Aldehyde Functional Groups Research Articles

The formation of core cross-linked star polymer and nanogel assemblies facilitated by the formation of dynamic covalent imine bonds

Reversible addition-fragmentation chain transfer (RAFT) polymerization has been utilised to prepare diblock copolymer chains possessing ‘inert’ blocks of polystyrene and ‘reactive’ blocks displaying aldehyde or amino functional groups. These polymer chains were shown to cross-link through the formation of imine bonds in organic solvents to form kinetically stable polymer assemblies possessing core-cross-linked star (CCS) polymers architectures which display a size-dependency upon the concentration at which the cross-linking reactions are performed. Evidence was found for the formation of a 2-armed species as a side-product in the formation of CCS polymers. RAFT polymerization was utilised to prepare a series of methacrylate copolymers possessing only ‘reactive’ blocks displaying a significantly lower density of aldehyde and amino functional groups than the diblock copolymers utilized in the formation of CCS polymers. These copolymers were shown to cross-link through the formation of imine bonds in organic solvents to form polymer assemblies possessing nanogel architectures. The lower density of functional groups was required to promote the formation of discrete nanogel assemblies. This cross-linking also displayed a size-dependency upon the concentration at which the cross-linking reactions are performed. Macroscopic gelation of these polymer chains was observed at higher concentrations of the copolymer chains. Both the CCS polymers and nanogels underwent structural reconfiguration to linear polymer chains through component exchange facilitated by trans-imination with a small molecule amine. We speculate that the formation of both the CCS polymers and nanogels is under kinetic control on account of the lack of reversibility of imine bonds in organic solvents.

Enhanced Mucoadhesive Capacity of Novel Co-polymers for Oral Protein Delivery

Graft co-polymer networks have shown promise as devices for oral delivery of proteins. By increasing adhesion of these networks at the delivery site of the upper small intestine by utilizing small covalent chemical linkages caused by the addition of an aldehyde functional group we can make them more viable. These aldehydes bind covalently by way of a condensation reaction with the amines of the amino acids found in the glycoprotein network of the mucus layer of the small intestine to form imines. To investigate the effectiveness of this linkage the co-polymers are prepared in three different percentages of poly(ethylene glycol) (PEG) and aldehyde-modified PEG, and characterized through swelling, release and adhesion testing. The percentages of aldehyde-modified PEG used are 0.06, 0.6 and 3.3%. The swelling results indicate that the formulations with the aldehyde-modified PEG maintained the same pH sensitivity and transition around a pH of 5.8 as those formulations without the aldehyde moiety. Release results indicate that the release of insulin of the most promising 3.3% aldehyde formulation was successful with a release of about 80% after 3 h, which compares favorably with the similar release of the controls done in previous work. Adhesion testing was carried out through the use of a mechanical testing apparatus. Data have been gathered and plotted to give a detachment force (N) versus displacement (m) curve, of which the work of adhesion (μJ) was found by taking the area underneath the curve. Adhesion results indicate an increase to the already present adhesion of the co-polymers due to increased percentages of the aldehyde-modified PEG tethers where the 3.3% formulation showed an increase of 10–30 μJ over both control formulations.

An Injectable Oxidated Hyaluronic Acid/Adipic Acid Dihydrazide Hydrogel as a Vitreous Substitute

Vitrectomy is a common procedure for treating ocular-related diseases. The surgery involves removing the vitreous humor from the center of the eye, and vitreous substitutes are needed to replace the vitreous humor after vitrectomy. In the present study, we developed a colorless, transparent and injectable hydrogel with appropriate refractive index as a vitreous substitute. The hydrogel is formed by oxidated hyaluronic acid (oxi-HA) cross-linked with adipic acid dihydrazide (ADH). Hyaluronic acid (HA) was oxidized by sodium periodate to create aldehyde functional groups, which could be cross-linked by ADH. The refractive index of this hydrogel ranged between 1.3420 and 1.3442, which is quite similar to human vitreous humor (1.3345). The degradation tests demonstrated that the hydrogel could maintain the gel matrix over 35 days, depending on the ADH concentration. In addition, the cytotoxicity was evaluated on retina pigmented epithelium (RPE) cells cultivated following the ISO standard (tests for in vitro cytotoxicity), and the hydrogel was found to be non-toxic. In a preliminary animal study, the oxi-HA/ADH hydrogel was injected into the vitreous cavity of rabbit eyes. The evaluations of slit-lamp observation, intraocular pressure, cornea thickness and histological examination showed no significant abnormal biological reactions for 3 weeks. This study suggests that the injectable oxi-HA/ADH hydrogel should be a potential vitreous substitute.

