Determination of primary amines by means of fluorescent schiff base derivatives

The formation of Schiff bases from the reaction of primary amines and several aromatic aldehydes has been studied. In many cases the Schiff bases were too unstable or feebly-fluorescent to be of analytical value. 1-Pyrenealdehyde and 2-fluorenealdehyde, however, were found to be suitable fluorigenic reagents for primary aliphatic amines, forming Schiff bases that were very stable and intensely fluorescent in acidic ethanol. The derivatives of 1-pyrenealdehyde could be detected at concentrations less than 1 ng ml^-1 in pure solution. Derivatives of 1-pyrenealdehyde could be readily produced by reactions at the surface of a t.l.c. plate. Combination of this approach with a simple deproteinizing procedure permitted analysis for nanograna quantities of primary amines in blood serum.     

CuCl-catalyzed aerobic oxidative reaction of primary aromatic amines

The oxidations of primary aromatic amines were investigated. Cuprous chloride-air system can catalyze the oxidation of primary aromatic amines to azo derivatives, anils, and/or quinone anils. The experimental procedure is simple and the products could be easily isolated in high yields.     

Manganese oxide-catalyzed transformation of primary amines to primary amides through the sequence of oxidative dehydrogenation and successive hydration

Manganese oxide octahedral molecular sieves (OMS-2) could act as an efficient, reusable heterogeneous catalyst for transformation of various primary amines to the corresponding primary amides through the sequence of oxidative dehydrogenation and successive hydration.     

A continuous-flow synthesis of primary amides from hydrolysis of nitriles using hydrogen peroxide as oxidant

A continuous-flow synthesis of primary amides from hydrolysis of nitriles using hydrogen peroxide as oxidant has been developed. Using this procedure, a variety of nitriles could be smoothly transformed into the desired primary amides in good to excellent yields. The mild reaction conditions and the flowing reaction system greatly improved the safety and make the reaction easy to scale up.     

Chemistry of N-Boc-N-tert-butylthiomethyl-protected alpha-aminoorganostannanes: diastereoselective synthesis of primary beta-amino alcohols from alpha-aminoorganostannanes

Reaction of N-Boc-N-tert-butylthiomethyl-protected alpha-aminoorganostannanes with n-BuLi generates the corresponding alpha-aminoorganolithiums. Reactions of these organolithiums with aromatic aldehydes provides N-protected beta-amino alcohols with diastereoselectivities up to >99:1 anti/syn; with aliphatic aldehydes, diastereoselectivities were typically 1:1. Diastereoselectivities varied depending on the amount of aldehyde used. The N-protected beta-amino alcohols could be deprotected to primary amines by treatment with NaH to generate oxazolidinones followed by basic hydrolysis. Alternatively, treatment of the protected amino alcohols with acid furnished cyclic acetals that could be deprotected to primary amines with BF(3).OEt(2) and HS(CH(2))(3)SH. Transmetalation of enantiomerically enriched organostannanes with n-BuLi at -95 degrees C provided organolithiums that, although less configurationally stable than N-Boc-N-methyl-protected alpha-aminoorganolithiums, could be trapped with aldehydes with near-complete retention of configuration.     

Sequential oxidation/asymmetric aldol reaction of primary alcohols by resin-supported catalysts

The sequential reaction including alcohol oxidation by TEMPO/Cu system and the asymmetric aldol reaction by peptide catalysis was realized using resin-supported catalysts. The step of oxidizing primary alcohols to the corresponding aldehydes could be dramatically enhanced through the introduction of triglycyl peptide to supported TEMPO and the method of pre-adsorbing a Cu-complex into resin beads.     

Copper-catalyzed rearrangement of oximes into primary amides

The atom-efficient and cost-effective rearrangement of oximes into primary amides is catalyzed by simple copper salts. The use of homogeneous Cu(OAc)₂ (1-2 mol %) was found to be effective for this transformation at 80 °C. The reaction was successful with either conventional or microwave heating. CuO and CuO/ZnO on activated carbon provided a competent reuseable heterogeneous catalyst which could be used in a batch process or in flow. Copper salts are much cheaper than the precious metals previously used for this rearrangement, and the reaction conditions are milder than those reported.     

