Micelle formation of polystyrene-<Emphasis Type="Italic">block</Emphasis>-poly(4-<Emphasis Type="Italic">tert</Emphasis>-butoxystyrene) in hexane

A new type of hexane-soluble polymeric surfactant based on poly(4-tert-butoxystyrene) (P ^t BSt) was prepared by the nitroxide-mediated living radical polymerization, and their self-assemblies in hexane were explored. Polystyrene-block-P ^t BSt diblock copolymers with six different P ^t BSt block lengths were obtained by the sequential living radical polymerization of styrene followed by 4-tert-butoxystyrene using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator; Mn(P ^t BSt block) = 13,500, 21,700, 26,600, 47,500, 91,300, and 108,000 at the constant length of the PSt block (Mn = 12,900). Dynamic light-scattering studies demonstrated that the copolymers self-assembled into monodispersed spherical micelles in hexane. The hydrodynamic diameter of the micelles increased with an increase in the P ^t BSt block length. The micellar size also increased as the copolymer concentration increased. However, the size decreased as a result of the increasing temperature due to a decrease in the aggregation number. The ¹H NMR analysis confirmed that the copolymers formed micelles with PSt cores.     

Effect of the structure of the biodegradable triblock polymer polylactide-<Emphasis Type="Italic">block</Emphasis>-(polycaprolactone-<Emphasis Type="Italic">stat</Emphasis>-polylactide)-<Emphasis Type="Italic">block</Emphasis>-polylactide on its mechanical properties

The effect of the structure of the triblock biodegradable polymer synthesized from ɛ-caprolactone and L-lactide via coordination ring-opening polymerization on its mechanical properties is studied. Effects of the structure of the triblock polymer on its relative elongation at break, elastic modulus, and shape recovery after unloading are estimated by the modeling method. It is shown that the properties of the polymer in relation to its structure can be predicted. The structure-dependent characteristics of the polymers are in following ranges: relative elongation at break, 7–1500%; elastic modulus, 1–330 MPa; and shape recovery, 0–95%. The modeling data are confirmed by the back synthesis of the polymers with optimized desired characteristics.     

Copolymer of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride with maleic acid as drug carrier

A copolymer of N,N-diallyl-N,N-dimethylammonium chloride with maleic acid of constant composition was prepared under the conditions of radical initiation. The possibility of the functionalization of the copolymer with drugs containing amino groups by polymer-analogous transformations was examined. Conditions were found for preparing conjugates of the copolymer with isoniazid. The structures and the quantitative compositions of the conjugates were determined by ¹³С NMR spectroscopy, and the possibility of preparing conjugates with controlled drug content was demonstrated.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Mono-<Emphasis Type="Italic">meso</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylporphyrin

Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield.     

Synthesis of amino acid conjugates of glycyrrhizic acid using <Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-dicyclohexylcarbodiimide

Synthesis of amino acid conjugates of glycyrrhizic acid with the use of N-hydroxyphthalimide, N,N'-dicyclohexylcarbodiimide, and tert-butyl esters of L-amino acids (valine, isoleucine, phenylalanine, and methionine) was performed followed by deprotection with trifluoroacetic acid. The target amino acid conjugates were isolated by column chromatography on silica gel in 40–45% yield. The structure of the prepared compounds was confirmed by IR and ¹³C NMR spectroscopy.     

Effect of molecular weight of poly-<Emphasis Type="Italic">N</Emphasis>-benzyl-<Emphasis Type="Italic">N,N</Emphasis>-dimethyl-<Emphasis Type="Italic">N</Emphasis>-methacryloyloxyethylammonium chloride on its complexation with sodium dodecyl sulfate

Complexation of a cationic polyelectrolyte, poly-N-benzyl-N,N-dimethyl-N-methacryloyloxyethylammonium chloride, with an ananionic surfactant, sodium dodecyl sulfate, in aqueous solutions is studied. The effect of the molecular weight of the polymer on phase separation in the system and on the stability, conformation, and surface activity of the polyelectrolyte-surfactant complexes is examined.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

Synthesis of <Emphasis Type="Italic">N,N</Emphasis>-disubstituted (<Emphasis Type="Italic">Z</Emphasis>)-<Emphasis Type="Italic">O</Emphasis>-methylnicotinamide oximes

A number of (Z)-N,N-dialkyl- and (Z)-N-acyl-N-alkyl-O-methylnicotinamide oximes was synthesized. Their configuration was confirmed by the NOESY experiment. Evaluation of fungicidal activity of compounds obtained was performed.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)-<Emphasis Type="Italic">N</Emphasis>-(3-alkoxy-4-acyloxyphenylmethylene)-<Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">e</Emphasis>-cyclohexyl)amines

Previously unknown E isomers of azomethines (Schiff bases) were synthesized from vanillal and vanillin esters by their reaction with cyclohexylamine.     

