Showing papers by "Yoshihisa Inoue published in 2003"

Supramolecular catalysis of the enantiodifferentiating [4 + 4] photocyclodimerization of 2-anthracenecarboxylate by γ-cyclodextrin

Abstract: 2-Anthracenecarboxylic acid (AC) makes a very stable 1:2 inclusion complex with γ-cyclodextrin (γ-CDx) (K1 = 161 ± 25 M-1, K2 = 38 500 ± 3300 M-1 at 25 °C). The formation of the 1:2 inclusion complex accelerated the photocyclodimerization of AC. The 1:2 inclusion could be clearly verified by UV−vis, CD, and 1H NMR spectroscopies. Although these spectroscopies provide little information about the structural isomers of the inclusion complex, there should be several structural isomers of the 1:2 inclusion complex which have a different longitudinal orientation of the guest molecules in the cavity. The isomer distribution of the photodimerization product primarily depends on the population of these orientational isomers of the 1:2 inclusion complex in the ground state before photoreaction, because, in the lifetime of the excited singlet state, exchanging the orientation is impossible. The enantioselectivity of the photodimerization originates from the difference in the stability of the diastereomeric pair of ...

Bovine serum albumin-mediated enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate.

Abstract: Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxyalate (AC) was performed at 25 °C in aqueous buffer solution (pH 7) in the presence of bovine-serum albumin (BSA) to afford four [4 + 4] cyclodimers, i.e., anti- and syn-head-to-tail (HT) (1 and 2) and anti- and syn-head-to-head (HH) dimers (3 and 4), of which only 2 and 3 are chiral. We found that (1) BSA possesses four sets of binding sites for AC of different affinities, stoichiometries, and chiral environment for photoreaction, which bind 1, 3, 2, and 3 AC molecules with binding constants of 5.3 × 107, 1.3 × 105, 1.4 × 104, and 3.0 × 103 M-1, respectively, (2) the regioselectivity of photodimerization is switched from HT to HH by adding BSA (the HH/HT ratio varies from 0.28 to 4.3), (3) BSA-mediated photodimerization of AC affords optically active products 2 and 3 of up to 29% and 41% ee, respectively. It is emphasized that the selective excitation of bound substrate, utilizing the spectral shift upon complexation with BSA, is not a p...

Solid-state supramolecular chirogenesis: high optical activity and gradual development of zinc octaethylporphyrin aggregates.

Abstract: Aggregationprocessesleadingtochiralitytransferorinduc-tionoramplificationphenomenaarecurrentlyoneofthe“hottopics”ofmodernchemicalscience.Theinvestigationofsuchprocesses has influenced research in many areas includingstudies on the origin of the homochirality of life, variousbiomimeticsystems,materialsandpolymerscience,nonlinearoptics, molecular devices, molecular recognition, and thedetermination of absolute configuration.

Microenvironmental polarity control of electron-transfer photochirogenesis. Enantiodifferentiating polar addition of 1,1-diphenyl-1-alkenes photosensitized by saccharide naphthalenecarboxylates.

Abstract: Enantiodifferentiating polar photoaddition of alcohol to 1,1-diphenylpropene and 1,1-diphenyl-1-butene sensitized by saccharide naphthalene(di)carboxylates was performed in nonpolar to polar solven...

Supramolecular Self-Assemblies of β-Cyclodextrins with Aromatic Tethers: Factors Governing the Helical Columnar versus Linear Channel Superstructures

Abstract: A series of 6-O-(p-substituted phenyl)-modified β-cyclodextrin derivatives, i.e., 6-O-(4-bromophenyl)-β-CD (1), 6-O-(4-nitrophenyl)-β-CD (2), 6-O-(4-formylphenyl)-β-CD (3), 6-phenylselenyl-6-deoxy-β-CD (4), and 6-O-(4-hydroxybenzoyl)-β-CD (5), were synthesized, and their inclusion complexation behavior in aqueous solution and self-assembling behavior in the solid state were comparatively studied by NMR spectroscopy, microcalorimetry, crystallography, and scanning tunneling microscopy. Interestingly, (seleno)ethers 1−4 and ester 5 displayed distinctly different self-assembling behavior in the solid state, affording a successively threading head-to-tail polymeric helical structure for the (seleno)ethers or a mutually penetrating tail-to-tail dimeric columnar channel structure for the ester. Combining the present and previous structures reported for the relevant β-CD derivatives, we further deduce that the pivot heteroatom, through which the aromatic substituent is tethered to β-CD, plays a critical role in ...

