Cyclic Bis Research Articles

Dynamic and Reversible Polymorphism of Self-Assembled Lyotropic Liquid Crystalline Systems Derived from Cyclic Bis(ethynylhelicene) Oligomers.

A self-assembled lyotropic liquid crystal (LLC) system exhibiting dynamic and reversible polymorphism was developed using the synthetic cyclic ethynylhelicene oligomers cyclobis[(M)-D-n] (n = 4 and 6), in which two oligomer moieties are connected by two flexible linkers. The cyclic molecular structure was designed to control aggregation properties ranging from the molecular level to the macroscopic level. The cyclic oligomer changed its structure between random coils and an intramolecular homo-double helix induced by temperature and solvents. In the presence of pseudoenantiomeric acyclic oligomers, cyclobis[(M)-D-4] formed trimolecular complexes with a total molecular weight of over 10 000 Da containing two intermolecular hetero-double helices. The trimolecular complex formation predominated over bimolecular complex formation. The trimolecular complex self-assembled at high concentrations and formed LLCs composed of anisotropically aligned fibers. The result is in contrast to acyclic systems, which form gels composed of randomly oriented fibers. The LLCs changed into turbid gels composed of randomly oriented bundles upon cooling, and the LLCs were regenerated by heating. This is a notable example of a self-assembled LLC system exhibiting dynamic and reversible polymorphism between two ordered structures in a closed system consisting of fully synthetic molecules.

Synthesis of New Bis(amidine)–Cobalt Catalysts and Their Application to Styrene Polymerization

Two new bis(amidine) cobalt(II) complexes were rationally designed and efficiently synthesized. The first synthesized cobalt complex was based on a cyclic bis(amidine) ligand with chiral vicinal diphenyl groups. The structure was verified by single-crystal X-ray crystallography. As expected from the ligand structure, the Co–N bonds in this complex were significantly shorter than those found in the corresponding 1,2-diimine cobalt complex. This indicates that the bis(amidine) ligand has better electron-donating capability than the 1,2-diimine ligand. Upon test polymerization of styrene, the complex exhibited a moderate activity of 5.88 × 105 g PS/(mol Co h). On the basis of this encouraging result, a new 1,2-diaminobenzene-derived bis(amidine) ligand was efficiently synthesized and used to make the corresponding cobalt(II) complex. When subjected to styrene polymerization, the resulting complex showed unusually high polymerization activity [164 × 105 g PS/(mol Co h)] and high conversion (>99%). The resulting polymer was identified as atactic polystyrene by 13C NMR spectroscopy analysis. The significantly enhanced styrene polymerization activity of the 1,2-diaminobenzene-originated bis(amidine) cobalt(II) complex is attributed to the improved electron-donating capability of the ligand.

Synthesis of Novel N-Heterocyclic Carbene-Oxazoline Palladium Complexes and Their Applications in Suzuki-Miyaura Cross-Coupling Reaction

A series of novel N-heterocyclic carbene-oxazoline ligands were synthesized in six steps. Palladium complexes were obtained by deprotonation of the benzimidazole salts and subsequent ligation with Pd(OAc)2 in THF. Different types of cyclic bis- and tetrapalladium complexes were achieved by modifying substituent of oxazoline group. The structures of these palladium complexes were characterized by NMR and X-ray diffraction analysis. Catalytic properties of these Pd-complexes were tested by Suzuki–Miyaura cross-coupling reaction.

Molecular conductors with anti-7,7′:8,8′-bis(dithio)bis(7,8-dicarbaundecaborate) anion

Abstract New radical cation salts (BEDT-TTF)2[anti-7,7′:8,8′-bis(dithio)bis(7,8-dicarba-undecaborate)] and (TMTTF)2[anti-7,7′:8,8′-bis(dithio)bis(7,8-dicarbaundecaborate)] were obtained by electrocrystallization from solution of bis(ortho-carboranyl-1,2-dithiolate)cobalt(II) complex (Me4N)2[Co(1,2-S2C2B10H10)2] and BEDT-TTF or TMTTF, respectively, in acetonitrile – 1,1,2-thrichloroethane. The process is accompanied with the complex demetallation, partial deboronation of the carborane cage and oxidation of dithiolate to cyclic bis(disulfide). X-ray crystal structures and electrical conductivities of the compounds synthesized were determined.

