Synthesis and theoretical study of first generation CCK-functional dendrimers

A convenient synthesis and theoretical study of five CCK-functional dendrimers is described.The dendritic cores were linked with the CCK(Trp-Met-Asp(OBn)-PheNH2) fragment by forming amide bonds to give five target molecules.The structures of CCK-functional dendrimers were characterized by NMR,MS spectrum and predicted using molecular mechanics and PM3 semi- empirical molecular orbital theory.     

Synthesis and characterization of nano-structured Th1?x Ce x O2 mixed oxide

GEL combustion technique was applied to obtain oxides of thorium and cerium from their respective nitrate solutions using citric acid as the gelating agent. The dried samples were characterized by IR and TG studies. Intermediate and final products during TG studies have been isolated and characterized by XRD studies. All the TG runs during heating of thorium and cerium nitrate with citric acid dried Gels showed a two step process. The weight loss at each step and the X-ray data of the product at each step, helped in suggesting a possible mechanism. Kinetic study was carried out independently for each step. The reaction mechanism as observed during interactive procedure was found to be diffusion controlled. The kinetic parameters (activation energy and pre-exponential factor) for each step in all reactions have been calculated. Observations from XRD studies show that with increase in cerium concentration in the oxides, the lattice parameter values have shown a decreasing trend for all the five compositions studied. It was observed that in TG studies with increase in cerium concentration, the final temperature of the reactions have shown a decreasing trend. SEM studies of the powders reveal that synthesized oxides have a tendency to form agglomerate of varying size ranging from 50 to 100 μm in case of mixed oxides but the size of thorium oxide powder so synthesized have pore size 10–100 μm. SEM images shows that GEL combustion may result in agglomeration, if the temperature is not properly controlled to the desired value. SEM studies also reveal that each agglomerate contains approximately 10–100 individual particles. Surface area of the mixed oxide powders were determined using Gas adsorption technique. The surface area was found to be in the range of 3–17 m²/g in all cases. Specific surface area of thorium oxide was found to be lesser than cerium oxide but in case of mixed oxides surface area decreases with increase in cerium content. Majority of pores, indicating the particle size are in the range of 0.01–0.04 cm³/g.     

Molecular geometry and conformation: mathematical relations between intra-molecular distances and conformation in Fréchet-type dendrimers and dendrons

A geometrical approach to two distances in Fréchet-type dendrimers is presented in this paper: the dependence on the conformation of the distance between the centres of two consecutive phenyls (i.e. the two phenyl rings of a benzyl-phenyl-ether motif), and the calculation of the radius of a G1 dendron (i.e. the distance between the C1 atom of the focal phenyl ring and the C4 atom of a phenyl ring superior to it), as a function of torsion angles. This approach enables determination of the extreme values of these distances.     

Synthesis and complexation of a ‘mixed’-pyridine-naphthalene homooxacalixarene

A deep-cavity ‘mixed’ octahomotetraoxacalix[2]naphthalene[2]pyridine macrocycle has been synthesised and its single-crystal X-ray structure has been determined. Molecular modeling studies suggested that this macrocycle could be an effective host for guest aromatic diol(s) similar to Wang's methylazacalixpyridines. Binding constants were determined using ¹H NMR chemical shifts changes and comparisons were made between the diols which were tested.     

Synthesis and characterization of dendronized poly(methylsiloxane) with appendent Fréchet-type dendrons

A new kind of dendronized poly(methylsiloxane) (3a and 3b) with appendent Fre-chet-type poly(aryl ether) dendrons has been synthesized and characterized by GPC, DSC, TGA, fluorescence and UV-Vis spectra.     

Synthesis and Crystal Structure of 2-（1-Naphthalenylamino）-4-thiazolidinone

The compound 2-(1-naphthalenylamino)-4-thiazolidinone was synthesized by the reaction of 1-(naphthalene-1-yl)thiourea with ethyl chloroacetate in an ionic liquid, and its structure was characterized by IR, 1H NMR and single-crystal X-ray diffraction. The crystal of the title compound belongs to monoclinic, space group P21 /c with a=10.0081(3), b=14.5312(4), c=7.8739(2) , β=99.425(3)°, Z=4, V=1129.64(5)3 , Dc=1.425 g/cm3 , μ=0.269 mm-1 , F(000)=504, the final R=0.0519 and wR=0.1507. X-ray analysis indicated that the five-membered ring is essentially planar in this molecule, and intermolecular hydrogen bonds N(1)-H(1)…N(2), C(3)-H(3)…O(1), C(4)-H(4)…O(1) and C(12)-H(12a)…O(1) were observed. π-π Stacking interactions contribute to the stability of the structure. DSC-TG analysis showed that the title compound experienced a phase change at 190 ℃ and began to decompose above 240 ℃.     