Hydrosiloxane-Ti(OiPr)4: an efficient system for the reduction of primary amides into primary amines as their hydrochloride salts

A simple and useful method for the reduction of primary amides into the corresponding amines using a polymethylhydrosiloxane (PMHS)-Ti(OiPr)₄ reducing system is described. Aromatic as well as aliphatic primary amides are reduced in high selectivity and excellent yields. The reduction could proceed via dehydration of the primary amide group into the corresponding nitrile which is then reduced into the corresponding primary amine.     

Aerobic oxidative transformation of primary azides to nitriles by ruthenium hydroxide catalyst

In the presence of an easily prepared supported ruthenium hydroxide catalyst, Ru(OH)(x)/Al(2)O(3), various kinds of structurally diverse primary azides including benzylic, allylic, and aliphatic ones could be converted into the corresponding nitriles in moderate to high yields (13 examples, 65-94% yields). The gram-scale (1 g) transformation of benzyl azide efficiently proceeded to give benzonitrile (0.7 g, 90% yield) without any decrease in the performance in comparison with the small-scale (0.5 mmol) transformation. The catalysis was truly heterogeneous, and the retrieved catalyst could be reused for the transformation of benzyl azide without an appreciable loss of its high performance. The present transformation of primary azides to nitriles likely proceeds via sequential reactions of imide formation, followed by dehydrogenation (β-elimination) to produce the corresponding nitriles. The Ru(OH)(x)/Al(2)O(3) catalyst could be further employed for synthesis of amides in water through the transformation of primary azides (benzylic and aliphatic ones) to nitriles, followed by sequent hydration of the nitriles formed. Additionally, direct one-pot synthesis from alkyl halides and TBAN(3) (TBA = tetra-n-butylammonium) could be realized with Ru(OH)(x)/Al(2)O(3), giving the corresponding nitriles in moderate to high yields (10 examples, 64-84% yields).     

Chemoselective oxidation of primary alcohols catalysed by Ce(III)-complex intercalated LDH using molecular oxygen at room temperature

Herein we describe the preparation of an efficient heterogeneous catalyst consisting of an anionic Ce(III)-complex immobilized Zn/Al-layered double hydroxide (LDH) and its use in the catalytic liquid phase oxidation of primary alcohols using molecular O(2) at room temperature. Various primary alcohols could be transformed to their corresponding aldehydes in good to excellent yields using the set of optimal conditions. The heterogeneous catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity.     

Interaction of primary amphipathic cell-penetrating peptides with phospholipid-supported monolayers

The mesoscopic organization adopted by two primary amphipathic peptides, P(beta) and P(alpha), in Langmuir-Blodgett (LB) films made of either the pure peptide or peptide-phospholipid mixtures was examined by atomic force microscopy. P(beta), a potent cell-penetrating peptide (CPP), and P(alpha) mainly differ by their conformational states, predominantly a beta-sheet for P(beta) and an alpha-helix for P(alpha), as determined by Fourier transform infrared spectroscopy. LB films of pure peptide, transferred significantly below their collapse pressure, were characterized by the presence of supramolecular structures, globular aggregates for P(beta) and filaments for P(alpha), inserted into the monomolecular film. In mixed peptide-phospholipid films, similar structures could be observed, as a function of the phospholipid headgroup and acyl chain saturation. They often coexisted with a liquid-expanded phase composed of miscible peptide-lipid. These data strongly suggest that primary amphipathic CPP and antimicrobial peptides may share, to some extent, common mechanisms of interaction with membranes.     

Controlling primary hepatocyte adhesion and spreading on protein-free polyelectrolyte multilayer films

The development of new methods for fabricating thin films that provide precise control of the three-dimensional topography and cell adhesion could lead to significant advances in the fields of tissue engineering and biosensors. This Communication describes the successful attachment and spreading of primary hepatocytes on polyelectrolyte multilayer (PEM) films without the use of adhesive proteins such as collagen or fibronectin. We demonstrate that the attachment and spreading of primary hepatocytes can be controlled using this layer-by-layer deposition of ionic polymers. In our study, we used synthetic polymers, namely poly(diallyldimethylammonium chloride) (PDAC) and sulfonated poly(styrene) (SPS) as the polycation and polyanion, respectively, to build the multilayers. Primary hepatocytes attached and spread preferentially on SPS surfaces over PDAC surfaces. SPS patterns were formed on PEM surfaces, either by microcontact printing of SPS onto PDAC surfaces or vice versa, to obtain patterns of primary hepatocytes. PEM is a useful technique for fabricating controlled co-cultures with specified cell-cell and cell-surface interactions on a protein-free environment, thus providing flexibility in designing cell-specific surfaces for tissue engineering applications.     

