Side chain effect on the double helix formation of ethynylhelicene oligomers

Three series of ethynylhelicene oligomers with different side chains were synthesized: (P)-bD-n (n = 2-6) with branched alkyloxycarbonyl side chains; (P)-S-n (n = 2-7) with decylsulfanyl side chains; and (P)-DF-n (n = 4, 6, 8, 10) with alternating decyloxycarbonyl and perfluorooctyl side chains. The double helix formation of these side chain derivatives was compared to that of (P)-D-n with decyloxycarbonyl side chains. CD, UV-vis, and vapor pressure osmometry (VPO) studies showed that (P)-bD-n formed double helices as well as (P)-D-n. CD studies in trifluoromethylbenzene at different temperatures and concentrations indicated that the stability of the aggregate of (P)-bD-6 was similar to that of (P)-D-6. Bulkiness of side chains had little effect on aggregation, which indicated that π-π interactions of the aromatic moiety were essential for double helix formation. (P)-S-n were random coils in all solvents examined except in trifluoromethylbenzene. Whereas (P)-D-7 formed a double helix at 1 × 10(-3) M in toluene, (P)-S-7 was a random coil. This result indicated that the double helix forming ability of (P)-S-n was substantially lower than that of (P)-D-n. Based on the previous observation that (P)-F-n formed a more stable double helix than (P)-D-n, the order of stability may be summarized as follows: (P)-F-n > (P)-D-n and (P)-bD-n >(P)-S-n. The lower stability of (P)-S-n compared to that of (P)-F-n was ascribed to the softness and/or the electron-rich nature at the m-phenylene moiety. (P)-DF-n did not form a stable double helix. It was speculated that a regular alternating arrangement of soft/hard or electron-rich/deficient moieties is important for stable double helix formation. Side chains of ethynylhelicene oligomers can play significant roles in determining the stability of double helices.     

Two types of two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers

Two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers in toluene exhibited two different properties depending on difference in numbers of helicenes in the two components. The combinations (M)-5/(P)-4, (M)-6/(P)-4, and (M)-7/(P)-4, which contained oligomers with comparable numbers of helicenes, formed transparent gels (Type I gels). The combinations (M)-6/(P)-3, (M)-7/(P)-3, and (M)-8/(P)-3, which contained oligomers with considerably different numbers of helicenes, formed turbid gels (Type II gels). Negative Cotton effects were observed for the Type I gels in the region between 350 and 450 nm, and were positive for the Type II gels, despite the use of (M)-oligomers for the longer components. UV/vis exhibited absorption maxima at 350 nm for the Type I gels and at 338 nm for the Type II gels. Different behaviors in gel formation processes were observed by fluorescence studies. Atomic force microscopy analysis showed fiber structures of 25-50 nm diameter for Type I gels and bundles of 100-150 nm diameter for Type II gels. The stoichiometry in gel formation also differed: The Type I gels showed 1:1 stoichiometry of the two components; the Type II gels showed no 1:1 stoichiometry, likely 1:2 stoichiometry. Using the Type I and II gels, two-layer gel systems were constructed.     

Synthesis of macrocyclic imides by one-step ring enlargement

By one-step ring-enlargement reaction with isocyanates, 2-cyano- and 2-(ethoxycarbonyl)-substituted cycloalkanones are converted into macrocyclic imides.     

Synthesis and ring‐opening polymerization of macrocyclic aryl ketone oligomers

A series of macrocyclic aryl ketone oligomers were prepared by the reaction of phthaloyl dichloride or isophthaloyl dichloride with various bridge‐linking electron‐rich aromatic hydrocarbons 3a–d under pseudo‐high dilution conditions in the presence of Lewis base via Friedel–Crafts acylation reaction. Detailed structural characterization of these oligomers confirmed the cyclic nature by a combination of MALDI‐TOF‐MS, GPC, and ¹H NMR analyses. These cyclic ketone oligomers have high solubility in organic solvents and the cyclic oligomers derived from phthaloyl dichloride are amorphous. The cyclic ketone oligomers readily undergo anionic ring‐opening polymerization in the melt by using potassium 4,4′‐biphenoxide as the initiator, producing linear, high molecular weight poly(ether ketone)s. Moreover, the isothermal chemorheology of the ring‐opening polymerization of cyclic oligomers 4a and 4b was also investigated. The results show that the shear viscosity of the molten reactive mixture is lower than 10 Pa · S at a constant shear rate of 0.05 rad/sec and increases slowly in the initial stage of ring‐opening polymerization. Copyright © 2009 John Wiley & Sons, Ltd.     

