A new approach in exciton‐coupled circular dichroism (ECCD)—insertion of an auxiliary stereogenic center

Person, Richard V.; Monde, Kenji; Humpf, Hans‐Ulrich; Berova, Nina; Nakanishi, Koji

doi:10.1002/chir.530070304

Cited by 65 publications

(51 citation statements)

References 7 publications

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“…215 nm, of a sign predicted by application of the lactam octant rule [30,31], as indicated in Figure 3, and also similar to that seen in the CD spectrum of (R)-(-)-4-hydroxypiperidin-2-one [32]. Although more detailed studies are necessary to fully assign the CE's described to specific electronic transitions or exciton coupling effects [33,34], these observations provide a reference for chiroptical properties in similar systems.…”

Section: Cd-spectroscopymentioning

confidence: 86%

Enantiodivergent Synthesis of (R)- and (S)-Rolipram

et al. 1998

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Both enantiomers of rolipram (1) have been prepared in large quantity from a common intermediate rac-3-(3'-cyclopentyloxy-4'-methoxy)phenyl-4-nitro butyric acid (6), which was resolved by way of the two readily separable diastereoisomeric amides obtained with (S)-(−)-phenylethylamine. Reduction of the nitro group and intramolecular transamidation gave (R)-(−)-1 and (S)-(+)-1, respectively. CD spectra of both enantiomers of rolipram are reported and discussed. Both enantiomers of rolipram presented the same potency of inhibitory activity against recombinant cyclic-AMP-selective phosphodiesterase (PDE4) subtypes.

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Section: Cd-spectroscopymentioning

confidence: 86%

Enantiodivergent Synthesis of (R)- and (S)-Rolipram

et al. 1998

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“…However, the CD spectrum of compound 2 showed an almost opposite Cotton effect to that of compound 1 . The CD spectra of compounds 1 and 2 confirmed that these two compounds were diastereomers [22,23]. …”

Section: Resultsmentioning

confidence: 84%

Four New Antibacterial Xanthones from the Marine-Derived Actinomycetes Streptomyces caelestis

et al. 2012

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Four new polycyclic antibiotics, citreamicin θ A (1), citreamicin θ B (2), citreaglycon A (3), and dehydrocitreaglycon A (4), were isolated from marine-derived Streptomyces caelestis. The structures of these compounds were elucidated by 1D and 2D NMR spectra. All four compounds displayed antibacterial activity against Staphylococcus haemolyticus, Staphylococcus aureus, and Bacillus subtillis. Citreamicin θ A (1), citreamicin θ B (2) and citreaglycon A (3) also exhibited low MIC values of 0.25, 0.25, and 8.0 μg/mL, respectively, against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300.

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“…From these results, the max at 20°C is attributed to the S-chiral (lefthanded) H-aggregates of the hemicyanine moieties, according to the exciton chirality theory. 7 At the same time, these results indicate that the peptide lipid self-assembles at this concentration (0.1 mM); that is, this concentration is above the critical aggregation concentration of the peptide lipid. Conversely, in a good solvent, ethanol, the hemicyanine moieties did not form Haggregates and had a max at 484 nm ( Figure S7a).…”

Section: ¹1mentioning

confidence: 71%

Enhanced Fluorescence of Loosely Packed Dye Aggregates

Ryu

Hachisako

2015

Chemistry Letters

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The fluorescence of a hemicyanine dye was considerably enhanced by the formation of loosely packed aggregates, compared to tightly aggregated and molecularly dispersed hemicyanine dyes. Loose dye aggregates were realized by introducing a self-assembling unit to the dye molecules and by adjusting the mixture of good solvent and nonsolvent for the dye moiety.The aggregation morphology of organic dyes can greatly affect their fluorescence intensity, wavelength, and lifetime. For example, when arranged in a parallel orientation, the so-called H-aggregation generally causes a significant decrease in fluorescence intensity accompanied by a blue shift of the absorption band with respect to the monomer band.1 Conversely, in a slipped arrangement, the so-called J-aggregation exhibits a narrow red-shifted absorption band which often results in enhanced fluorescence with a very small Stokes shift.1 Therefore, how dye molecules are designed and the way in which their aggregation morphology is controlled are very important for applications of fluorogenic materials (for example, sensors, laser sources, sensitizers, and nonlinear optical materials).Fluorescent dyes are very useful materials and are usually used in solution at low concentration so that the dye molecules do not form aggregates and self-quench. In contrast, a number of dyes have recently been developed that exhibit strongly enhanced fluorescence by the formation of rigid aggregates in the solid (nanoparticles and thin films) 1a,2 or gel 3 states, through a process known as aggregation-induced emission (AIE). This finding has expanded the range of fluorogenic dye applications. Their enhanced fluorescence is caused by, for example, conformational planarization, J-aggregate formation, and physical constraint. The formation of tightly packed dye aggregates has been limited to the solid state or at sufficiently high solution concentrations at which gel formation can occur.In this paper, we demonstrate the fluorescence enhancement of a hemicyanine (stilbazolium) dye based on a new concept, that is, the formation of "loosely packed aggregates" in the sol state. In general, it is difficult to form such loose aggregates in the solution state because dyes can be molecularly dispersed in good solvents, whereas tightly packed dye aggregates are formed in poor-or nonsolvents. We have achieved the formation of loose dye aggregates by functionalizing the dye molecule with an

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A new approach in exciton‐coupled circular dichroism (ECCD)—insertion of an auxiliary stereogenic center

Cited by 65 publications

References 7 publications

Enantiodivergent Synthesis of (R)- and (S)-Rolipram

Enantiodivergent Synthesis of (R)- and (S)-Rolipram

Four New Antibacterial Xanthones from the Marine-Derived Actinomycetes Streptomyces caelestis

Enhanced Fluorescence of Loosely Packed Dye Aggregates

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