ChemInform Abstract: Anodic Coupling Reactions and the Synthesis of C‐Glycosides.

AbstractBoth furanose and pyranose derivatives containing a masked aldehyde functional group can be prepared by the anodic coupling reaction between an electron‐rich olefin and an alcohol.

Large-Area Nanopatterning of Self-Assembled Monolayers of Alkanethiolates by Interferometric Lithography

We demonstrate that interferometric lithography provides a fast, simple approach to the production of patterns in self-assembled monolayers (SAMs) with high resolution over square centimeter areas. As a proof of principle, two-beam interference patterns, formed using light from a frequency-doubled argon ion laser (244 nm), were used to pattern methyl-terminated SAMs on gold, facilitating the introduction of hydroxyl-terminated adsorbates and yielding patterns of surface free energy with a pitch of ca. 200 nm. The photopatterning of SAMs on Pd has been demonstrated for the first time, with interferometric exposure yielding patterns of surface free energy with similar features sizes to those obtained on gold. Gold nanostructures were formed by exposing SAMs to UV interference patterns and then immersing the samples in an ethanolic solution of mercaptoethylamine, which etched the metal substrate in exposed areas while unoxidized thiols acted as a resist and protected the metal from dissolution. Macroscopically extended gold nanowires were fabricated using single exposures and arrays of 66 nm gold dots at 180 nm centers were formed using orthogonal exposures in a fast, simple process. Exposure of oligo(ethylene glycol)-terminated SAMs to UV light caused photodegradation of the protein-resistant tail groups in a substrate-independent process. In contrast to many protein patterning methods, which utilize multiple steps to control surface binding, this single step process introduced aldehyde functional groups to the SAM surface at exposures as low as 0.3 J cm(-2), significantly less than the exposure required for oxidation of the thiol headgroup. Although interferometric methods rely upon a continuous gradient of exposure, it was possible to fabricate well-defined protein nanostructures by the introduction of aldehyde groups and removal of protein resistance in nanoscopic regions. Macroscopically extended, nanostructured assemblies of streptavidin were formed. Retention of functionality in the patterned materials was demonstrated by binding of biotinylated proteins.

Highly Chemo‐ and Regioselective Reduction of Aromatic Nitro Compounds Catalyzed by Recyclable Copper(II) as well as Cobalt(II) Phthalocyanines

AbstractCopper/cobalt phthalocyanines were established for the first time as catalysts for the very efficient chemo‐ and regioselective reduction of aromatic nitro compounds to generate the corresponding amines. The selective reduction of nitro compounds was observed in the presence of a large range of functional groups such as aldehyde, keto, acid, amide, ester, halogen, lactone, nitrile and heterocyclic functional groups. Furthermore, the present method was found to be highly regioselective towards the reduction of aromatic dinitro compounds in a short time with high yields. In most of the cases the conversion and selectivity were >99% as monitored by GC‐MS. The reduction mechanism was elucidated by UV‐vis and electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry.

Anodic Coupling Reactions and the Synthesis of C-Glycosides

A convenient, two-step procedure has been developed for converting sugar derivatives into C-glycosides containing a masked aldehyde functional group. The chemistry takes advantage of an anodic coupling reaction between an electron-rich olefin and an alcohol. The sequence works for the formation of both furanose and pyranose derivatives if less polarized vinyl sulfide derived radical cation intermediates are used. With more polarized enol ether derived radical cations, the cyclizations work best for the formation of furanose derivatives where the rate of five-membered ring formation precludes elimination reactions triggered by the radical cation.