Molecular Networks Created by Charge-Assisted Hydrogen Bonding in Carboxylate Salts of a Bis(amidine)

Amidines can be protonated by carboxylic acids to give amidinium carboxylates, and the ions can associate by forming multiple charge-assisted hydrogen bonds according to reliable motifs. Extended hydrogen-bonded networks can be constructed by treating suitable bis(amidines) with acids containing multiple carboxyl groups. To further explore the potential of this strategy, we have determined the structures of salts produced by treating 2,2′-bi-2-imidazoline, a cyclic bis(amidine), with oxalic, fumaric, terephthalic, and trimesic acids. The structures of the salts proved to incorporate features resulting predictably from the geometry of the ions and their ability to engage in charge-assisted hydrogen bonds.

Atropisomerism of diastereomer diribonucleoside phosphotriester

Abstract Linear diribonucleoside phosphotriester is an important intermediate for synthesizing biologically important compounds, such as cyclic bis(3′–5′) diguanylic acid (c-di-GMP) and its analogues. Atropisomerism of diastereomers generated by the chiral center of the P atom, which results in the doubling of signals in 31 P NMR. The data of 31 P NMR at different temperature are presented, and thereafter the reason is discussed.

Hydrolytic reactions of cyclic bis(3′‐5′)diadenylic acid (c‐di‐AMP)

Hydrolytic reactions of cyclic bis(3′‐5′)diadenylic acid (c‐di‐AMP) have been followed by Reversed phase high performance liquid chromatography (RP‐HPLC) over a wide pH range at 90 °C. Under neutral and basic conditions (pH ≥ 7), disappearance of the starting material (first‐order in [OH−]) was accompanied by formation of a mixture of adenosine 2′‐monophosphate and 3′‐monophosphate (2′‐AMP and 3′‐AMP). Under very acidic conditions (from H0 = −0.7 to 0.2), c‐di‐AMP undergoes two parallel reactions (first‐order in [H+]): the starting material is cleaved to 2′‐AMP and 3′‐AMP and depurinated to adenine (i.e., cleavage of the N‐glycosidic bond), the former reaction being slightly faster than the latter one. At pH 1–3, isomerization to cyclic bis(2′‐5′)diadenylic acid competes with the depurination. Copyright © 2012 John Wiley & Sons, Ltd.

Synthesis of 2′-Modified Cyclic Bis(3′–5′)diadenylic Acids (c-di-AMPs) and Their Promotion of Cell Division in a Freshwater Green Alga

Abstract Three 2′-modified cyclic bis(3′–5′)diadenylic acids (c-di-AMPs) were synthesized from commercially available adenosine phosphoramidites and the effects of c-di-AMP derivatives on the cell division of Chlamydomonas reinhardtii, a kind of freshwater green algae, were investigated. This structure–activity relationship study suggests that the di(2′-O-methyl)-c-di-AMP showed the highest activity and that 2′-substituents influenced the cell division of C. reinhardtii.

Cyclic bis(β-diketonate)- and bis(β-ketoesterate)-bridged titanium and zirconium alkoxide derivatives

Reaction of Ti(OiPr)(4) with various bis(β-diketones) and bis(β-ketoesters) (LH(2)) results in the formation of dimeric complexes [Ti(OiPr)(2)L](2), where each metal centre is coordinated by two terminal OiPr ligands and two bridging β-diketonate or β-ketoesterate groups (L). Macrocycles containing two M(OiPr)(2) moieties are thus formed. Reaction of Zr(OiPr)(4) with the same bis(β-diketones) and bis(β-ketoesters) results in different compounds, depending on the organic spacer connecting the two functional groups. With shorter spacers, the compounds [ZrL(OiPr)(2)](2)·2iPrOH are obtained, with the same structures as the corresponding titanium complexes. With longer spacers, however, complexes with a higher degree of substitution are formed, such as (ZrL(2))(2) and Zr(2)L(3)(OiPr)(2)·2iPrOH. The molecular weight and structure of all compounds was elucidated by ESI-MS. MS/MS of the corresponding [M+Na](+) precursor ions confirmed the proposed structures based on structure-specific product ions. Solution NMR experiments and DFT calculations additionally supported the proposed structures.

Direct entry to erythronolides via a cyclic bis[allene

The complexity and low tractability of antibiotic macrolides pose serious challenges to addressing the problem of resistance through semi- or total synthesis. Here we describe a new strategy involving the preparation of a complex yet tractable macrocycle and the transformation of this macrocycle into a range of erythronolide congeners. These compounds represent valuable sectors of erythromycinoid structure space and constitute intermediates with the potential to provide further purchase in this space. The routes are short. The erythronolides were prepared in three or fewer steps from the macrocycle, which was prepared in a longest linear sequence of 11 steps.