Use of an Immobilized/Soluble Hybrid ATRP Catalyst System for the Preparation of Block Copolymers, Random Copolymers, and Polymers with High Degree of Chain End Functionality

Abstract: An immobilized/soluble hybrid catalyst system (CuBr/PS8-dMbpy)/(CuBr2/Me6TREN) for atom transfer radical polymerization (ATRP) was applied to the preparation of polymers exhibiting various architectures. Polymers with high degree of halogen chain end functionality (∼85%) were obtained using the hybrid catalyst system ensuring high efficiency of chain extension reactions through successive monomer addition, affording block (tapered) copolymers. Use of the immobilized catalyst also allowed the synthesis of block copolymers using macroinitiators synthesized by other mechanisms, such as poly(dimethylsiloxane). In the copolymerization of MMA and n-butyl acrylate, the molecular weight, molecular weight distribution, kinetics, and reactivity ratios were similar to those in a conventional homogeneous ATRP, indicating the chemical nature of the polymerization intermediates are similar for both systems. These examples demonstrate the broad applicability of the hybrid catalyst system to various ATRP processes.

Structural and photophysical characterisation of coordination and optical isomers of mononuclear ruthenium(II) polypyridyl 1,2,4-triazole complexes

Abstract: The X-ray crystal structure of the N2 isomers of the Ru(bipy)2 complexes of Hphpztr (1) and Hpztr (2), (bipy = 2,2′-bipyridine, Hphpztr = 2-(5′-phenyl-4′H-[1,2,4]triazol-3′-yl)pyrazine and Hpztr = 2-(4′H-[1,2,4]triazol-3′-yl)pyrazine) are reported. The molecular structure obtained for 2 demonstrates an interesting structural aspect in the sharing of a single proton between two molecular units. The isolation of the Δ and Λ stereoisomers of 1 and [Ru(phen)2(pztr)]+ (phen = 1,10-phenanthroline) (3) by semipreparative HPLC is also reported. The compounds obtained are characterised by electronic spectroscopy and particular attention is paid to the photophysical properties of Δ and Λ isomers of 1 and 3, in chiral enantiopure and racemic solvents.

Selective binding of steroids by 2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(beta-cyclodextrin): fluorescence enhancement by guest inclusion.

Abstract: A novel bis(β-cyclodextrin) was synthesized, and its binding behavior with steroids was investigated to demonstrate that the cooperative co-inclusion of guest and tether by two cyclodextrin moieties is operative to afford the highest molecular selectivity of up to 3.6 for deoxycholate over taurocholate.

Pressure control of enantiodifferentiating photoisomerization of cyclooctenes sensitized by chiral benzenepolycarboxylates. The origin of discontinuous pressure dependence of the optical yield.

Abstract: Pressure effects on enantiodifferentiating geometrical photoisomerizations of (Z)-cyclooctene and (Z,Z)-cycloocta-1,5-diene sensitized by chiral benzene-1,2,4,5-tetracarboxylate were investigated over a pressure range of 0.1–750 MPa. Enantiomeric excesses (ee's) of the (E)- and (E,Z)-isomers obtained displayed discontinuous pressure dependencies, affording distinctly different differential activation volumes (ΔΔV‡) for each range, indicating alteration of the enantiodifferentiation mechanism. The switching of ΔΔV‡ occurred at essentially the same pressures of 200 and 400 MPa, which are shared by all the chiral sensitizers, irrespective of the chiral auxiliary employed. Circular dichroism spectral examinations at pressures of up to 400 MPa also revealed that the chiral sensitizers undergo discontinuous conformational changes at 200 MPa, which most likely lead to switching of the enantiodifferentiating sensitization mechanism in the exciplex intermediate.