One-Stage Ecological and Economical Pretreatment of Linen Fabrics

A sodium chlorite bath for scouring and bleaching of linen fabric by a one-step process is activated by glyoxal as an organic-reducing compound having two aldehyde functional groups. Such activator has been found to be effective in bringing about the progressive decomposition of sodium chlorite. The treatment was achieved under a variety of conditions, and the bleaching effect of sodium chlorite/glyoxal system was appraised by monitoring the treated samples for the degree of whiteness (WI), loss in fabric weight (LW), wettability (W), carbonyl (CO) content, carboxyl (COOH) content, percentage of sodium chlorite decomposed, and tensile strength (TS). The best conditions for concurrent desizing, scouring, and bleaching of linen fabric with excellent whiteness index and acceptable tenacity were found to be 60°C and at initial pH of 10.35, with aqueous solution containing 5g/L NaClO2 , glyoxal 6 mmol/L, and 2g/L wetting agent for 120 min using the material-to‐liquor ratio (M/L) 1:30. Tentative mechanisms were also reported to account for the bleaching action of NaClO2 /glyoxal system.

Chemoselective Bromodeboronation of Organotrifluoroborates Using Tetrabutylammonium Tribromide: Application in (Z)-Dibromoalkene Syntheses

Tetrabutylammonium tribromide (TBATB) has been found to be a unique bromodeboronation reagent for organotrifluoroborates. When compared to previously reported bromodeboronation methods, the mild and metal-free reaction conditions tolerate a wider range of functional groups. High regio- and chemoselectivity are observed in the presence of both unsaturated carbon-carbon bonds and aldehyde functional groups. An efficient synthetic route to (Z)-dibromoalkenes from terminal alkynes has been developed using the TBATB-mediated bromodeboronation as a key step.

7,11,15,28-Tetrakis[(2-formylphenoxy)methyl]-1,21,23,25-tetramethylresorcin[4]arene cavitand ethyl acetate clathrate at 173 K

The title compound, C68H56O16, was synthesized as a novel synthetic inter­mediate towards deeper and more elaborate resorcin[4]arene cavitands. The structure is the first reported example of a resorcin[4]arene cavitand bearing aromatic aldehyde functional groups at the extra-annular rim of the mol­ecule. The 2-formyl­phen­oxy residues are found to assume two different orientations above the mol­ecular cavity. One half of the resorcin[4]arene cavitand mol­ecule appears in the asymmetric unit; the complete resorcin[4]arene cavitand structure was generated across a mirror plane. In addition, a highly disordered ethyl acetate solvent mol­ecule is present within the mol­ecular cavity.

Synthesis and characterization of low‐molecular‐weight polyacrolein

AbstractAcrolein was polymerized in a polar solvent in the presence of terc‐ and sec‐butyl lithium as initiators. Using a low monomer to initiator molar ratio and 1‐h reaction time, cyclic structures were shown to be formed in the main chain of the resulting oligomers. The influence of different monomer to initiator molar ratios on molecular weight and on molecular weight distribution was investigated. Chain‐transfer reactions toward the monomer resulted in lower molecular weights and narrower polydispersions as [M]/[I] increased. The influence of initiator type on the polymer molecular weight was also evaluated. FTIR analysis of the degradation products at different heating temperatures indicated that the oligomers structure is composed of aldehyde, ether, and vinyl functional groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Biodiesel production from sunflower, soybean, and waste cooking oils by transesterification using lipase immobilized onto a novel microporous polymer

This study aims at carrying out lipase-catalyzed synthesis of fatty acid methyl esters (biodiesel) from various vegetable oils using lipase immobilized onto a novel microporous polymeric matrix (MPPM) as a low-cost biocatalyst. The research is focused on three aspects of the process: (a) MPPM synthesis (monolithic, bead, and powder forms), (b) microporous polymeric biocatalyst (MPPB) preparation by immobilization of lipase onto MPPM, and (c) biodiesel production by MPPB. Experimental planning of each step of the study was separately carried out in accordance with design of experiment (DoE) based on Taguchi methodology. Microporous polymeric matrix (MPPM) containing aldehyde functional group was synthesized by polyHIPE technique using styrene, divinylbenzene, and polyglutaraldehyde. Thermomyces lanuginosus lipase was covalently attached onto MPPM with 80%, 85%, and 89% immobilization efficiencies using bead, powder, and monolithic forms, respectively. Immobilized enzymes were successfully used for the production of biodiesel using sunflower, soybean, and waste cooking oils. It was shown that immobilized enzymes retain their activities during 10 repeated batch reactions at 25 °C, each lasting 24 h. Since the developed novel method is simple yet effective, it could have a potential to be used industrially for the production of chemicals requiring immobilized lipases.