Coordinatively Saturated Tris(oxazolinyl)borato Zinc Hydride-Catalyzed Cross Dehydrocoupling of Silanes and Alcohols

The four-coordinate zinc compound ToMZnH (1, ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) catalyzes selective alcoholysis of substituted hydrosilanes. The catalytic reaction of PhMeSiH2 and aliphatic alcohols favors the monodehydrocoupled product PhMeHSi–OR. With the aryl alcohol 3,5-C6H3Me2OH, the selectivity for mono(aryloxy)hydrosilane PhMeHSiOC6H3Me2 and bis(aryloxy)silane PhMeSi(OC6H3Me2)2 is controlled by relative reagent concentrations. Reactions of secondary organosilanes and diols provide cyclic bis(oxo)silacycloalkanes in high yield. The empirical rate law for the ToMZnH-catalyzed reaction of 3,5-dimethylphenol and PhMeSiH2 is −d[PhMeSiH2]/dt = k′obs[ToMZnH]1[3,5-C6H3Me2OH]0[PhMeSiH2]1 (determined at 96 °C) which indicates that Si–O bond formation is turnover-limiting in the presence of excess phenol.

Modeling the Direct Activation of Dihydrogen by a P2C2-Cyclic Biradical: Formation of a Cyclic Bis(P-H λ5-phosphorane)

1-tert-Butyl-3-methyl-2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl reacts with hydride followed by proton quench to give a 2,4-diphospha-1,3-cyclobutadiene with diylidic structure.

Formation of a cyclic bis(iminophosphorane) from a 2,2′‐bis(phosphino)azobenzene via NN bond cleavage

AbstractAn eight‐member cyclic bis(iminophosphorane) was synthesized by treatment of 2,2′‐bis(phosphino)azobenzene with pentachlorophenol via NN bond cleavage of the azobenzene. The crystal structure of the cyclic bis(iminophosphorane) was determined by the X‐ray crystallographic analysis. A study on the reaction mechanism showed that both protonation of the azo moiety and intramolecular nucleophilic attacks of the phosphino groups played a key role in the formation of the bis(iminophosphorane) from the azo compound bearing two phosphino groups. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:301–306, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20680

ChemInform Abstract: Platinum Complex Catalyzed Dehydrogenative Double Silylation of Olefins and Dienes with o-Bis(dimethylsilyl)benzene.

Abstract Olefins underwent dehydrogenative 1,2- and/or 1,1-double silylation with o-bis(dimethylsilyl)benzene (1) in the presence of a catalytic amount of Pt(CH2CH2)PPh3)2 to afford benzo-1,4-disilacyclohexene (3) and/or benzo-1,3-disilacyclopentene (4) derivatives, respectively. In reactions of aliphatic olefins, single hydrosilylation with one of the SiH bonds took place as a side reaction to give HMe2Si(o-C6H4)SiMe2R compounds. Depending on the conditions of the latter reactions, HMeRSi(o-C6H4)SiMe3 compounds arising from 1,4-rearrangement of a methyl group were also formed. The cyclic bis(silyl)platinum complex Me2 Si(o-C 6 H 4 )SiMe 2 P t(PPh3)2 (11) formed upon treatment of 1 with the platinum-ethylene complex readily reacted with olefins in the presence of 1 to afford 3 and/or 4. Compound 4 coming from the catalytic reaction of styrene with o-bis(deuteriodimethylsilyl)benzene did not have the deuterium label incorporated. Based on these results, the dehydrogenative double silylation is proposed to take place via 11 as a key intermediate.

Bis[2-(2,4-dinitrobenzyl)pyridinium] biphenyl-4,4′-disulfonate trihydrate

In the structure of the title salt, 2C12H10N3O4 +·C12H8O6S2 2−·3H2O, determined at 173 K, the biphenyl-4,4′-disulfonate dianions lie across crystallographic inversion centres with the sulfonate groups inter­acting head-to-head through centrosymmetric cyclic bis­(water)-bridged hydrogen-bonding associations [graph set R 4 4(11)], forming chains. The 2-(2,4-dinitro­benz­yl)pyridinium cations are linked to these chains through pyridinium–water N—H⋯O hydrogen bonds and a two-dimensional network is formed through water bridges between sulfonate and 2-nitro O atoms, while the structure also has weak cation–anion π–π aromatic ring inter­actions [minimum ring centroid separation = 3.8441 (13) Å].

