The Synthesis of Amide Dendritic Gelators and its Self-assembly Behavior in MMA

Three kinds of amide dendritic gelators, G₁-C₁₂-G₁, G₂-C₁₂-G₂ and gelator-1, were synthesized, and their self-assemble behavior in methyl methacrylate (MMA) was firstly investigated. The structures of the amide dendritic gelators were confirmed by ¹H-NMR and Mass spectra (MS). The gelation ability of the amide dendritic gelators was researched through tube inversion experiment, the results of which showed that different structures led to quite different gelation ability, including gel-sol temperature and critical concentration to form a stable gel. SEM experiments showed that three kinds of gelator formed different gel morphologies in MMA, all of which were nanoscale gel. All the three amide dendritic gelators could not only form stable gel network at certain temperature with different concentrations in MMA, but also in each case, an optically transparent gel was formed, which indicated dendrimers in the MMA had a good compatibility.     

Hydrophobic energy estimation for giant vesicle formation by amphiphilic poly(methacrylic acid)-block-poly(alkyl methacrylate-random-mathacrylic acid) random block copolymers

The self-assembly induced by the photocontrolled/living radical polymerization mediated by 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl was performed for amphiphilic poly(methacrylic acid)-block-poly(alkyl methacrylate-random-methacrylic acid) containing ethyl, n-propyl, and n-butyl methacrylates in order to control the morphology based on the hydrophobic-hydrophilic balance. The morphology transformation from films to spherical vesicles via the transition was well-controlled by adjusting the ratio of the alkyl methacrylate unit to the methacrylic acid in the hydrophobic random copolymer block. The copolymers formed the respective morphologies at different ratios dependent on the alkyl chain length of the methacrylates; the ratio for the formation of the respective morphologies decreased as the alkyl chain length increased. The hydrophobic energy estimation of these copolymers demonstrated that the respective morphologies had definite hydrophobic energies independent of the alkyl chain length, indicating that the morphologies were determined only by the hydrophobic magnitude of the random copolymer block.     

Regio- and diastereoselective functionalization of (−)-cytisine

(−)-N-Benzyl cytisine has been stereoselectively substituted in moderate to high yields on its carbon 6 (Csp³ α to the pyridone nitrogen). The reaction involved the in situ trapping of the carbanion formed by reaction of lithium diisopropyl amide (LDA) and its reaction with electrophiles (alkyl, allyl, benzyl halides, non-enolizable aldehydes, and Weinreb amide). In the absence of an electrophile or with its addition after the formation of the carbanion, a dimeric structure was isolated (yield: 42%) resulting from the 1,4-addition of the carbanion on the pyridone ring of another cytisine molecule. Deprotection of the benzyl group (Olofson's reagent) allowed the formation of 6-substituted derivatives of the natural product, cytisine, a potent agonist of nicotinic receptors of subtype α₄β₂.     

Biodetergent IV. Monolayers of corynomycolic acids at the air-water interface

The effects of alkyl chain length and of differences in the length of the two alkyl chains on the formation of a monolayer of chemically synthesized corynomycolic acid (2-alkyl-3-hydroxy fatty acid) at the air-water interface were examined. Hydrophobic interactions between the two alkyl chains are required for the formation of a condensed film, which is most stable when the total number of carbon atoms in the two alkyl chains is 25 or more and the difference in their lengths is one. Syn-isomers form condensed films but usually not anti-isomers. However, films may also be formed by the anti-isomer when the alkyl chain at the carboxy group (the 2-position) is longer than the alkyl chain at the hydroxy group (the 3-position). That is, the contribution of anti-isomers to condensed film formation depends on the polar carboxy group which has greater involvement in this formation. The extrapolated area for the condensed film of corynomycolic acid was 40 Ų per molecule, thus confirming that both the carboxy and hydroxy groups are present on the water surface when a bipolar monolayer is formed.     

On the solvolysis kinetics of amidoesters derived from β-aminoalcohols

To better understand reactivity in such systems, fifteen amidoesters derived from β-aminoalcohols were solvolyzed at the ester group in mildly basic methanol-d₄. All trials showed pseudo-first-order kinetics by ¹H NMR. The rate constants are about 2 to 140-fold larger than those found with simple alkyl esters. The least bulky N-acyl groups generally sponsor the largest rate constants, and strongly so in two cases, but apparently not as a result of lesser steric crowding between the amide and ester groups. Rate constants are also greater for those amidoesters favoring an anti conformation at the amide linkage.     