Microwave Effects on Chemical Functionalization of Hydrogen-Terminated Porous Silicon Nanostructures

This article reports on the chemical functionalization of hydrogen-terminated porous silicon (PSi−H) nanostructures with alkenes, aldehydes, and alkyl halides under microwave irradiation. The technique allows for the introduction of different functional groups on the surface. The use of microwave irradiation has a net effect on the hydrosilylation reaction rate. However, no specific microwave effect was observed when the freshly prepared PSi−H surface was modified with an alkene bearing an aldehyde function. The reaction takes place at both the carbon−carbon and the carbon−oxygen double bonds. The polar aldehyde functional group did not show a dominant effect in directing the reaction selectively at the carbonyl group.

Optimization of a Biomimetic Transamination Reaction

For a range of protein substrates, N-terminal transamination offers a convenient way to install a reactive ketone or aldehyde functional group at a single location. We report herein the effects of the identity of N-terminal residues on the product distribution generated upon reaction with pyridoxal 5'-phosphate (PLP). This study was accomplished through the combination of solid-phase peptide synthesis with detailed liquid chromatography-mass spectrometry analysis. Many N-terminal amino acids provided high yields of the desired transaminated products, but some residues (His, Trp, Lys, and Pro) generated adducts with PLP itself. N-terminal Cys and Ser residues were observed to undergo beta-elimination in addition to transamination, and the transamination product of N-terminal Gln was resistant to subsequent oxime formation attempts. The information generated through the screening of peptide substrates was successfully applied to a protein target, changing an initially unreactive terminus into one that could be modified in high (70%) yield. Thus, these studies have increased our predictive power for the reaction, both in terms of improving conversion and suppressing reaction byproducts. An initial set of guidelines that may be used to increase the applicability of this reaction to specific proteins of interest is provided.

A One-pot Synthesis of Novel Functionalized (E)-β-Arylvinyl Bromides from anti-2,3-Dibromo-3-(4-carboxyphenyl)propanoic Acid

A facile one-pot synthesis of functionalized (E)-β -arylvinyl bromides bearing various 4-alkoxycarbonyl and 4-aryloxycarbonyl groups was achieved by debrominative decarboxylation of anti-2,3- dibromo-3-(4-carboxyphenyl)propanoic acid in the presence of AgOAc and subsequent esterification in the presence of dicyclohexyl carbodiimide and dimethylaminopyridine. This method gives (E)-β - arylvinyl bromides in high stereoselectivities and high yields, and tolerates aldehyde, ester, and nitro functional groups.

Genome-free Viral Capsids as Carriers for Positron Emission Tomography Radiolabels

We have developed a modular synthetic strategy to append imaging agents to a viral capsid. The hollow protein shell of bacteriophage MS2 (mtMS2) was labeled on its inside surface with [18F]fluorobenzaldehyde through a multistep bioconjugation strategy. An aldehyde functional group was first attached to interior tyrosine residues through a diazonium coupling reaction. The aldehyde was further elaborated to an alkoxyamine functional group, which was then condensed with n.c.a. [18F]fluorobenzaldehyde. Biodistribution of the radioactive MS2 conjugates was subsequently evaluated in Sprague-Dawley rats. Relative to fluorobenzaldehyde, fluorine-18-labeled MS2 exhibited prolonged blood circulation time and a significantly altered excretion profile. It was also observed that additional small molecule cargo installed inside the capsids did not alter the biodistribution. These studies provide further insight into the pharmacokinetic behavior of nanomaterials and serve as a platform for the future development of targeted imaging and therapeutic agents based on mtMS2.

Photochemical Functionalization of Polymer Surfaces for Microfabricated Devices

Herein we report the topochemical modification of polymer surfaces with perfluorinated aromatic azides. The aryl azides, which have quaternary amine or aldehyde functional groups, were linked to the surface of the polymer by UV irradiation. The polymer substrates used in this study were cyclic olefin copolymer and poly(methyl methacrylate). These substrates were characterized before and after modification using reflection-absorption infrared spectroscopy, sessile water contact angle measurements, and X-ray photoelectron spectroscopy. Analysis of the surface confirmed the presence of aromatic groups with aldehyde or quaternary amine functionality. Enzyme immobilization and patterning onto polymer surfaces were studied using confocal microscopy. Enzymatic digests of protein were carried out on modified probes manufactured from thermoplastic substrates, and the resulting peptide analysis was completed using matrix-assisted laser desorption/ionization mass spectrometry. The use of functionalized perfluorinated aromatic azides allows the surface chemistry of thermoplastics to be tailored for specific lab-on-a-chip applications.

