Fluorescent carbon dots derived from lactose for assaying folic acid

The fluorescent carbon dots were successfully synthesized by simply heating the mixture of lactose and Na OH solution. The as-synthesized carbon dots had been systematically characterized by fluorescence, Fourier transform infrared(FTIR), high resolution transmission electron microscopy(HR-TEM) and ~(13)C NMR. Since the fluorescence of the carbon dots was efficiently quenched by folic acid, the carbon dots were employed as selective fluorescence probes for detecting folic acid, depending on the formation of hydrogen bond among the functional group of folic acid(–OH, –COOH and –NH_2) and –OH and –COOH of the carbon dots. Moreover, the decrease of fluorescence intensity was capable of detecting folic acid in a linear range of 6×10~(-5)–8×10~(-8) mol/L with a detection limit of 1.2×10~(-9)mol/L at a signal-to-noise ratio of 3, suggesting a promising assay for folic acid. Significantly, the practicability of this fluorescence probe to assay folic acid in human urine samples was further evaluated.     

Novel chiral dithioethers derived from l-tartaric acid

The synthesis of a new family of systematically modified chiral dithioethers to be used as ligands is described. Phenylthioether derivative 5 and fluorine-containing dithioether ligands 6–8 and 13–15 were prepared by direct reaction of phenylthiol and o-, m- or p-fluorophenylthiol with two different ditriflate derivatives based on the l-tartaric skeleton. The chiral ditriflate 12 containing a dioxolane moiety was reacted with ethane- and propanedithiol, producing cyclic dithioethers 16 and 17, respectively, in good yields (≈50%). The analogous ditriflate 4 with benzyl ether protecting groups, having a skeleton without restricted rotation, gave the thiolane 9 as the main product.     

New chiral selenium electrophiles derived from functionalized terpenes

A convenient method for the synthesis of optically active dialkyl diselenides derived from bicyclic terpenes functionalized with hydroxy, etheral, sulfide, and selenide groups is described. The diselenides were used for a synthesis of chiral electrophilic selenium reagents, then in the asymmetric selenenylation of styrene and selenocyclization with o-allylphenol. The influence of nonbonding selenium-heteroatom interactions in the generated organoselenium electrophiles on the stereoselectivity of an addition reaction has been investigated. Calculations by a DFT method on a B3LYP (6-311G (d)) level, confirmed the existence of nonbonded selenium-heteroatom interactions in the investigated systems.     

Anticancer and microbicide action of carbon quantum dots derived from microcrystalline cellulose: Hydrothermal versus infrared assisted techniques

Urgent requirement for medication from cancer diseases and different microbial infections is interestingly considered. Carbon quantum dots (CQDs) as environmentally friendly fluorescent carbon nano-functionalized materials are popularly considered for application in medical purposes. Herein, a comparative study is presented for the affinity of CQDs ingrained from microcrystalline cellulose (MCC) prepared under hydrothermal conditions (CQDs-HT) versus that prepared under infrared assisted technique (CQDs-IR) for acting as anticancer and antimicrobial laborers. The estimated size averages for the obtained CQDs-HT & CQDs-IR were 7.8 & 9.8 nm, respectively. CQDs-HT showed rationally higher anti-proliferative action against Hepatocellular Carcinoma (HepG2) compared to CQDs-IR. Treatment with 1000 μg/mL of CQDs-IR & CQDs-HT exhibited 78 & 90 % mortality percentage of cancer cells, respectively. The obtained CQDs showed excellent microbicide potentiality and the minimum inhibitory concentration (MIC) from the synthesized CQDs-TH and CQDs-IR was ranged in 100–350 µg/mL and 300–400 µg/mL against different pathogens including bacteria and fungi, respectively. As a conclusion, hydrothermal technique showed seniority over infrared assisted technique in nucleation of CQDs with higher anticancer and microbicidal activities.     

Reinvestigation of a polymer-supported chiral auxiliary derived from serine

Due to concerns over the reliability of the reported synthesis and application of a polymer-supported chiral auxiliary by our group, we have reinvestigated the preparation of the polymer. Analysis of the resin has now been carried out by MAS ¹³C NMR spectroscopy, and as a result we now withdraw our previous claim of success.     

Protonation behaviour of chiral tetradentate polypyridines derived from alpha-pinene

Detailed protonation experiments of the [5,6]-pinenebipyridine molecule and the unsubstituted [4,5]- and [5,6]-CHIRAGEN[0] ligands in various solvents indicate a variety of structures of the protonated species. UV-visible and NMR measurements (including (15)N chemical shifts) show the transition from trans to cis conformation of [5,6]-pinenebipyridine upon protonation. The [4,5]-CHIRAGEN[0] ligand, in which the protonation sites of the nitrogen atom donors are at opposite sides of the molecule, behave essentially like two independent bipyridine moieties; this behaviour was monitored by UV-visible, CD and NMR spectroscopy (including (15)N data). In the case of the [5,6]-CHIRAGEN[0], a pocket of donor atoms provides a chiral environment for two protons per ligand.     

Photoisomerizable chiral compounds derived from isosorbide and cinnamic acid

The syntheses of derivatives of isosorbide and cinnamic acid are described. These chiral compounds are photoisomerizable. The Z-isomers could also be obtained after irradiation of these E-isomeric cinnamic derivatives. The Z-isomers were found to have a much lower helical twisting power than the E-isomers. These compounds are very suitable for use in cholesteric colour filters for liquid crystal displays. This was investigated by functionalizing the E-isomeric derivatives with two acrylate groups. The reflection wavelength of cholesteric layers made with these diacrylates can be tuned by means of UV irradiation because the pitch of the cholesteric layer increases on isomerization to the Z-isomer. Subsequent photopolymerization results in cholesteric films with excellent thermal stability.     