The uptake behaviors of kaempferol and quercetin through rat primary cultured cortical neurons

The objective of this study was to investigate whether kaempferol and quercetin could be transported into primary cultured cerebral neurons, to establish a practical HPLC method with UV detection for the two flavonols in the neurons, and to study the uptake and transport behaviors of them through the neurons. The present results showed that the level of kaempferol in the neurons increased linearly and then reached a plateau with incubation time at the high concentration of 10 microg/mL, but not at the other two concentrations of 1 and 0.1 microg/mL. However, the levels of quercetin in the neurons were not detected at the three incubating concentrations, and there was a new peak detected in the cell whose retention time was shorter (3.42 min) than that of quercetin (4.65 min). This phenomenon suggested that quercetin might be transported into the neurons and then metabolized quickly to some derivative. Kaempferol could be transported into the neurons in a concentration- and time-dependent manner when the neurons were incubated with the culture medium containing kaempferol at the high dose. There was an apparent correlation between the concentrations of kaempferol in the medium and in the cell, indicating that the uptake of kaempferol in the cell increased along with its dose (10 microg/mL). However, there was a negative correlation between the concentrations of quercetin in the medium and in the cell. The results suggested that kaempferol and quercetin were disposed by the neurons at different way, and this might be an important factor for their different effects on primary cultured cortical cells.     

First practical cross-alkylation of primary alcohols with a new and recyclable impregnated iridium on magnetite catalyst

A new impregnated iridium on magnetite catalyst has been prepared, characterized, used and recycled, up to ten times with practically the same activity, for the first practical cross-alkylation of primary alcohols. The catalyst showed a wide reaction scope, is easy to prepare and handle, and it could be removed from the reaction medium just by magnetic sequestering.     

Nitric oxide turn-on fluorescent probe based on deamination of aromatic primary monoamines

The stable, water-soluble, and nonfluorescent FA-OMe can sense nitric oxide (NO) and form the intensely fluorescent product dA-FA-OMe via reductive deamination of the aromatic primary amine. The reaction is accompanied by a notable increase of the fluorescent quantum yield from 1.5 to 88.8%. The deamination mechanism of FA-OMe with NO was proposed in this study. The turn-on fluorescence signals were performed by suppression of photoinduced electron transfer (PeT), which was demonstrated by density functional theory (DFT) calculations of the components forming FA-OMe and dA-FA-OMe. Furthermore, FA-OMe showed water solubility and good stability at physiological pHs. Moreover, the selectivity study indicated that FA-OMe had high specificity for NO over other reactive oxygen/nitrogen species. In an endogenously generated NO detection study, increasing the incubation time of FA-OMe with lipopolysaccharide (LPS) pretreated Raw 264.7 murine macrophages could cause an enhanced fluorescence intensity image. In addition, a diffusion/localization cell imaging study showed that FA-OMe could be trapped in Raw 264.7 cells. These cell imaging results demonstrated that FA-OMe could be used as a turn-on fluorescent sensor for the detection of endogenously generated NO.     

The use of sulfamic acid as a primary standard in nonaqueous titrimetry

A method has been developed for the standardization of a typical nonaqueous base lithium methoxide, with an inorganic primary standard, sulfamic acid. 'T'his acid was found to dissolve readily in four independant basic solvents, dimethyl formamide, ethylenediamine, n-butylamine and dimethyl sulfoxide. Sulfamic acid could be titrated in each of these solvents, by both visual and potentiometric means with lithium methoxide dissolved in benzene-methanol. No gels nor precipitates resulted in the course of the titrations and the accuracy of the method was comparable to that obtained using benzoic acid as the primary standard. Conductometric titrations were also performed using sulfamic acid dissolved in two systems, dimethyl formamide and glacial acetic acid. In the latter solvent it was possible to titrate sulfamic acid with perchloric acid in glacial acetic acid.     