含呋喃环Schiff碱型大环化合物的合成及其与Ba^2+,Sr^2+配合行为

利用Mn^2+，Ba^2+及Sr^2+作为模板离子，合成了一类新型的含呋喃环系 Schiff碱型大环化合物，如L^1和配合物L^2Ba(ClO4)2，L^3Ba(ClO4)2和L^4Ba (ClO4)2.L^2-L^4的Ba^2+配合物经与NaSO4水溶液反应解络，得到自由配体L^2， L^3和L^4，配体L^2和L^3分别与Sr^2+作用，得到配合物L^2Sr(ClO4)2和L^3Sr (ClO4)2。上述大环配体和各种配合物均经元素分析，IR，^1H NMR，MS等证实了它 们的结构和组成。     

Synthesis of macrocyclic ligands containing the indole ring system

2,7-Diformyl-3-methyl-4,6-dimethoxyindole (6) has been synthesized and converted by metal template reactions into the macrocyclic complexes (10–12).     

Twelve-, fourteen- and sixteen-membered macrocyclic ligands and a study of the effect of ring size on ligand field strength

Complexes of Cr^III and Ni^II with a macrocyclic tetradendate 12-, 14- and 16-membered nitrogen donor ligand were prepared and characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectra. The complexes are of the high-spin type. The effect of ring size on the Dq_(xy) value is also discussed and the field strength was found to have a maximum value for the 14-membered ring, when metal ion fits best into the cavity rather than when the metal ion is compressed by the macrocycle.     

Polycationic amphiphilic cyclodextrins as gene vectors: effect of the macrocyclic ring size on the DNA complexing and delivery properties

A collection of homologous monodisperse facial amphiphiles consisting of an α-, β- or γ-cyclodextrin (α, β or γCD) platform exposing a multivalent display of cationic groups at the primary rim and bearing hexanoyl chains at the secondary hydroxyls have been prepared to assess the influence of the cyclooligosaccharide core size in their ability to complex, compact and protect pDNA and in the efficiency of the resulting nanocondensates (CDplexes) to deliver DNA into cells and promote transfection in the presence of serum. All the polycationic amphiphilic CDs (paCDs) were able to self-assemble in the presence of the plasmid and produce transfectious nanoparticles at nitrogen/phosphorous ratios ≥5. CDplexes obtained from βCD derivatives generally exhibited higher transfection capabilities, which can be ascribed to their ability to form inclusion complexes with cholesterol, thereby enhancing biological membrane permeability. The presence of thiourea moieties as well as increasing the number of primary amino groups then favour cooperative complexation of the polyphosphate chain, enhancing the stability of the complex and improving transfection. In the α and γCD series, however, only the presence of tertiary amino groups in the cationic clusters translates into a significant improvement of the transfection efficiency, probably by activating endosome escape by the proton sponge mechanism. This set of results illustrates the potential of this strategy for the rational design and optimisation of nonviral gene vectors.     

Synthesis and Kerr effect of p-phenylene vinylene oligomers

The molecular dynamics of p-phenylene vinylene (PPV) oligomers, synthesised by a condensation reaction and separated by molecular distillation, have been investigated using the electrooptic Kerr effect. The experimental Kerr constants of these materials change sign from positive to negative in going from n = 1 to n = 2 and are not in good agreement with theoretical results. The discrepancies, which increase in magnitude as n increases, can be attributed to solvent-solute interactions, the nonplanar nature of PPV oligomers, or the nonvalidity of the additivity scheme chosen for calculation of theoretical quantities. © 1996 John Wiley & Sons, Inc.     

Synthesis of chiral macrocyclic sugar-peptide hybrids by ring closing metathesis approach

Furanoside and peptide appended bis-olefins afforded monomeric 12- to 18-membered cyclic olefins fused to furanoside rings via RCM approach using Grubbs’ Catalyst.     

Synthesis of macrocyclic compounds that are condensed with a pyrazole ring

2-Carbethoxy-[11]--cyclothien-1-one, 2-carbethoxycyclopentadecanone, and 2,15-dicarbethoxy-[9,9]--cyclodithiene-1,14-dione were converted to 2-phenyl-1-methyl-[11]--cyclothieno [1,2-d] pyrazol-3-one, 2-phenyl-1-methyl-4,5-tridecamethylenepyrazol-3-one, and 2,16-diphenyl-1, 15-dimethyl- [9,9]-, -cyclodithienobis [(1,2-d, 14,15-d) pyrazole]-3,17-dione, respectively, by condensation with phenylhydrazine and subsequent methylation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 920–923, July, 1980.     

Synthesis and ring‐opening polymerization of macrocyclic (arylene thioether ketone) oligomers

Macrocyclic (arylene thioether ketone) oligomers together with a linear poly(phenylene sulfide ketone) oligomer were synthesized by a one‐step reaction. The macrocycles and linear oligomer were fully characterized by ¹³C‐NMR, H‐NMR, matrix assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS), differential scanning calorimetry (DSC) and FT‐IR. Uncatalyzed, simultaneously ring‐opening polymerization (ROP) of the macrocycles and the mixture of macrocycles and linear oligomer were carried out under dynamic heating conditions. The ROP temperature of the macrocycles decreased upon mixing it with the linear oligomer. The ROP conditions and mechanism were investigated and discussed. The macrocycles and their mixture show potential applications in high temperature adhesives and sealants. Copyright © 2006 John Wiley & Sons, Ltd.     

