liquids were evaluated applying thermodynamic measurements and the docking simulations. Both the experimental and theoretical methods revealed that the chiral recognition of enantiomers in the presence of new chiral ionic liquids was enthalpy driven. The changes of the teicoplanin conformation occurring upon binding of the chiral ionic liquids are responsible for the differences in the standard changes in Gibbs energy (ΔG ⁰) values obtained for complexes formed by the R and S enantiomers and teicoplanin. Docking simulations revealed the steric adjustment between the chiral ionic liquids cyclohexane ring (chair conformation) and the β‐d ‐glucosamine ring of teicoplanin and additionally hydrophobic interactions between the decanoic aliphatic chain of teicoplanin and the alkyl group of the tested salts. The obtained terpene derivatives can be considered as “structural task‐specific ionic liquids” responsible for enhancing the chiral resolution in synergistic systems with two chiral selectors.