Asymmetric synthesis with new chiral auxiliaries derived from isosorbide

Chiral aminoethers derived from carbohydrates have been used for asymmetric alkylation of phenylacetic amides giving diastereoisomeric excess up to 83%.     

Intrinsically fluorescent carbon dots with tunable emission derived from hydrothermal treatment of glucose in the presence of monopotassium phosphate

A facile method is developed to synthesize intrinsically fluorescent carbon dots by hydrothermal treatment of glucose in the presence of monopotassium phosphate. The fluorescence emission of the carbon dots thus produced is tunable by simply adjusting the concentration of monopotassium phosphate.     

New class of P-stereogenic chiral Brønsted acid catalysts derived from chiral phosphinamides

A new class of NH Brønsted acid organocatalysts that feature P-stereogenic chirality was developed. These catalysts were prepared from P-stereogenic chiral phosphinamides and show similar reactivity to BINOL derived phosphoric acid toward the reduction of quinolines via transfer hydrogenation. It shows that stereoselectivity is induced by the P-chiral environment that is created by the substituents attached to the phosphorous atom, which can be readily tuned and modified.     

Asymmetric electrophilic amination of various carbon nucleophiles with enantiomerically pure chiral N-h oxaziridines derived from camphor and fenchone

The first two stable enantiomerically pure chiral N-H oxaziridines, derived from camphor and fenchone, are shown to act as electrophilic sources of nitrogen upon reaction with various carbon nucleophiles. Nitrogen is transferred, together with the camphor/fenchone unit, when deprotonated esters, malonates, and nitriles are used as nucleophiles. One of the ester or nitrile units in the substrate usually undergoes hydrolysis; a cyclic mechanism is proposed to account for this observation.     

New chiral auxiliary: Optically active thiol derived from camphor

A new camphor based mercapto chiral auxiliary has been prepared, and demonstrated to induce very high chiral inductions in the diastereoselective reductions of -sulfinylketones, in the presence of bivalent Lewis acids.     

Synthesis and thermal behavior of chiral oligomers derived from cholesterol

Synthesis and thermal properties of a series of Schiff base oligomers derived from naturally occurring cholesterol are described. In particular, four of them show smectic A and/or chiral nematic phase/s or an unknown mesophase, while the other is non-mesomorphic. Molecular packing in the SmA phase has been determined by the HRXRD experiment.     

Novel chiral pyrrolidinone scaffolds derived from threonine with antibacterial activity

The synthesis of chiral pyrrolidinones derived from threonine, making use of a Dieckmann or aldol ring closure, is described. Compounds were found to exhibit antibacterial activity, for which the correlation with various physiochemical parameters was examined. This chiral tetramate scaffold may provide a useful template for fragment-based drug design providing rapid access to novel antibacterial compound libraries.     

A chiral auxiliary derived from levoglucosenone in asymmetric Diels-Alder transformations

The Diels-Alder reaction of the acrylate derived from levoglucosenone with cyclopentadiene was studied under several conditions, in the presence and absence of a Lewis acid. The results showed satisfactory diastereomeric excess and the ratio of cycloadducts was found to depend on the reaction conditions. A reversal in stereoselectivity was observed when EtAlCl₂ or Et₂AlCl were employed as Lewis acids.     

Photoluminescent carbon nitride films grown by vapor transport of carbon nitride powders

The thermal vapor transport of nitrogen-rich carbon nitride powders produces carbon nitride films on substrates that retain significant nitrogen content, have conjugated bond character, and show blue photoluminescent emission near 450 nm.     

Tunable light emission from carbon dots by controlling surface defects

Carbon dots (CDs) are metal-free fluorescent materials that can be used in optical and electronic devices, but few studies have focused on one-step synthesis routes for CDs with tunable color and high photoluminescence quantum yield (PLQY). Herein, CDs with tunable light emission were synthesized using a novel amide-assisted solvothermal approach. The as-prepared CDs were well dispersed and homogeneous, with average diameters of approximately 2.0–4.0 nm, depending on the dopants. Owing to the surface states with different ratios of nitrogen- and oxygen-related species, different CDs can exhibit blue, green, red, or white emission with relatively high PLQYs of 61.6%, 41.3%, 29.1% and 19.7%, respectively. XPS measurements, in conjunction with DFT calculations, indicate that nitrogen substitution (pyridinic/pyrrolic nitrogen) dominates the blue emission, while introducing oxygen functional groups lowered the LUMO energy level, which resulted in redder emission. In addition, the CDs are demonstrated as a bioimaging probe in both in vitro and in vivo assays, and the white light CDs have been demonstrated to be potential fluorescent materials for white-light-emitting diode (WLED).     

Biological applications of carbon dots

Carbon dots (C-dots), since their first discovery in 2004 by Scrivens et al. during purification of single-walled carbon nanotubes, have gradually become a rising star in the fluorescent nanoparticles family, due to their strong fluorescence, resistance to photobleaching, low toxicity, along with their abundant and inexpensive nature. In the past decade, the procedures for preparing C-dots have become increasingly versatile and facile, and their applications are being extended to a growing number of fields. In this review, we focused on introducing the biological applications of C-dots, hoping to expedite their translation to the clinic.     

Highly enantioselective carbonyl reduction with borane catalyzed by chiral spiroborate esters derived from chiral 1,2-aminoalcohols

Novel spiroborate esters derived from nonracemic 1,2-amino alcohols were examined as chiral catalysts in the borane reduction of acetophenone and other aromatic ketones at room temperature. The optically active alcohols were obtained in excellent chemical yields and enantioselectivities up to 99% ee with 10% of catalyst.