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A chiral template was constructed from 7-ethynyl-1,5,7-trimethyl-3-azabicyclo[3.3.1]nonan-2-one by Sonogashira cross-coupling with 4,4′′-diiodoterphenyl and was shown to bind the title compound strongly by hydrogen bonding resulting in enantioselectivities of up to 55% enantiomeric excess (ee) in the [4+4] anthracene photodimerization. [ABSTRACT FROM AUTHOR]

Reports have suggested that polar porphyrins such as tetraphenylporphine tetrasulfonate (TPPS) can serve as carbohydrate receptors in water. Here we find that TPPS shows changes in UV-visible absorption when treated with glucose, but that these are best explained by altered aggregation states and not by formation of a closely-bound complex. [ABSTRACT FROM AUTHOR]

In chiral donor–acceptor (D–A) systems, irradiation wavelength plays vital roles in determining the photochemical consequences. Selective excitation of a D–A complex at the charge-transfer (C-T) band affords an excited C-T complex (ECT), while the local-band excitation of D or A may lead to the formation of a conventional exciplex (EX) upon subsequent interaction with the D–A partner. These two excited species, generated from the same D–A pair, may be categorized formally as excited complexes or exciplexes, but should be distinguished, provided that they significantly differ in structure and reactivity. Indeed, ECT and EX exhibit distinctly different temperature-dependent photophysical and photochemical behaviours, which are assignable to the differences in relative stability, conformational flexibility and/or solvation properties. Fine-tuning excitation wavelength further enabled us to discriminate stereoisomeric intramolecular C-T complexes through preferential excitation, as C-T complexes are generally composed of an ensemble of various geometries. Besides temperature and solvent polarity, the excitation wavelength was shown to be employed as an unconventional yet practical tool for critically controlling the chemo-, regio- and stereoselectivities in molecular and supramolecular photochemistry. [ABSTRACT FROM AUTHOR]

A series of 6-(ω-aminoalkylamino)-6-deoxy-γ-cyclodextrins (CDs) 5–8with varying inter-amino distances were synthesized to control the stereoselectivity of [4] photocyclodimerization of 2-anthracenecarboxylate (AC). Complexation behavior of these CD hosts with AC was studied in aqueous solutions by UV-vis and circular dichroism spectral titration. Supramolecular photocyclodimerization of AC mediated by the CDs was performed in water as well as in water–methanol mixture to reveal that aminopropylamino-CD 6leads to the formation of head-to-headphotodimers 3and 4in highest yields, while aminobutylamino-CD 7affords chiral syn-head-to-tailand anti-head-to-headphotodimers 2and 3in highest enantioselectivities. These results indicate that the inter-amino distance critically control the product's stereo- and enantioselectivities through the electrostatic interactions of two anionic AC guests with the dicationic sidechain attached to the γ-CD rim and can be used as a convenient, yet effective, tool for manipulating the stereochemical outcomes of supramolecular photochirogenesis. [ABSTRACT FROM AUTHOR]

Chiral variants of amyloid fibrils prepared by agitating acidified solutions of bovine insulin at 45 °C not only induced quasi-mirror-imaged circular dichroism spectra upon complexation with 2-anthracenecarboxylate but also gave anti-head-to-head-cyclodimers of the opposite absolute configurations upon photoirradiation. [ABSTRACT FROM AUTHOR]

Mutant human serum albumins accelerated the photocyclodimerization of 2-anthracenecarboxylate to afford chiral cyclodimers in 75–85% enantiomeric excesses, revealing that the mutations to impair non-productive sites 1 and/or 2 enhanced the substrate binding to site 3 without seriously damaging its inherently high photochirogenic ability. [ABSTRACT FROM AUTHOR]

Pyromellitate-bridged cyclodextrin nanosponges (CDNSs) evolved from sol into gel state upon gradual increase of the concentration from 0.2 to 2000 mg mL−1 in water. The enantiodifferentiating geometrical photoisomerizations of (Z)-cyclooctene and (Z,Z)-1,3-cyclooctadiene sensitized by CDNS at various concentrations were critically affected by the phase transition of CDNS to afford the corresponding (E)- and (E,Z)-isomers in the highest enantiomeric excesses in the gel state. [ABSTRACT FROM AUTHOR]

Stereochemical outcomes were critically tuned by excitation wavelength in the supramolecular photocyclodimerization of 2-anthracenecarboxylic acid mediated by native and diamino-modified γ-cyclodextrins. [ABSTRACT FROM AUTHOR]

A newly synthesized chromophore-modified curdlan functions as a saccharide chemosensor in aqueous solution, enabling us to discriminate tetrasaccharide acarbose from 24 mono-, di-, tri-, and tetrasaccharides. [ABSTRACT FROM AUTHOR]

Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid and its alkali metal salts performed in a chiral ionic liquid gave chiral cyclodimers in good enantiomeric excesses of up to 41%, which is the highest ever reported for a photochirogenic reaction in chiral media. [ABSTRACT FROM AUTHOR]

Density functional theory calculations demonstrate that Al(III)-catalyzed conversion of glyoxal to glycolic acid proceeds via a 7-membered dual Lewis acid-hydrogen bonding activation transition state of the 1,2-hydride shift, rather than the previously proposed 5-membered metal-alkoxide chelate activation transition state. [ABSTRACT FROM AUTHOR]

Density functional theory calculations demonstrate that Al(iii)-catalyzed conversion of glyoxal to glycolic acid proceeds viaa 7-membered dual Lewis acid-hydrogen bonding activation transition state of the 1,2-hydride shift, rather than the previously proposed 5-membered metal-alkoxide chelate activation transition state. [ABSTRACT FROM AUTHOR]