Synthesis and Crystal Structure of 2-Amino-1, 1-diferrocenylethanol

2-Aminoalcohols are useful intermediates in organic chemistry, for example, they serve for the synthesis of various heterocycles1, chelate complexes2, and for the ring expansion of cycloalkanones3. 2-Aminoalcohols containing ferrocene as bidentate ligand may be converted into multinuclear compounds. Several methods for the preparation of 2-aminoalcohols have been developed including reduction of the trimethylsilyl cyanohydrins4 or β-nitromethyl alcohols5 and treatment of the epoxides with a…     

Synthesis of 1-Benzoyl-3-aryl-4-hydroxy-4-phenylimidazolidin-2-thiones

l-Benzoyl-3-aryl-4-hydroxy-4-phenylimidazolidin-2-thiones can be synthesized readily from the cyclization of 1-benzoyl-3-arylthioureas with bromine-acetophenone in the presence of excess triethylamiqe.     

Synthesis of cyclodextrin–pyrrole conjugates possessing tuneable carbon linkers

Cyclodextrins are naturally occurring cyclic oligosaccharides consisting of glucose units. The main feature of cyclodextrins is the ability to accommodate various lipophilic compounds in their interior, which determines them to be popular helpers to the mankind. However, there is still a demand for new derivatives for advanced applications. Herein, we report the synthesis of β-cyclodextrin–pyrrole conjugates. Their preparation is based on an amide bond formation or copper(I)-catalysed azide-alkyne cycloaddition between β-cyclodextrin and pyrrole derivatives. The main advantage of the synthetic approach lies in the possibility to attach the substituent in β-position, because polypyrroles possessing a substituent in this position are generally more conductive than the N-substituted ones. Moreover, the presented synthetic route is general and allows tuning the properties (various types of connections and lengths) of a linker. The presented cyclodextrin–pyrrole derivatives thus open the door for new applications in the field of sensors or tissue engineering.     

Synthesis and Crystal Structure of 1-Methylsulfinyl-1-methylthio-2-cyano-2-phenylethylene

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The Synthesis of the 2- and 2′-Monodeoxygenated Analogues of β-Maltosyl-(1→4)-Trehalose 1

Abstract

Two derivatives of β-maltosyl-(1→4)-trehalose monodeoxygenated at C-2 or C-2′ have been synthesized in [2+2] block syntheses. N-Iodosuccinimide-mediated coupling of tetra-O-benzyl-glucose to tri-O-acetyl-D-glucal followed by O-acetylation furnished 3,4,6-tri-O-acetyl-2-deoxy-2-iodo-α-D-mannopyranosyl 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside (7), which was used as a starting material for both tetrasaccharides. For the preparation of the 2′-monodeoxygenated saccharide the deoxyiodo pyranose moiety of 7 was further elaborated by de-O-acetylation, O-benzylidenation, O-benzylation, and selective reductive opening of the benzylidene acetal to give glycosyl acceptor 10. Glycosylation with hepta-O-acetylmaltosyl bromide and deprotection including removal of the iodo substituent afforded the 2′-deoxymaltosyl-(1→4)-trehalose 14. On the other hand, the non-iodinated pyranose moiety of 7 was transformed to a glycosyl acceptor. The removal of the benzyl groups of 7 necessitated also the reduction of the iodo group at this early stage. The resulting 3,4,6-tri-O-acetyl-2-deoxy-α-D-arabino-hexopyranosyl α-D-glucopyranoside was subjected to a similar reaction sequence as above to finally result in the 2-deoxymaltosyl-(1→4)-trehalose 22.