Tetrahedron report number 230 : Synthesis of macrocyclic compounds by ring enlargement

A summary of important ring expansion strategies, including recent references, is presented in Section 1. Subsequently the synthesis of macrocyclic ketones, lactams and lactones involving the heterolytic cleavage of the bridge bond in bicyclic intermediates is discussed. Typical applications in the field of natural product synthesis are shown. Finally the ring enlargement strategies are compared, pointing out the advantages and drawbacks of each method.     

Two-component fibers/gels and vesicles formed from hetero-double-helices of pseudoenantiomeric ethynylhelicene oligomers with branched side chains

A methodology for the formation of fibers/gels and vesicles by molecular assembly and for controlling their properties is presented. Two-component systems of pentamer (P)-5 and tetramer (M)-4 pseudoenantiomeric ethynylhelicenes with decyloxycarbonyl (D) and 4-methyl-2-(2-methylpropyl)-1-pentyloxycarbonyl (bD) side-chains have been examined. Distinct aggregates were formed by changing the solvent for the three combinations of (P)-bD-5/(M)-bD-4, (P)-D-5/(M)-bD-4, and (P)-D-5/(M)-D-4. In toluene, (P)-bD-5/(M)-bD-4, (P)-D-5/(M)-bD-4, and (P)-D-5/(M)-D-4 all formed gels and fibrous assemblies were observed by AFM. The minimum gel-forming concentration (MGC) decreased in the order (P)-bD-5/(M)-bD-4>(P)-D-5/(M)-bD-4>(P)-D-5/(M)-D-4. In diethyl ether, vesicular formation was observed by dynamic light scattering (DLS), AFM, and TEM, and the size of the vesicles decreased in the order (P)-bD-5/(M)-bD-4>(P)-D-5/(M)-bD-4>(P)-D-5/(M)-D-4. Both fiber/gel and vesicle formation were accompanied by enhanced CDs and redshifted UV/Vis absorption bands with a change in color to deep yellow. These are novel two-component oligomeric systems that form assemblies of fibers/gels or vesicles depending on the solvent, and the structures and properties of the assemblies can be fine-tuned by changing the combination of oligomers. In m-difluorobenzene, a homogeneous solution was obtained with (P)-D-5/(M)-bD-4, which again exhibits enhanced CDs and redshifted UV/Vis absorptions. Vapor pressure osmometry analysis showed the formation of a bimolecular heteroaggregate. The study has indicated that pseudoenantiomeric oligomers form hetero-double-helices that hierarchically assemble to form fibers/gels and vesicles.     

Synthesis and properties of calixarene analogs incorporating a thiophene unit in the macrocyclic ring

Calixarene analogs containing a thiophene unit in the macrocyclic ring were prepared by a stepwise method. The macrocycles adopt a cone‐like form as the preferred conformation in solution. The induced chemical shift change, nOe experiment, and ¹H relaxation time (T₁) measurement supported the fact that the macrocycle forms a complex with the N‐methylpyridinium salt. In contrast, O‐tetramethylated macrocycles and linear phenol‐formaldehyde tetramer, could not efficiently include the N‐methylpyridinium salt.     

Synthesis of well-defined tower-shaped 1,3,5-trisubstituted adamantanes incorporating a macrocyclic trilactam ring system

We describe the synthesis of two novel well-defined tower-shaped 1,3,5-trisubstituted adamantanes 30 and 33 that incorporate a macrocyclic trilactam ring system. Each nanoscale molecule has a broad tripodal base consisting of three identical sulfur-containing termini as the tripod feet, 4-acetylsulfanylmethylphenyl units in the case of 30 and 3,5-bis(acetylsulfanylmethyl)phenyl units in the case of 33. The sulfur atoms are designed to bind the molecules trivalently to the apex of a gold-coated commercial AFM tip through formation of three S-Au bonds. The rigid adamantane-derived head unit with a single hydrogen atom at the apex is designed to scan the sample. Molecules 30 and 33 are synthesized from 1,3,5-triethynyladamantane by a series of Sonogashira coupling reactions involving terminal alkynes and aryl iodides. A macrocyclic trilactam unit is included for added rigidity. We demonstrate that molecule 30 is sufficiently large and rigid to be visualized by a conventional AFM tip. These nanoscale molecules may also find application as chemically well-defined nanoscale objects for calibration of AFM tips.     

Synthesis of macrocyclic compounds

New representatives of macrocyclic ansa-ketolactones that include a thiophene ring, the differences in the yields of which during intramolecular acylation under high-dilution conditions were compared with the peculiarities of their three-dimensional structures, were synthesized. The mass spectra of the ketolactones were studied.See [1] for communication XVII.Translated from Khimiya Geterotsiklicheskikh, Soedinenii, No. 1, pp. 40–44, January, 1975.