Synthesis of silica-pillared layered lanthanum titanate with high thermal stability

It is now well established that layered solids other than smectite clays may bepillared to form three-dimensional crosslinked materials, the porosity of which isultimately tunable by the nature of the host substrate and the chemical species     

Synthesis and resolution of new paramagnetic α-amino acids

New, paramagnetic unnatural α-amino acids were synthesized by the O'Donnell method. In the new amino acids nitroxide is condensed with thiophene, benzene, and tetrahydroisoquinoline ring, or linked through a methylene, benzyl or propargyl spacer. Some of the racemic paramagnetic α-amino acid esters described earlier or in this work were resolved by fractional crystallization of diastereomeric salts. Another approach for optically active paramagnetic amino acids is the modification of S-tyrosine derivatives with Pd-catalyzed cross-coupling reactions with paramagnetic acetylene and with a paramagnetic boronic acid.     

Synthesis of leucine-enkephalin analogs containing α-amino squaric acid

Novel Leu-enkephalin analogs 10a-c in which the Tyr¹, Gly², or Gly³ residue of Leu-enkephalin 9 was replaced with α-amino squaric acid analog Sq-Tyr 8b or Sq-Gly 8a were synthesized starting from 14 or 18. Conformational analysis of 10a-c together with its model compound 26 and their opioid receptor binding activity were evaluated.     

Synthesis and thermal stability of a novel phosphorus-nitrogen containing intumescent flame retardant

A novel phosphorus-nitrogen containing intumescent flame retardant （P-N IFR） was prepared via the reaction of dichlor-opentate with N-methylaniline. The structure of the product was confirmed by ^1H NMR, ^31p NMR, MS and IR. TGA analysis showed it has effective thermal stability.     

Synthesis and study of new indoline spiropyran and its derivative with α-lipoic acid exhibiting low cytotoxicity

Russian Chemical Bulletin - New indoline spiropyran was synthesized by the cyclocondensation of 5-chlorine-substituted Fischer base with 2,7-dihydroxy-1-naphthaldehyde. This spiropyran was used to...     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Synthesis, characterization and antitumor activity of novel N-substituted α-amino acids containing ferrocenyl pyrazole-moiety

A series of new N-[(3-ferrocenyl-1-phenylpyrazol-4-yl)methyl] α-amino acids were prepared and characterized by a range of spectroscopic techniques and cyclic voltammetry. The in vitro antitumor activity of all synthesized compounds was investigated against cervix adenocarcinoma HeLa, melanoma Fem-x and myelogenous leukemia K562 cell lines using the MTT method. Tryptophan derivative 1l exhibited the highest cytotoxic activity in the cell growth inhibition of all three types of cell lines.     

Synthesis and reactions of α-fluoro-α-amino amides

N-((S)-1-Phenylethyl)halofluoroethanamides have been investigated as precursors to N-protected α-fluoro-α-amino amides by nucleophilic displacement of halide with nitrogen nucleophiles such as potassium phthalimide, sodium succinimide, sodium glutarimide, trimethylamine and sodium azide. With single diastereoisomers of the iodofluoroethanamide, clean inversion of configuration occurs at room temperature, but subsequent epimerisation may occur as a result of the liberated iodide. The α-fluoro-α-amino amides made underwent a wide variety of reactions depending on conditions, but in many cases the carbon-fluorine bond was compromised. However, reacting trimethylamine and N-((S)-1-phenylethyl)iodofluoroethanamide gave the corresponding α-fluorobetaine amide, and subsequent acidic hydrolysis led to α-fluorobetaine as the first example of an ‘unprotected’ α-fluoroamino acid.     