Effective gene delivery into primary dendritic cells using synthesized PDMAEMA-iron oxide nanocubes

Dendritic cells (DCs) have been a target of vaccine delivery, gene therapy, and cancer immunotherapy. However, gene delivery to primary DCs using traditional non-viral molecules has been a difficult challenge. Herein we have developed a gene delivery system to primary DCs using magnetic iron oxide nanocubes (MCs) coated with cationic polymer under the induction of a magnetic field. The MCs were coated with positively charged polymer, poly(2-dimethylamino) ethyl methacrylate (MCs-PD) before the plasmid gene (pMAX-GFP) was adsorbed on their surfaces. Three different sizes (15, 40 and 90 nm) of MCs were synthesized, and subsequently, PDMAEMA was assembled onto the MC surfaces (MCs-PD). MCs-PD exhibited zeta potentials of +23 to +26 mV, and the obtained particles showed superparamagnetic character with saturation magnetization of 17–66 emu/g. The MCs-PD of 10–100 μg/mL showed low toxicity on bone marrow-derived dendritic cells (BMDCs) in MTT assay, and they were well taken up by BMDCs under a magnetic field. Moreover, the particles with small size exhibited the enhanced plasmid transfection efficiency without the activation of BMDCs. The MCs-PD could be a promising non-viral gene delivery system that helps to manipulate primary DCs in vitro, which will be beneficial for cell-based immunotherapy.     

Photoisomerization mechanism of 11-cis-locked artificial retinal chromophores: acceleration and primary photoproduct assignment

CASPT2//CASSCF/6-31G photochemical reaction path computations for two 4-cis-nona-2,4,6,8-tetraeniminium cation derivatives, with the 4-cis double bond embedded in a seven- and eight-member ring, are carried out to model the reactivity of the corresponding ring-locked retinal chromophores. The comparison of the excited state branches of the two reaction paths with that of the native chromophore, is used to unveil the factors responsible for the remarkably short (60 fs) excited state (S(1)) lifetime observed when an artificial rhodopsin containing an eight member ring-locked retinal is photoexcited. Indeed, it is shown that the strain imposed by the eight-member ring on the chromophore backbone leads to a dramatic change in the shape of the S(1) energy surface. Our models are also used to investigate the nature of the primary photoproducts observed in different artificial rhodopsins. It is seen that only the eight member ring-locked retinal model can access a shallow energy minimum on the ground state. This result implies that the primary, photorhodopsin-like, transient observed in artificial rhodopsins could correspond to a shallow excited state minimum. Similarly, the second, bathorhodopsin-like, transient species could be assigned to a ground state structure displaying a nearly all-trans conformation.     

Aerobic oxidative transformation of primary alcohols and amines to amides promoted by a hydroxyapatite-supported gold catalyst in water

In the presence of an easily prepared hydroxyapatite-supported gold catalyst, namely Au/HAP, various kinds of structurally diverse primary alcohols including benzylic and aliphatic ones, and amines involving aromatic and secondary ones could be converted into the corresponding amides in water with up to 99% yield. Meanwhile, on the basis of experimental observations and literatures, a plausible reaction pathway was described to elucidate the reaction mechanism.     

Enhanced stability and activity of temozolomide in primary glioblastoma multiforme cells with cucurbit[n]uril

Temozolomide (TMZ) is the primary chemotherapeutic agent for treatment of glioblastoma multiforme (GBM) yet it has a fast rate of degradation under physiological conditions to the 'active' MTIC, which has poor penetration of the blood-brain barrier and cellular absorption. Herein we have demonstrated binding of TMZ within the cavity of nano-container cucurbit[7]uril, resulting in a decreased rate of drug degradation. Prolonging the lifetime of the TMZ under physiological conditions through encapsulation dramatically improved the drug's activity against primary GBM cell lines as more TMZ could be absorbed by the cells before degradation. This work can potentially lead to increases in the drug's propensity for crossing the blood-brain barrier and absorption into the GBM cells, thereby increasing the efficacy of this chemotherapy.