Protein functionalized micro hydrogel features for cell–surface interaction

Cross-linked hydrogel features have been patterned using subtractive lift-off of polymerized hydrogel film. Projection lithography and oxygen plasma etch was used to pattern parylene C polymer film. Molecular self-assembly of polymerizable monolayer was obtained in solution-phase and acrylamide based hydrogel was polymerized using free-radical polymerization on this substrate. Parylene C film was mechanically lifted-off to remove the blanket hydrogel film and micro hydrogel features (muhf) were obtained attached to the predefined patterns in the range from 1 to 60 mum. The muhf were functionalized with aldehyde functional groups, and proteins were coupled to them using Schiff base chemistry followed by reductive amination. Interaction of mesenchymal stem cells with transforming growth factor-beta 1 (TGF-beta1) functionalized muhf was studied, and TGF-beta1 was found to retain its tumor suppression activity.

Ring-Opening Reactions of Epoxides Catalyzed by Molybdenum(VI) ­Dichloride Dioxide

Transformation of epoxides to β-alkoxy alcohols, acetonides, and α-alkoxy ketones is achieved by using molybdenum(VI) dichloride dioxide (MoO2Cl2) as a catalyst. Alcohol, aldehyde, oxime, tosyl, and tert-butyldimethylsilyl functional groups are tolerated during the methanolysis and acetonidation of the functionalized epoxides. No polymerization product is observed with any of the epoxides. Direct conversion of epoxides devoid of sensitive functional groups into the corresponding α-methoxy ketone is achieved in a single step by using the MoO2Cl2/Oxone system.

Experimental and Computational Characterization of the 17O Quadrupole Coupling and Magnetic Shielding Tensors for p-Nitrobenzaldehyde and Formaldehyde

We have used solid-state 17O NMR experiments to determine the 17O quadrupole coupling (QC) tensor and chemical shift (CS) tensor for the carbonyl oxygen in p-nitro-[1-(17)O]benzaldehyde. Analyses of solid-state 17O NMR spectra obtained at 11.75 and 21.15 T under both magic-angle spinning (MAS) and stationary conditions yield the magnitude and relative orientation of these two tensors: CQ = 10.7 +/- 0.2 MHz, etaQ = 0.45 +/- 0.10, delta11 = 1050 +/- 10, delta22 = 620 +/- 10, delta33 = -35 +/- 10, alpha = 90 +/- 10, beta = 90 +/- 2, gamma = 90 +/- 10 degrees. The principal component of the 17O CS tensor with the most shielding, delta33, is perpendicular to the H-C=O plane, and the tensor component with the least shielding, delta11, lies along the C=O bond. For the 17O QC tensor, the largest (chi(zz)) and smallest (chi(xx)) components are both in the H-C=O plane being perpendicular and parallel to the C=O bond, respectively. This study represents the first time that these two fundamental 17O NMR tensors have been simultaneously determined for the carbonyl oxygen of an aldehyde functional group by solid-state 17O NMR. The reported experimental solid-state 17O NMR results provide the first set of reliable data to allow evaluation of the effect of electron correlation on individual CS tensor components. We found that the electron correlation effect exhibits significant influence on 17O chemical shielding in directions within the H-C=O plane. We have also carefully re-examined the existing experimental data on the 17O spin-rotation tensor for formaldehyde and proposed a new set of best "experimental" 17O chemical shielding tensor components: sigma11 = -1139 +/- 80, sigma22 = -533 +/- 80, sigma33 = 431 +/- 5, and sigma(iso) = -414 +/- 60 ppm. Using this new set of data, we have evaluated the accuracy of quantum chemical calculations of the 17O CS tensors for formaldehyde at the Hartree-Fock (HF), density-functional theory (DFT), Møller-Plesset second-order perturbation (MP2), and coupled-cluster singles and doubles (CCSD) levels of theory. The conclusion is that, while results from HF and DFT tend to underestimate the electron correlation effect, the MP2 method overestimates its contribution. The CCSD results are in good agreement with the experimental data.