A family of low-molecular-weight organogelators based on N,N-diacyl-l-lysine: effect of alkyl chains on their organogelation behaviour

A family of low-molecular-weight organogelators based on N^α,N^?-diacyl-l-lysine was synthesized by acylation of N^?-dodecyl-l-lysine with acyl chlorides through the one-pot synthetic procedure and their organogelation properties were examined. These compounds functioned as an organogelator; especially, l-lysine derivatives possessing the branched alkyl groups are a better organogelation property. The NMR and IR studies demonstrate that the organogelation occurred through hydrogen bonding interactions between the amide groups and between the carboxy groups.     

Enantioselective total synthesis and correction of the absolute configuration of megislactone

The title compound, one of the constituents from Iryanthera megistophylla, has been synthesized in enantiopure forms. The stereogenic centers at C-2 and C-3 were constructed by using a chiral auxiliary induced asymmetric aldolization and the C-4 was derived from the corresponding optically active lactates. The carbon-carbon double bond in the side chain was derived from a pure cis vinyl iodide using a Suzuki coupling with an alkyl borane formed in situ from the corresponding terminal alkene. A previously unknown (partial) cis to trans transformation of an isolated C-C double bond in a long alkyl chain was observed during the deprotection of TBS group with CAN. Somewhat unexpectedly, the otherwise undetectable co-presence of the trans isomer of the remote double bond in a long alkyl chain was clearly revealed in ¹H and ¹³C NMR in the presence of a lactone ring. The present work unambiguously shows that the absolute configuration of the natural compound is the antipode of the one originally reported. Some errors in the previous ¹H and ¹³C NMR signal assignments are also corrected.     

Reaction of carboxamide with Cu2Oisonitrile complex; formation of a new chelated copper(I) complex

Reaction of carboxamides with Cu₂O in the presence of t-butyl isocyanide gave new chelated copper(I) complexes, which probably are formed by the insertion of t-butyl isocyanide into the coppernitrogen bond of copper(I) amide isonitrile complexes, which were initially produced from the carboxamides and Cu₂Ot-butyl isocyanide complex. The same chelated copper(I) complexes were prepared more readily by the reaction of the corresponding N-trimethylsilyl-carboxamides with Cu₂Ot-butyl isocyanide complex. Reactions of the copper(I) complexes thus obtained with alkylating agents, such as alkyl halides, alkyl tosylates and triethyloxonium tetrafluoroborate, also were described.     

Column packings for high-performance liquid chromatography and positron annihilation lifetime spectroscopy

Positron annihilation measurements as a function of temperature and the length of bonded alkyl groups have been carried out on silica gel samples. Silica gel samples were bare and bonded with alkyl group from C1 up to C18. The diameters of pores were deduced from the lifetime of trapped ortho-positronium (o-Ps), and it was found that o-Ps lifetime provides reasonable information on the pore sizes for both bare and alkyl bonded silica gels.     

Microstructure of N,N′-bis(cetyldimethyl)-α,ω-propanediammonium dibromide micelle and its dynamics in solution studied by 1H NMR

The characteristics of N,N′-bis(cetyldimethyl)-α,ω-alkane (propane and butane) diammonium dibromide (16-3-16 and 16-4-16) aqueous solutions were studied by one- and two-dimensional ¹H nuclear magnetic resonance (NMR). The measurements of self-diffusion coefficient and inter-proton distance at 318 K suggest that 16-3-16 spherical micelles are formed in the dilute solution at a concentration of 0.26 mmol/l and the polar head groups of the surfactant are in a saw-toothed form staying at the surface of the micelle to overcome the strong electrostatic repulsion force. Relaxation measurements obviously show that the spacer chain is rigid in the surface layer of the hydrophobic micellar core, and the side alkyl chains of 16-3-16 are packed more tightly than those of 16-4-16 in the micellar core. The line-shape analysis of the methyl protons at the end of the side alkyl chain of 16-3-16 and 16-4-16 suggests that two possible momentary morphologies of their side alkyl chains are situated in the micelle, respectively.     

Super organogelator based on tetrathiafulvalene with four amide derivatives and its F4TCNQ charge-transfer complex

A new series of tetrathiafulvalene-based organogelators endowed with four hydrophobic chains incorporating amide groups was synthesised and characterised. The resulting transparent organogels were obtained with organic solvents such as cyclohexane, carbon tetrachloride and chlorobenzene. Additionally, the length of the alkyl chain influenced the gelation ability of organogels. Considering the results, we concluded that compounds were ‘super gelators’. Interestingly, the gelators reacted with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane to form charge-transfer (CT) complexes and binary organogels. ¹HNMR and FT-IR revealed that cooperation of hydrogen bonding, π–π and CT interactions was the main driving force for formation of the native and CT gels. The scanning electron microscopy images of native xerogels revealed characteristic gelation morphologies of three-dimensional cross-linking networks, whereas the morphologies of CT complex xerogels showed amorphous rod-like aggregates. X-ray powder diffraction studies suggested that both gelator and CT complex maintained lamellar molecular packing mode in organogel phase.     