Synthesis of Phosphoryl-Tethered β-Cyclodextrins and Their Molecular and Chiral Recognition Thermodynamics

Abstract: Two novel phosphoryl-bridged bis- and tris(β-cyclodextrin)s of different tether lengths, i.e., bis[m-(N-(6-cyclodextryl)-2-aminoethylaminosulfonyl)phenyl]-m-(chlorosulfonyl)phenylphosphine oxide (5...

An Acid–Base Controlled Molecular Switch. syn–anti Conformational Switching in a μ-oxo Bis(Iron Porphyrin)

Abstract: It was found that FeD adopted a stable syn conformation as a result of the inclusion of atomic oxygen in a μ-oxo fashion, but on exposure to acidic conditions converted into the extended anti form. When this was subsequently made basic the syn conformation was re-adopted, simply due to re-inclusion of atomic oxygen forming the μ-oxo species. It was found that the combination of these affects allowed FeD to undergo repeated conformational switching cycles that were reproducible and robust.

Acid-controlled photoreactions of aryl alkanoates: competition of transesterification, decarboxylation, Fries-rearrangement and/or transposition

Abstract: 2,4,6-Trimethylphenyl (mesityl) cyclohexanecarboxylate 1c and related mesityl esters 1a,b and d–f were photodecarboxylated upon irradiation at 254 nm in neutral solvents to give alkylmesitylenes 15 in good yields. In contrast, in the presence of a catalytic amount of acid and a sufficient amount of alcohol, the same compounds underwent facile phototransesterification to afford the corresponding ester 9 and phenol 10 in almost quantitative yields. Photolyses of less-substituted aryl alkanoates such as 2,6-dimethylphenyl (xylenyl), phenyl, 4-methoxyphenyl (4-anisyl) and 4-methoxynaphthyl alkanoates 2–4 and 8 were also investigated to elucidate the reaction mechanism of acid-catalyzed phototransesterification. Irradiation of these esters afforded the corresponding photo-Fries rearrangement products 20–23 both in neutral and acidic acetonitrile with significant acceleration of the processes in the presence of acid. It was elucidated that the photolysis of the esters affords the geminate radical pair 28, which in turn recombines to cyclohexadienone intermediates 29 and 30. Added acid accelerates not only the nucleophilic attack of alcohol to 29 and 30 but also other processes. Prolonged irradiation of the esters in neutral solution led to skeletal rearrangements of the initial product, affording isomeric alkylbenzenes. The phototransposition of cyclohexylmesitylene 15cvia benzvalene intermediates was, on the contrary, retarded under acidic conditions. These acid-controlled competitive photoreactions are representative examples, in which a catalytic amount of acid can alter the fate of reactive intermediates on both ground-state and excited-state surfaces.

Selective Binding of Steroids by 2,2′‐Biquinoline‐4,4′‐dicarboxamide‐Bridged Bis(β‐cyclodextrin): Fluorescence Enhancement by Guest Inclusion.