Negishi cross-coupling reactions of α-amino acid-derived organozinc reagents and aromatic bromides

The Negishi cross-coupling reaction of organozinc iodides derived from α-amino acids with aromatic bromides to give substituted phenylalanine derivatives is described, using either Pd(OAc)₂ or Pd₂(dba)₃ in combination with P(o-Tol)₃ as catalyst in DMF at 50 °C. Similar results are obtained using Pd[P^tBu₃]₂ as catalyst. The difference in reactivity displayed between aryl iodides and bromides (ArI>ArBr) has been utilised in a short synthesis of an unsymmetrical, orthogonally protected para-phenylene bis-alanine derivative.     

Synthesis of aromatic substituted B ← N embedded units with good stability and strong electron-affinity

Two chemically stable B ← N embedded units were synthesized, namely, BNIDT-Ph and BNIDT-Th, with aromatic phenyl (Ph) or thiophene (Th) groups, respectively, attached to the four coordination boron (B) atom. Single crystal data revealed that BNIDT-Ph and BNIDT-Th show obvious π-π interactions (3.83 vs. 3.79 Å) and B ← N dipole-dipole interactions (6.51 vs. 6.67 Å). BNIDT-Ph and BNIDT-Th exhibit strong electronic affinities of 3.70 and 3.81 eV, respectively. Fluorescence quenching was found between PBDB-T and the B ← N embedded molecules in solution, indicating exciton dissociation. These B ← N embedded molecules are potentially useful to further construct novel n-type semiconductors.     

Synthesis of new dialkyl α-aminophosphonates and dialkyl α-aminothiophosphonates

New dialkyl α-aminophosphonates and α-aminothiophosphonates were synthesized by reactions of dialkyl phosphites orO,O-dialkyl thiophosphites withN-benzylidene 2-(vinyloxy)ethylamine orN-(4-fluorobenzylidene)-2-(vinyloxy)ethylamine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1815–1817, September, 1999.     

Synthesis and characterization of novel low band-gap polymers containing squaraine units

Novel conjugated polymers based on squaric acid having 2,5-Bis[(E)-N-alkylpyrrol-2-ylvinyl]-3-alkylthiophene(PVTVP) unit in the main chain were successfully synthesized in good yields through polycondensation reaction.Their molecular structures were characterized by FT-IR and ~1H NMR.They have good solubility in common organic solvents,good thermal stability by thermal gravimetric analysis and high molecular weights.Their optical properties were investigated by UV-vis absorption spectra in CH_2Cl_2 solution,the results indicated all these compounds showed broad and strong spectral responses from 200nm to 900nm, suggesting their potential for application as organic plastic solar cells.     

Synthesis and Characterization of Novel Biodegradable Polyamides Containing α-amino Acid

The polyamides were obtained from 1,6-hexanediamine and diacylchloride which incorporated α -amino acid residues through interfacial polycondensation. High molecular weight (η_inh = 1.05–1.18 dL/g) polymers were produced with high yields. The structure of polyamides was verified by FT-IR and ¹H NMR spectra. They showed a remarkable ability to develop high crystallinity with melting temperatures in the range 117–191°C and was stable up to 350°C under nitrogen. Two methods such as alkali hydrolysis (10% NaOH w/v, 80°C) and enzymatic hydrolysis were employed for assessing the susceptibility of these polyamides to degradation. A preliminary investigation of the 5-fluorouracil (5-FU) release characteristics of these polyamides showed that the release rate increased with increasing water absorption of the polymers.     

Synthesis and structure of wholly aromatic liquid–crystalline polyesters containing meta- and ortholinkages

Wholly aromatic main-chain rigid-chain polymers containing meta- and orthokink linkages were synthesized. The thermal property, liquid crystallinity, and crystalline structure were studied using DSC, polarized light microscopy, and wide-angle X-ray scattering. These polymers exhibited liquid crystallinity up to 50 mol % of meta- and orthokink linkages. The existence of liquid crystallinity in these polymers may be attributed to the adoption of cis conformation in kink units in these polymers because the energy penalty for doing so can be compensated by the formation of the liquid–crystalline phase. The crystallinity of the polymers was low, and the crystal structure was quite similar to that of the pure polymers (without kink units). This can be explained by that fact that the crystal region mainly consists of the nonkink units, and the kink units disrupt the crystallization of the polymers and form defects. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1242–1248, 2001     