Self-organization of amide dendrons and their dendronized macromolecules

A polymerizable methacryl unit was introduced at the focal moiety of the amide dendrons which have amide branches and alkyl periphery. Their dendronized polymers were also prepared by the radical polymerization of the methacryl units. The self-organization characteristics of dendrons and dendronized polymers were then investigated in both the organic and aqueous phases. The amide dendrons (1M and 2M) in which the focal carboxyl group was blocked with methacryl units did not form gel in organic media such as chloroform or THF, whereas amide dendrons with a free carboxyl group at the focal point form self-organized structures. In the aqueous phase, 1M and 2M formed spherical vesicular assemblies. The dendronized polymers with first and second generation dendrons, 1P and 2P, respectively, exhibited lamellar and columnar organization in toluene. In addition to hydrogen bonding between the dendritic amide branches and van der Waals interactions between the alkyl periphery, steric confinement of dendritic side groups along the polymer backbone played a key role in the packing process of the dendronized polymers. In aqueous phase, 1P and 2P showed spherical vesicular aggregates with persistent stability in the presence of Triton X-100.     

Low molecular weight organogelators derived from threefold symmetric tricarbamates

A group of new low molecular weight organogelators based on threefold symmetric tricarbamate were synthesized and characterized. The tricarbamates with long alkyl chains were able to gelate a wide range of polar and nonpolar organic solvents such as acetonitrile and cyclohexane, generally at concentrations lower than 20 g/L. The best organogel formation was obtained using a threefold symmetric tricarbamate in n-dodecane, in which a sufficiently transparent gel was formed at the critical gelation concentration 1 g/L. Intermolecular hydrogen bonding by the tricarbamate in a nonpolar solvent benzene-d₆ was indicated by ¹H NMR spectra. Its maximum UV absorption was 11 nm higher in chloroform than in n-dodecane, and this red shift indicated increased conjugation between the benzene core and the carbamate substituents, which confirmed a change in its conformation from nonpolar to polar solvent. The self-assembling behavior of the tricarbamate in dilute solutions was investigated by TEM. Fiber-like networks were observed in a large range of solution concentrations.     

Cyclopentanones—VIII : Stereochemistry of the lithium-liquid ammonia reduction of 2,3-dialkyl-4-hydroxy-2-cyclopentenones

2,3-Dialkyl-1,4-cyclopentanediols are obtained by lithium-liquidammonia-alcohol reduction of 2,3-dialkyl-4-hydroxy-2-cyclopentenones. The configuration of the diastereoisomers formed was proved by ¹H-NMR spectroscopy and by chemical evidence. In the most abundant isomer the alkyl groups are trans and each is in trans position to the vicinal hydroxyl function. In another diastereoisomer formed in substantial amount the alkyl groups have a cis orientation and are trans to the vicinal hydroxyl function. The ¹H-NMR parameters found are more useful generally for configurational assignments to synthetic and modified prostaglandins.     

Synthesis and Identification of Epoxy Derivatives of 5-Methylhexahydroisoindole-1,3-dione and Biological Evaluation

Cyclic imides belong to a well-known class of organic compounds with various biological activities, promoting a great interest in compounds with this functional group. Due to the structural complexity of some molecules and their spectra, it is necessary to use several spectrometric methods associated with auxiliary tools, such as the theoretical calculation for the structural elucidation of complex structures. In this work, the synthesis of epoxy derivatives of 5-methylhexahydroisoindole-1,3-diones was carried out in five steps. Diels–Alder reaction of isoprene and maleic anhydride followed by reaction with m-anisidine afforded the amide (2). Esterification of amide (2) with methanol in the presence of sulfuric acid provided the ester (3) that cyclized in situ to give imides 4 and 4-ent. Epoxidation of 4 and 4-ent with meta-chloroperbenzoic acid (MCPBA) afforded 5a and 5b. The diastereomers were separated by silica gel flash column chromatography, and their structures were determined by analyses of the spectrometric methods. Their structures were confirmed by matching the calculated ¹H and ¹³C NMR chemical shifts of (5a and 5b) with the experimental data of the diastereomers using MAE, CP3, and DP4 statistical analyses. Biological assays were carried out to evaluate the potential herbicide activity of the imides. Compounds 5a and 5b inhibited root growth of the weed Bidens pilosa by more than 70% at all the concentrations evaluated.     