Abstract: A novel bis(â-cyclodextrin) was synthesized, and its binding behavior with steroids was investigated to demonstrate that the cooperative co-inclusion of guest and tether by two cyclodextrin moieties is operative to afford the highest molecular selectivity of up to 3.6 for deoxycholate over taurocholate. Introduction of a chromogenic group to a cyclodextrin (CD) host not only alters the original binding ability and selectivity but also provides us with a spectral probe for investigating the inclusion complexation behavior with optically silent guest molecules, as the chromogenic aromatic group originally accommodated in the CD cavity suffers substantial conformational changes upon guest inclusion, accompanying appreciable spectral changes. Hence, the binding ability of modified CDs can be quantitatively assessed by analyzing the spectral changes induced by guest inclusion. Indeed, a variety of modified CDs with fluorescent aromatic groups have been synthesized, and their inclusion complexation behavior has been investigated with chiral steroids and alcohols by fluorometric titration to give relatively good molecular selectivities.1-6 Furthermore, bis-CDs tethered by a simple spacer are known to exhibit greatly enhanced binding abilities, compared to those shown by native and modified mono-CDs, through the cooperative binding of one guest molecule with two hydrophobic CD cavities located in a close vicinity.7-14 Nevertheless, dimeric CDs linked by a chromogenic bridge have rarely been reported so far.15 In this work, we report the synthesis of bis-â-CD with a fluorescent 2,2′-biquinoline-4,4′-dicarboxamide tether (1) and its inclusion complexation behavior with chiral steroids. The binding constants (KS) obtained for a series of structurally related steroids (Chart 1) are discussed in terms of the cooperative binding and induced-fit interactions between the steroid guests and dimeric host 1. It is also of our particular interest to examine the role of originally self-included tether group of 1 upon complexation with the steroid guests. N,N′-Bis(2-aminoethyl)-2,2′-biquinoline-4,4′-dicarboxamide-bridged bis-â-CD 1 was synthesized as follows. 2,2′biquinoline-4,4′-dicarboxylic dichloride16,17 (0.30 g, 0.8 mmol) was dissolved in dry DMF (30 mL) containing dicyclohexylcarbodiimide (0.7 g, 34 mmol), to which were added dry 6-(2-aminoethylamino)-6-deoxy-â-CD18 (3.0 g, 2.55 mmol) and dry pyridine (25 mL). The resultant mixture was stirred for 20 h in an ice bath and for an additional 2 days at room temperature, and then the precipitate formed was removed by filtration and the * To whom correspondence should be addressed. Tel: +86-2223503625. Fax: +86-22-3625 or 4853. † Nankai University. ‡ Osaka University. (1) Wallimann, P.; Marti, T.; Fürer, A.; Diederich, F. Chem. Rev. 1997, 97, 1567. (2) Nakamura, M.; Ikeda, A.; Ise, N.; Ikeda, H.; Toda, F.; Ueno, A. J. Chem. Soc., Chem. Commun. 1995, 721. (3) Ikeda, H.; Nakamura, M.; Ise, N.; toda, F.; Ueno, A. J. Org. Chem. 1997, 62, 1411. (4) Ikeda, H.; Nakamura, M.; Ise, N.; Oguma, N.; Nakamura, A.; Ikeda, T.; Toda, F.; Ueno, A. J. Am. Chem. Soc. 1996, 118, 10980. (5) Aoyagi, T.; Nakamura, A.; Ikeda, H.; Ikeda, T.; Mihara, H.; Ueno, A. Anal. Chem. 1997, 69, 659. (6) Kuwabara, T.; Nakajima, H.; Nanasawa, M.; Ueno, A. Anal. Chem. 1999, 71, 2844. (7) De Jong, M. R.; Engbersen, J. F. J.; Huskens, J.; Reinhoudt, D. N. Chem. Eur. J. 2000, 6, 4034. (8) Liu, Y.; Chen, Y.; Li, L.; Zhang, H.-Y.; Liu, S.-X.; Guan, X.-D J. Org. Chem. 2001, 66, 8518. (9) (a) Liu, Y.; Chen, Y.; Li, B.; Wada, T.; Inoue, Y.Chem. Eur. J. 2001, 7, 2528. (b) Liu, Y.; Chen, Y.; Liu, S.-X.; Guan, X.-D.; Wada, T.; Inoue, Y. Org. Lett. 2001, 3, 1657. (10) Baugh, S. D. P.; Yang, Z. W.; Leung, D. K.; Wilson, D. M.; Breslow, R. J. Am. Chem. Soc. 2001, 123, 12488. (b) Nelissen, H. F. M.; Schut, A. F. J.; Venema, F.; Feiters, M. C.; Nolte, R. J. M. Chem. Commun. 2000, 577. (11) Leung, D. K.; Yang, Z. W.; Breslow, R. Proc. Nat. Acd. Sci. U.S.A. 2000, 97, 5050. (12) Michels, J. J.; Huskens, J.; Reinhoudt, D. N. J. Am. Chem. Soc. 2002, 124, 2056. (13) Venema, K.; Rowan, A. E.; Nolte, R. J. M. J. Am. Chem. Soc. 1996, 118, 257. (14) Hishiya, T.; Asanuma, H.; Komiyama, M. J. Am. Chem. Soc. 2002, 124, 570. (15) Breslow, R.; Halfon, S.; Zhang, B. Tetrahedron 1995, 51, 377. (16) Lesesne, S. D.; Henze, H. R. J. Am. Chem. Soc. 1942, 8, 1897. (17) Gershuns, A. L.; Pavlyuk, A. A. Ukr. Khim. Zh. 1964, 30, 955. (18) Matsui, Y.; Tanemura, E.; Nonomura, T. Bull. Chem. Soc. Jpn. 1993, 66, 2847. 10.1021/jo026908k CCC: $25.00 © 2003 American Chemical Society J. Org. Chem. 2003, 68, 3687-3690 3687 Published on Web 04/05/2003 filtrate was evaporated under a reduced pressure to dryness. The residue was dissolved in water, and the aqueous solution was poured into acetone (200 mL) to give a red precipitate. The crude product obtained was dried and purified by column chromatography over Sephadex G-25 with distilled deionized water as an eluent to give pure bis-â-CD 1 in 35% yield as a red solid. 