     

Synthesis and Characterization of a Novel Compound SnDy2O4

In recent years, the research on rare earth became a focus, and a lot of rare earth complex compounds with AB2O4 stoichiometry were prepared1-3. The compound SnDy2O4 is expected to spinel-type phase while it exhibits a new structure type. SnDy2O4 was prepared by the thermal decomposition of the oxalate precursor that was prepared by rheological phase reaction method. SnO(AR), Dy2O3(99.9%) and H2C2O4·2H2O are ground in molar ratio 1:1:4.1, and placed into the reaction apparatus. …     

Synthesis and Crystal Structure of 2-Amino-I, 1-diferrocenylethanol

2-Amino-l,l-diferrocenylethanol 2 was prepared by reduction of trimethylsilylcyanohydrin ether of diferrocenyl ketone. The crystal structure of 2 was further defined by X-raydiffraction.     

Synthesis of ZrO2–SiO2 mixed oxide by alcohol-aqueous heating method

The preparation of ZrO₂–SiO₂ mixed oxide has been carried out simply by heating an alcohol-aqueous mixture. Preparation conditions such as volume ratio of alcohol to water and prehydrolysis time of tetraethoxysilane had more important effect on the homogeneity of mixed oxide. A self-catalytic effect on the resultant Zr–O–Si formation is observed. By employing FT-IR, XRD, NH₃-TPD and pyridine adsorption FT-IR techniques, the mixing homogeneity of the mixed oxides in terms of the amount of Zr–O–Si hetero-linkages has been investigated in detail. The results indicate that the amount of Zr–O–Si hetero-linkages increases with the increase of ZrO₂ content in mixed oxides. Moreover, the phase segregation and acidity generation of mixed oxides are studied and factors responsible for good mixing are also discussed. Using this approach, a series of highly homogeneous mixed oxides with ZrO₂ content of 20–70 mol% are obtained at the optimized preparation condition.     

Synthesis and characterization of the ZnxCd1−xIn2S4 pseudoternary solid solution

We have synthesized several compounds of the Zn_xCd_1−xIn₂S₄ family by solid phase reactions and chemical transport reactions using iodine. The reaction products have been characterized as to composition, structure, and lattice dynamics. Here we discuss and compare the different results obtained by the two synthesis methods.     

Synthesis and properties of thiazole halohydrazones. 1. Synthesis and interaction of 2-α-chlorobenzylidenehydrazino-4-ethoxycar-bonyl-thiazole with triethylamine in the presence of dipolarophiles

In the interaction of 2--chlorobenzylidenehydrazino-4-ethoxycarbonylthiazole with triethylamine, a nitrilimine is formed as an intermediate that does not react with dipolarophiles, but rather undergoes intramolecular 1, 5-dipolar cyclization to form 3-phenyl-5-ethoxycarbonylthiazolo[2,3-c]-1,2,4-ttiazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 253–255, February, 1994. Original article submitted November 30, 1993.     

Synthesis of conjugates of β-cyclodextrin with polyamidoamine dendrimers and their molecular inclusion interaction with levofloxacin lactate

Polyamidoamine (PAMAM) dendrimers of different generations (G2 and G4) conjugated with β-cyclodextrin (β-CD), PAMAM (G2, G4)-CD, were synthesized using substitution reaction from mono-6-iodine-β-cyclodextrin and PAMAM dendrimers. The resulting molecular structures were characterized by NMR, IR. The molecular interaction between various dendrimers and levofloxacin lactate (LFL) were investigated by monitoring the fluorescence of LFL in the presence of dendrimers in buffer solution (pH 7.4) at 25?°C. It was found that the PAMAM (G2, G4)-CD possesses higher sensitizing ability than that of the corresponding parent dendrimers and natural β-CD, and increases concomitantly with the increases of generation and content of β-CD, suggesting that the PAMAM (G2, G4)-CD possesses stronger inclusion ability with LFL. The possible interaction mechanism between PAMAM-CD and LFL was proposed by ¹H NMR analysis and theoretical calculation. The results show that the LFL molecule is located at the amine end of dendrimer molecule and along the side of cyclodextrin cavities to form supramolecular complexes. Furthermore, results indicate that the main driving force of the complex could be attributed to the electrostatic interactions and hydrogen bonding between LFL and PAMAM-CD, as well as the synergistic effect of intermolecular forces.