Takeharu Haino

Fullerenes Enclosed in Bridged Calix[5]arenes

Host systems that bind C70 preferentially to C60 are found in the bridged calix[5]arenes 1 (X= alkyne bridge). The complexation-induced shifts of the bound fullerene guests provide valuable information on the structure and dynamics of the supramolecular complex.

ISOLATION AND STRUCTURE OF PINNATOXIN D, A NEW SHELLFISH POISON FROM THE OKINAWAN BIVALVE PINNA MURICATA

Abstract A new shellfish poison, pinnatoxin D, has been isolated from the Okinawan bivalve Pinna muricata . The planar structure was elucidated by extensive 2D NMR experiments, and the relative stereochemistry was deduced by NOESY data and 3 J HH coupling constants. Pinnatoxin D is a novel amphoteric carbocyclic compound which is composed of a 6,7-spiro ring, a 5,6-bicyclo ring and a 6,5,6-trispiro ketal involving 15 chiral centers.

Pinnatoxins B and C, the most toxic components in the pinnatoxin series from the Okinawan bivalve Pinna muricata

Abstract Pinnatoxins B and C, the most toxic components in the pinnatoxin series, were successfully purified from the Okinawan bivalve Pinna muricata . Their gross structures were determined based on NMR and MS/MS spectral analyses. Their stereostructures were mainly determined by transformation reactions. Pinnatoxins B and C, C-34 epimers of each other, have an amphoteric macrocycle composed of 6,7-spiro, 5,6-bicyclo and 6,5,6-trispiro ketal rings, the same as in pinnatoxins A and D.

White‐Light‐Emitting Edge‐Functionalized Graphene Quantum Dots

Graphene quantum dots (GQDs) have received considerable attention for their potential applications in the development of novel optoelectronic materials. In the generation of optoelectronic devices, the development of GQDs that are regulated in terms of their size and dimensions and are unoxidized at the sp(2) surfaces is desired. GQDs functionalized with bulky Fréchets dendritic wedges at the GQD periphery were synthesized. The single-layered, size-regulated structures of the dendronized GQDs were revealed by atomic force microscopy. The edge-functionalization of the GQDs led to white-light emission, which is an uncommon feature.

Crystalline supramolecular complexes of C60 with calix[5]arenes

The structure of the crystalline supramolecular complexes of calix[5]arenes ( 1 – 3 ) with C 60 is described. The composite ratios of these complexes are 2:1 for 1 and C 60 and 1:1 for 2 and 3 with the guest. Van der Waals attractive interaction between the heavy halogen atoms on the upper rim of the host ( 1 ) is responsible for the formation of the 2:1 complex.

Induced-Fit Molecular Recognition with Water-Soluble Cavitands

Synthesis of novel water-soluble cavitands 1 and 2 and their complexes--the caviplexes--is described. The solubility in water derives from four primary ammonium groups on the lower rim and eight secondary amide groups on the upper rim. Cavitands 1 and 2 exist as D2d velcraplex dimers in aqueous solution but the addition of lipophilic guests 15-24 induces conformational changes to the vase-like structures. The internal cavity dimensions are 8 x 10 A, and the exchange rates of guests in the caviplexes are slow on the NMR time-scale (room temperature and 600 MHz). The direct observation of bound species and the stoichiometry of the complexes is reported. The association constants (Ka) between 0.4 x 10(-1) (-deltaG295= 0.7 kcalmol(-1)) and 1.4 x 10(2)M(-1) (-deltaG295=2.9 kcalmol(-1)) in D2O and 1.4 x 10(1)(-deltaG295= 1.7 kcalmol(-1)) and 2.8 x 10(4)M(-1)(-deltaG295=6.0 kcalmol(-1)) in [D4]methanol for aliphatic guests 16-24 were determined. Guest exchange rates of the new hosts 1 and 2 are considerably slower than rates observed for typical open-ended cavities in aqueous solution.

UV and IR Spectroscopic Studies of Cold Alkali Metal Ion-Crown Ether Complexes in the Gas Phase

We report UV photodissociation (UVPD) and IR-UV double-resonance spectra of dibenzo-18-crown-6 (DB18C6) complexes with alkali metal ions (Li(+), Na(+), K(+), Rb(+), and Cs(+)) in a cold, 22-pole ion trap. All the complexes show a number of vibronically resolved UV bands in the 36,000-38,000 cm(-1) region. The Li(+) and Na(+) complexes each exhibit two stable conformations in the cold ion trap (as verified by IR-UV double resonance), whereas the K(+), Rb(+), and Cs(+) complexes exist in a single conformation. We analyze the structure of the conformers with the aid of density functional theory (DFT) calculations. In the Li(+) and Na(+) complexes, DB18C6 distorts the ether ring to fit the cavity size to the small diameter of Li(+) and Na(+). In the complexes with K(+), Rb(+), and Cs(+), DB18C6 adopts a boat-type (C(2v)) open conformation. The K(+) ion is captured in the cavity of the open conformer thanks to the optimum matching between the cavity size and the ion diameter. The Rb(+) and Cs(+) ions sit on top of the ether ring because they are too large to enter the cavity of the open conformer. According to time-dependent DFT calculations, complexes that are highly distorted to hold metal ions open the ether ring upon S(1)-S(0) excitation, and this is confirmed by extensive low-frequency progressions in the UVPD spectra.