1H NMR (300 MHz, DMSO-d6, TMS): δ 1.0-2.0 (m 8H), 4.4-4.7 (m 12H), 4.8-5.2 (m 14H), 5.4-6.2 (m 28H), 7.69.4 (m Ar 10H). IR (KBr): ν/cm-1 3343, 2929, 2056, 1708, 1661, 1642, 1592, 1549, 1427, 1331, 1238, 1202, 1153, 1078, 1031, 944, 850, 757, 706, 577. UV-vis (water): λmax/ nm ( /M-1 cm-1) 264.6 (37280), 339.0 (15480). Anal. Calcd for C108H164O72N6‚8H2O: C, 46.22; H, 6.32; N, 2.99. Found: C, 46.35; H, 6.31; N, 3.10. To elucidate the conformation of 1, circular dichroism and 1H NMR spectral studies were performed by using a JASCO-750S and a Varian Mercury VX300 spectrometer, respectively. It is well-known that there is a balance between inclusion and dissociation of modified cyclodextrins in solution, so the cross-peaks arising from space correlations between host and guest present both inside protons (H-3/H-5)and outside protons (H-2/H-4) of the CD in the NOESY spectra. In the present observation, we mainly deduce selfand co-inclusion modes with guests from 2D NMR spectra. As shown in Figure 1, the 2D NOESY spectrum of 1 in D2O shows six cross-peaks between the spacer’s aromatic protons and the CD’s interior protons. The cross-peaks A, B, and C, which are assigned to the NOE with the CD’s H-5 protons, unambiguously indicate inclusion of the spacer moiety into the CD cavity. Since the H-5 protons are located at the primary side of the cavity, we may conclude that the biquinoline spacer penetrates into the CD cavity from the narrower opening. However, no cross-peaks are found between the biquinoline’s 3,3′or 5,5′-protons and the CD protons. Hence, it is likely that the unsubstituted rings of biquinoline penetrate into the CD cavities only shallowly from the primary side. The self-inclusion behavior of spacer group in 1 can also be verified by the circular dichroism spectral studies, as the inclusion of achiral chromophoric guest/moiety leads to the induced circular dichroism.19 The circular dichroism spectrum of 1 exhibited two negative Cotton effect peaks of moderate intensities at 225 nm (∆ -3.83 M-1cm-1) and 283 nm (∆ -2.22 M-1cm-1), which may be assigned to the La and Lb bands, respectively. The sign of induced Cotton effect enables us to elucidate the conformation of biquinoline unit in 1. The negative Cotton effects observed for the La and Lb bands indicate that the biquinoline unit is shallowly included into the two CD cavities of 1 in the longitudinal direction,20-22 which is in good agreement with the 2D NMR spectral study. Fluorescence spectral study provides further supports for this complex mode. Dipotassium 2,2′-biquinoline-4,4′dicarboxylate (2), as a reference fluorophore, gave only weak emission as shown in Figure 2 (trace a), but the fluorescence intensity of 2 was significantly enhanced upon addition of mono[6-(2-aminoethylamino)-6-deoxy]â-CD (trace b in Figure 2), most probably through the inclusion of biquinolinedicarboxylate 2 in the CD cavity. Notably, much stronger fluorescence was observed for free 1 under the identical conditions (trace c in Figure 2), which is ascribed to the cooperative binding of the biquinoline spacer by the dual hydrophobic cavities, leading to more effective shielding of the fluorophore from the deactivating water attack. Unexpectedly, the fluorescence intensity was not reduced but significantly enhanced upon addition of steroid guest (trace d in Figure 2). It is well documented that the emission of fluorophoreappended mono-CDs is quenched upon guest inclusion (including steroids),1-6 as a consequence of decomplexation of the initially self-included fluorophore moiety. (19) Harata, K.; Uedaira, H. Bull. Chem. Soc. Jpn. 1975, 48, 375. (20) Kajtar, M.; Horvath, T. C.; Kuthi, E.; Szejtli, J. Acta Chim. Acad. Sci. Hung. 1982, 110, 327. (21) Kodaka, M. J. Am. Chem. Soc. 1993, 115, 3072. (22) Bright, F. V.; Catena, G. C. Anal. Chem. 1989, 61, 905. CHART 1. Molecular Structures of Guests FIGURE 1. 1H NOESY spectrum (300 MHz) of dimer 1 (1.0 × 10-3 M) in D2O at 298 K with a mixing time of 800 ms. 3688 J. Org. Chem., Vol. 68, No. 9, 2003 Hence, we need another mechanism to explain the enhanced fluorescence intensity upon addition of steroid guests observed specifically with dimeric host 1. The increased fluorescence intensity can be rationalized by the increased microenvironmental hydrophobicity and/ or steric shielding around the fluorophore arising from the cooperative guest-tether-host interactions. A 2D NMR study is expected to reveal the cooperative binding behavior in more detail. As illustrated in Figure 3, the NOESY spectrum of an equimolar mixture of dimer 1 with deoxycholate (0.5 mM each) displayed clear NOE cross-peaks between CD’s H-5 and biquinoline’s aromatic protons (peak A), indicating that the biquinoline moiety is not driven out of the CD cavity even after the guest inclusion. Furthermore, the protons of deoxycholate gave not only the cross-peak B with biquinoline’s protons but also the cross-peak C with