Marchantin A, a cyclic bis(bibenzyl ether), isolated from the liverwort Marchantia emarginata subsp. tosana induces apoptosis in human MCF-7 breast cancer cells

Liverwort constituents have been reported to exert a broad spectrum of biological activities. In this study, we used a bioactivity-guided separation of an extract from the liverwort species Marchantia emarginata subsp. tosana to determine its anticancer activity. A high level of the active ingredient was isolated from this liverwort and its chemical structure was identified and characterized by various spectra. It was found to be identical to a well-known compound, marchantin A, a cyclic bisbibenzyl ether. However, no anticancer activities of this compound have previously been reported. We found that marchantin A efficiently induced cell growth inhibition in human MCF-7 breast cancer cells, with an IC 50 of 4.0 μg/mL. Fluorescence microscopy and a Western blot analysis indicated that marchantin A actively induced apoptosis of MCF-7 cells. The levels of cleaved caspase-8, cleaved caspase-3, cleaved caspase-9, and cleaved poly (ADP ribose) polymerase (PARP) increased. However, the level of Bid markedly decreased in a dose- and time-dependent manner. We also evaluated the anticancer activities of marchantin A on the regulation of cell cycle regulators such as p21, p27, cyclin B1, and cyclin D1. The p21 and p27 gene expressions increased markedly while cyclin B1 and D1 gene expression decreased markedly by treatment with marchantin A. Many report demonstrated that liverwort was suggested to possess potent antioxidant activity. Our results indicate that marchantin A possesses free radical-scavenging activity (EC 50 = 20 μg/mL). Taken together, for the first time, the compound marchantin A from liverworts demonstrated to be a potent inducer of apoptosis in MCF-7 cells.

Effect of cyclic bis(3′–5′)diguanylic acid and its analogs on bacterial biofilm formation

Cyclic bis(3′–5′)diguanylic acid (cyclic-di-GMP) functions as a second messenger in diverse species of bacteria to trigger wide-ranging physiological changes. We measured cyclic-di-GMP and its structural analogs such as cyclic bis(3′–5′)guanylic/adenylic acid (cyclic-GpAp), cyclic bis(3′–5′)guanylic/inosinic acid (cyclic-GpIp) and monophosphorothioic acid of cyclic-di-GMP (cyclic-GpGps) for effects on the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. We constructed a knockout mutant of SA0701, which is a GGDEF motif protein relevant to diguanylate cyclase from S. aureus 2507. We confirmed that the biofilm formation of this mutant (MS2507ΔSA0701) was reduced. Cyclic-di-GMP corresponding to physiological intracellular levels given in the culture recovered the biofilm formation of MS2507ΔSA0701, whereas its analogs did not, indicating that unlike a previous suggestion, cyclic-di-GMP was involved in the positive regulation of the biofilm formation of S. aureus and its action was structurally specific. At a high concentration (200 μM), cyclic-di-GMP and its analogs showed suppression effects on the biofilm formation of S. aureus and P. aeruginosa, and according to the quantification study using costat analysis, the suppression potential was in the order of cyclic-di-GMP, cyclic-GpGps, cyclic-GpAp and cyclic-GpIp, suggesting that the suppression effect was not strictly specific and the change of base structure quantitatively affected the suppression activity.

Nonconventional Behavior of NCN-Chelated Organoantimony(III) Sulfide and Isolation of Cyclic Organoantimony(III) Bis(pentasulfide)

Organoantimony(III) sulfide (1) containing the NCN chelating ligand L [L = 2,6-(CH(2)NMe(2))(2)C(6)H(3)] displays unusual dual behavior, being dimeric (LSbS)(2), with the central Sb(2)S(2) core, in the solid state but monomeric in solution. Sulfide 1 reacts with elemental S to give the unprecedented cyclic bis(pentasulfide) LSb(mu-S(5))(2)SbL (2) with the central 12-membered ring Sb(2)S(10).

The cage effect on assembly of cyclic-bis-(zinc porphyrin) with 5,15-dipyridylporphyrin

An inclusion complex of cyclic bis(zinc porphyrin) 1 with 5,15-dipyridylporphyrin derivative 3 has been designed and constructed. The complex formation is induced by Zn-N coordination, and is robust (Kassoc ∼ 106 L/mol) due to the presence of the cage effect of cyclic bis(zinc porphyrin). The cage-like complex as an entity is stable enough, and also convenient to achieve relative movement between the bis(zinc porphyrin) host and the dipyridylporphyrin guest connected by Zn-N coordination. The characteristics of these assemblies have been demonstrated by 1 H NMR, UV-vis, and fluorescence spectra. The results show its potential applications as a molecular gyroscope in molecular machines.

ChemInform Abstract: Synthesis, Chemical Properties and Biological Activities of Cyclic Bis(3′‐5′)diguanylic Acid (c‐Di‐GMP) and Its Analogues

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.