New flavonoid-<Emphasis Type="Italic">C</Emphasis>-glycosides from <Emphasis Type="Italic">Triticum aestivum</Emphasis>

Two new flavonoid-C-glycosides named triticuside A (1a) and triticuside B (1b) were isolated from bran of Triticum aestivum L. The structures of the two new compounds were elucidated by spectral techniques including ¹H NMR, ¹³C NMR as well as HSQC, HMBC, and COSY. Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 135–137, March–April, 2008.     

Mass-spectra and molecular structure of <Emphasis Type="Italic">O</Emphasis>-alkyl <Emphasis Type="Italic">N,N</Emphasis>-dialkylamidocyanophosphates

The electron impact mass spectra were recorded and the key directions of fragmentation of the highly toxic O-alkyl N,N-dialkylamidocyanophosphates were identified. The sets of characteristic ions for the 10 subgroups of the main group of this class were determined. Based on the values of the mass numbers and peak intensities of characteristic ions generalized spectral images for each of the 10 studied subgroups of this class were simulated. A new method of group identification of O-alkyl N,N-dialkylamidocyanophosphates was developed.     

Behavior of a Thermosensitive Star-Shaped Polymer with Polyethyloxazoline-<Emphasis Type="Italic">block</Emphasis>-Polyisopropyloxazoline Copolymer Arms

The aqueous solutions of the star-shaped eight-arm polymer in which arms consist of the block copolymer of poly(2-ethyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline) and a more hydrophilic poly(2- ethyl-2-oxazoline) is attached to the calix[8]arene core are studied by light scattering and turbidimetry. For the sake of comparison, the linear block copolymer modeling arms of the star-shaped polymer is examined. The temperature and concentration dependences of light scattering intensity and optical transmission, the hydrodynamic radii of particles occurring in solutions, and their fraction in solution are determined. At room temperature, solutions of the linear copolymer are molecularly dispersed because of a high hydrophilicity of blocks and aggregates are formed in solutions of the star-shaped polymer as a result of interaction between hydrophobic calix[8]arene cores. As the temperature grows, the dehydration of poly(2-isopropyl-2-oxazoline) units initially occurs and entails both the compaction and aggregation of star-shaped molecules. At higher temperatures, the dehydration of poly(2-ethyl-2-oxazoline) leading to phase separation begins. The temperature of phase separation grows upon dilution. A high intramolecular density of the star-shaped polymer is responsible for a marked deceleration of self-organization processes. This effect is especially pronounced in the vicinity of the phase-separation temperature.     

Synthesis of Novel <Emphasis Type="Italic">D</Emphasis>-<Emphasis Type="Italic">Seco</Emphasis>-Pregnenes

Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003 Published online September 25, 2003     

Molecular Cloning and Expression Analysis of an <Emphasis Type="Italic">Mn</Emphasis>-<Emphasis Type="Italic">SOD</Emphasis> Gene from <Emphasis Type="Italic">Nelumbo nucifera</Emphasis>

A rapid amplification cDNA end (RACE) assay was established to achieve the complete sequence of mitochondrial manganese-superoxide dismutase (Mn-SOD) cDNA in Nelumbo nucifera. The obtained full-length cDNA of Mn-SOD was 926 bp and contained a 699-bp open reading frame encoding an Mn-SOD precursor of 233 amino acids. The recombinant of Mn-SOD expressed by PET-32a vector in Escherichia coli BL21 was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blotting assays. A 3D structural model of the Mn-SOD was constructed by homology modeling. Real-time polymerase chain reaction analysis revealed that Mn-SOD mRNA was expressed in young leaves, blossom, stems, and terminal buds during reproductive stage but with the highest expression in young leaves. This significant difference demonstrated the differential expression of Mn-SOD in various organs of N. nucifera.     

Molecular structure of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">o</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzyl)cytisine

The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008.     

Secondary self-assembly behaviors of PEO-<Emphasis Type="Italic">b</Emphasis>-P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS triblock terpolymers in solution

A series of PEO₄₅-b-PtBA₅₃-b-PS _x (x = 42, 84, 165) triblock terpolymers were synthesized by the atom transfer radical polymerization and characterized by size exclusion chromatography and ¹H NMR. Their self-assemblies were conducted by a two-step hierarchical self-assembly method and a one-step dialysis method and the self-assembly behaviors were investigated. The morphologies, sizes, and size distributions of micelles produced by the self-assembly were determined by transmission electron microscopy and dynamic light scattering. The secondary self-assembled structure of PEO₄₅-b-PtBA₅₃-b-PS _x obtained by the two-step hierarchical self-assembly could be controlled by tuning the length of PS block, the core forming block. The micelles were uniform with diameters of 20–25 nm and their size distributions, except for that of PEO₄₅-b-PtBA₅₃-b-PS₁₆₅, were narrow with particle size distribution indexes ranging from 0.014 to 0.246. The one-step dialysis of the triblock terpolymers produced vesicular micelles with distinct vesicle walls that exhibited similar thicknesses. The vesicles did not show significant aggregation. The size distribution of PEO₄₅-b-PtBA₅₃-b-PS₄₂ vesicle was the narrowest with a particle size distribution index value of 0.135. The PEO₄₅-b-PtBA₅₃-b-PS₁₆₅ vesicles tended to overlap with each other.