Synthesis and bioactivity of α-galactosylceramide analogues bearing an aryl group within the fatty amide chain

We describe the synthesis and bioactivity of analogues of α-galactosylceramide (1) bearing a long-chain alkyl group substituted at the meta or para position of an aryl group embedded within the amide chain. We compared the ability of these compounds and of 1 and C6Ph (2, which has a phenyl group at the amide chain terminus) to stimulate murine invariant Natural Killer T cells and to dock with human CD1d.     

Effect of Solvent and Molecular Structure on the Enhanced Fluorescence and Supramolecular Chirality of Schiff Bases in Organogels

The structures and properties of some Schiff base compounds doped in organogels were investigated. It was found that although individual Schiff bases could not form organogels with organic solvents, they can gel by mixing with an organogelator, N,N′-bisoctadecyl-L-Boc-glutamic-diamide, which formed transparent organogels in dimethyl sulfoxide (DMSO) or toluene (Tol). The enhancement of doping Schiff bases fluorescence in the organogel was observed in comparison with that of the corresponding solution. Furthermore, in the DMSO organogel, the induced chirality was obtained from the doping Schiff base with long alkyl chain. In contrast, the Schiff bases without long alkyl chain could not form supramolecular chiral assemblies in organogel. It was suggested that through gel formation the chirality of the gelator could be transferred to the Schiff base through hydrophobic interaction among the long alkyl chains.     

Molecular motion of the main chain for a series of Poly(alkyl l-glutamate)s as studied by 2H NMR

²H NMR measurements were carried out for a series of poly(alkyl l-glutamate)s (PALG) in which the ¹H of the amide group in the main chain is replaced by ²H in order to investigate the mobility and motional mode of the main chain. At low temperature, the ²H spectra were typical powder patterns, which have three principal values. The temperature dependencies for the ²H NMR spectra varied with the side chain length. For PALG with a short side chain length, Δv₁, Δv₂, and Δv₃ are almost constant in all temperature ranges. As the side chain length increases, the difference between the peaks and shoulders decreased with temperature. For PG-12-N-D, the peaks and shoulders are fused at high temperature in a liquid crystalline state. The mobility and molecular motion of the main chain is discussed based on the obtained ²H NMR spectra.     

Antimicrobial agents as photostabilizers for rigid poly(vinyl chloride)

Some amide derivatives of ethylene glycol‐bis(2‐aminoethylether)‐N,N,N^′,N^′‐tetraacetic acid (EGTA) have been prepared via their coupling with different aniline derivatives: amino, methyl, chloro, and hydroxy aniline. The EGTA amide derivatives were characterized, and their antimicrobial activities were evaluated. These antimicrobial agents have been investigated as photostabilizers for rigid poly(vinyl chloride) (PVC), suspension PVC, with a K value of 70. Their stabilizing efficiencies were evaluated by determining the percentage of weight loss, the intrinsic viscosities, as well as the amount of formed gel of the photodegraded PVC. The extent of discoloration and the change in the mechanical properties of the photodegraded polymer were also evaluated. The applied materials reduced the loss in weight that resulted from HCl evolution during photodegradation. Both viscosity and gel content measurements showed also a decrease in their values during the degradation process. The decrease in the percentage of gel formation upon applying the investigated photostabilizers reflects the lowering in extent of cross‐linking of the polymer, which implies preserving the mechanical properties of PVC. The extent of discoloration was also improved in the presence of the investigated compounds. The results have proved a greater stabilizing efficiencies of the antimicrobial EGTA amide derivatives than that of the phenyl salicylate ultraviolet (UV) absorber, which is commonly used as an industrial stabilizer. A radical mechanism was proposed to account for the stabilizing action of the investigated products. Copyright © 2011 John Wiley & Sons, Ltd.     

Solution phase structures of enantiopure and racemic lithium N-benzyl-N-(α-methylbenzyl)amide in THF: low temperature 6Li and 15N NMR spectroscopic studies

The antipodes of lithium N-benzyl-N-(α-methylbenzyl)amide are highly efficient enantiopure ammonia equivalents for the asymmetric synthesis of β-amino acid derivatives via conjugate addition to α,β-unsaturated esters. ⁶Li and ¹⁵N NMR spectroscopic studies of doubly labelled ⁶lithium (S)-¹⁵N-benzyl-¹⁵N-(α-methylbenzyl)amide in THF at low temperature reveal the presence of lithium amide dimers as the only observable species. Either a monomeric or dimeric lithium amide reactive species can be accommodated within the transition state mnemonic for this class of conjugate addition reaction. This enantiopure lithium amide offers unique opportunities over achiral (e.g., lithium dibenzylamide) and C₂-symmetric (e.g., lithium bis-N,N-α-methylbenzylamide) counterparts for further mechanistic study owing to the ready distinction of the various dimers formed.