Synthesis, structure, and antimicrobial activity of copper(II) chelates containing imidazole and condensation products of α-amino acids with salicylaldehyde and its derivatives

Salicylaldehyde, 5-bromo- and 5-nitrosalicylaldehydes, 2-hydroxynaphthalene-1-carbaldehyde, and 2,3-, 2,4-, and 2,5-dihydroxybenzaldehydes reacted with glycine, alanine, and phenylalanine in ethanol in the presence of imidazole (Im) and copper(II) acetate hydrate to give copper(II) chelates with the composition Cu(Im)(L) · nH₂O (H₂L is the condensation product of the above aldehydes with α-amino acids; n = 0–2). The structure of the complex Cu(Im)(L¹) [H₂L¹ = 2-(2-hydroxybenzylideneamino)acetic acid] was determined by X-ray analysis. The crystalline structure of [2-(2-hydroxybenzylideneamino)acetato](imidazole)copper is formed by polymeric chains of the Cu(Im)(L¹) molecules linked through bridging oxygen atoms in the carboxy groups of the Schiff base ligand. The coordination unit has a distorted tetragonal pyramid configuration, where the pyramid base is composed of the phenol and carboxy oxygen atoms, CH=N nitrogen atom in the ligand H₂L¹ and imidazole nitrogen atom. The oxygen atom in the carboxy group in the neighboring molecule occupies the apical position of the coordination pyramid. The other coordination compounds also have polynuclear structure with the Schiff base H₂L acting as doubly deprotonated tridentate O,N,O-ligand and bridging carboxy groups. Thermal decomposition of the complexes includes their dehydration (70–95°C), while complete thermal decomposition occurs at 360–530°C. The synthesized complexes showed selective antimicrobial activity in the concentration range from 75 to 300 μg/ml against a number of standard strains of Staphylococcus aureus and Escherichia coli.     

Structure–property relationships of novel fluorinated polycarbonate polyurethane films with high transparency and thermal stability

Research on Chemical Intermediates - Novel polycarbonate diol (PCDL) was synthesized using dimethyl carbonate, 1,5-pentanediol (1,5-PD), 1,6-hexanediol (1,6-HD) and 1,4-cyclohexanedimethanol...     

Synthesis,crystal structures and magnetic properties of two new nickel(II) complexes with α-amino acid Schiff base

Two nickel(II) complexes [Ni(napgly)(MeOH)] _n (1) and [Ni(napphe)(H₂O)₂(MeOH)] · H₂O (2), where the tridentate Schiff-base ligands H₂napgly and H₂napphe are condensed from 2-hydroxyl-1-naphthaldehyde with glycine and L-phenylalanine, respectively, were prepared and structurally characterized. In 1, two inversion-related Ni(II) ions were bridged by two O atoms from the phenolate groups of two napgly anions, forming a centrosymmetric dimeric unit which was further linked by carboxylate groups to give a two-dimensional network. Magnetic susceptibility studies performed on the complex revealed anti-ferromagnetic coupling between the metal centers. In 2, the crystal structures of the complex displayed a distorted octahedral coordination geometry in which the ONO-donor Schiff base was bonded to the metal. Intermolecular H-bonds linked the compound into a 2-D layer structure.     

Synthesis of new α-aminonitriles containing organosilicon groups via three component Strecker reactions

A three-component efficient procedure is described for the synthesis of α-aminonitriles containing bis(trimethylsilyl)ethenyl groups from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1), aromatic amines and trimethylsilyl cyanide (TMSCN). Reactions have been studied in the presence of various Lewis acids as catalysts or in ionic liquids under mild conditions. Compound (1) was obtained via Peterson olefination of terephthaldehyde with tris(trimethylsilyl)methyllithium, (Me₃Si)₃CLi, in THF at 0 °C.