Enthalpy-entropy compensation upon syn-anti conformational switching of bis-porphyrins by amines and alcohols

Abstract: Upon interaction with amine and alcohol guests, Zn-Zn and Zn-2H ethane-bridged bis-porphyrin hosts undergo dramatic conformational switching from a syn to an anti form. The thermodynamic parameters obtained exhibit excellent linear enthalpy-entropy correlations, which are distinctly different for amines and alcohols but essentially independent of the host structure. Analyses of the compensation plots reveal a more rigid complex structure and more extensive desolvation upon complexation with amines than for alcohols, which may be ascribed to the different nucleophilicity, binding strength, solvation and geometry.

Spectroelectrochemistry of porphyrin containing mono- and hetero-bimetallic systems: Porphyrin-Ru(bpy)3 conjugates

Abstract: The redox behavior of porphyrin-Ru(bpy)3 conjugates is studied by means of spectroelectrochemistry. The redox potentials for the porphyrin freebase, zinc and manganese derivatives are measured and compared to the corresponding monomeric reference porphyrins. Among the porphyrin-Ru(bpy)3 conjugates, the manganese derivative behaved like its monomeric reference compound, the zinc derivative showed moderate differences, and the freebase derivative exhibited the largest differences. These results are understood to originate from the extended orbital overlap of the redox reaction centers. In the case of the freebase derivative, the bpy ligand of the Ru(bpy)3 moiety is spacially very close to one of the porphyrin moiety’s π-system pyrroles, which is acting as a redox reaction center. For the zinc derivative this effect is more moderate; and because the redox reactions in the manganese derivative occur at the manganese central metal, which is too far from the bpy group, the effect is minimal. From the viewpoint ...

Synthesis of Phosphoryl‐Tethered β‐Cyclodextrins and Their Molecular and Chiral Recognition Thermodynamics.

Abstract: Two novel phosphoryl-bridged bis- and tris(β-cyclodextrin)s of different tether lengths, i.e., bis[m-(N-(6-cyclodextryl)-2-aminoethylaminosulfonyl)phenyl]-m-(chlorosulfonyl)phenylphosphine oxide (5...