Supramolecular Polymerization Triggered by Molecular Recognition between Bisporphyrin and Trinitrofluorenone

Self-assembled supramolecular polymers consist of molecular components that are held together through noncovalent interactions. The reversible noncovalent interactions can be used to produce healable, stimuli-responsive, and switchable supramolecular polymers. This new class of intelligent polymer materials, with macroscopic properties that might be turned on and off by external stimuli, has helped supramolecular polymer chemistry to gain momentum within the field of polymer science. The design of wellorganized polymer architectures requires the integration of certain supramolecular components that must be capable of creating the strong noncovalent interactions necessary for producing an appreciable degree of polymerization. Multiple hydrogen-bonding, hydrophobic, cation–dipole, CH/p, and aromatic electron donor–acceptor interactions are often employed in the synthesis of functional supramolecular polymers. Supramolecular porphyrin polymers have recently attracted attention because of their creative applications in photoactive devices. Coordination-driven self-assembly is one of the most useful approaches for building large and elaborate porphyrin architectures. However, self-assembly of porphyrins in organic media, driven by weak noncovalent forces, such as van der Waals and CH/p interactions, is very limited, even though the porphyrin moiety possesses a flat and electron-rich surface that creates the possibility of attractive van der Waals, stacking, and charge-transfer interactions. Recently, we have developed a bisporphyrin cleft connected by a pyridine dicarboxamide linker that assembles to form a unique complementary dimer in organic media. The competitive complexation of a flat, electron-deficient aromatic guest into the bisporphyrin cleft leads to a p donor–acceptortype host–guest complex. These supramolecular motifs should be useful for the synthesis of supramolecular porphyrin polymers. To investigate this strategy, a p donor– acceptor-type host–guest motif was incorporated into the heteroditopic monomer 1. The electron-deficient guest moiety, 4,5,7-trinitrofluorenone-2-carboxylate (TNF), can bind within the bisporphyrin cleft through a charge-transfer interaction, and iterative head-to-tail host–guest complexation should produce a new supramolecular polymer (Figure 1). Herein, we report the novel molecular recognition-directed supramolecular polymerization of monomer 1 in solution and solid state.

Supramolecular polymer formed by reversible self-assembly of tetrakisporphyrin

S-shaped tetrakisporphyrin 2 forms supramolecular polymeric assemblies via a complementary affinity of its bisporphyrin units in solution. The self-association constant determined by applying the isodesmic model is >106 L mol−1, which suggests that a sizable polymer forms at millimolar concentrations at room temperature. The electron deficient aromatic guest (TNF) binds within the molecular clefts provided by the bisporphyrin units via a charge-transfer interaction. This guest complexation completely disrupts supramolecular polymeric assembly. The long, fibrous fragments of the polymeric assemblies were characterized by atomic-force microscopy imaging of a film cast on a mica surface. The polymeric assemblies have lengths of >1μm and show a coiled structure with a higher level of organization. The approach discussed in this report concerning the quick preparation of supramolecular polymeric assemblies driven by noncovalent forces sets the stage for the preparation of a previously undescribed class of macromolecular porphyrin architectures.

Novel high-throughput screening system for identifying STAT3-SH2 antagonists.

Constitutive activation of the oncogenic transcription factor STAT3 frequently occurs in various human malignancies. STAT3 activation involves dimerization via intermolecular pTyr-SH2 interaction. Thus, antagonizing this interaction is a feasible approach to inhibit STAT3 activation for cancer therapy. In order to identify selective STAT3 inhibitors, we developed a biochemical HTS system based on AlphaScreen technology, which measures the abilities of test compounds to antagonize pTyr-SH2 interactions. We screened our chemical libraries using this system and identified 5,15-diphenylporphyrin (5,15-DPP) as a selective STAT3-SH2 antagonist. Selective inhibition of STAT3 nuclear translocation and DNA biding activity was observed in cells treated with 5,15-DPP. IL-6-dependent dimerization of STAT3, c-myc promoter binding and c-myc protein expression were all suppressed by 5,15-DPP, whereas no decrement in either expression or phosphorylation level of STAT3 was observed. Thus, the HTS assay system represented herein may be useful for identifying novel STAT3-SH2 antagonists.