Amino acid recognition by fine tuning the association constants: Tailored naphthalimides in pillar[5]arene-based indicator displacement assays

Three aminonaphthalimide derivatives were synthesized bearing different anchoring groups in their 4-position in order to adjust the supramolecular interactions with carboxylato-pillar[5]arene (WP5), an anionic, water-soluble host. The modification of the anchor groups resulted in varying association constants embracing three orders of magnitude (Ka from ∼103 to ∼106) in buffered water. Since the fluorophore responded significantly to the electronic environment, large fluorescence quenching was observed with the anionic WP5 host. The naphthalimide indicator-WP5 supramolecular assemblies were used to detect arginine and lysine with complete selectivity over other non-basic α-amino acids by turn-on fluorescence. The same assemblies proved to be highly sensitive fluorescence displacement assays for the detection of cadaverin

Pillararene-based fluorescent indicator displacement assay for the selective recognition of ATP

The complexation of the cationic, water soluble ammonium pillar6arene was investigated with Dapoxyl sodium sulfonate. Large fluorescence enhancement was observed upon partial inclusion and the resulting complex was used as the first pillararene-based indicator displacement system for the selective recognition of adenosine-5'-triphosphate

Optical spectroscopic studies on the complexation of stilbazolium dyes with a water soluble pillar[5]arene

The host-guest interactions of a water soluble carboxylato-pillar[5]arene (WPA5) and three stilbazolium dyes (containing 9-anthryl, 1-pyrenyl and 4-dimethylaminophenyl groups) were studied by UV-Vis and fluorescence spectroscopy giving a detailed description of the spectral changes. A different spectroscopic response was observed in each case, with the most significant result of 28-fold fluorescence enhancement and intense color change in the case of 4-dimethylaminostyryl-N-methylpyridinium iodide (DAST, G3). In addition, a FID (fluorescence indicator displacement) system comprised of WPA5 and G3 was shown to detect paraquat by turn-off fluorescence in aqueous solution

Resolution of 1-n-propoxy-3-methyl-3-phospholene 1-oxide by diastereomeric complex formation using TADDOL derivatives and calcium salts of O,O '-dibenzoyl-(2R,3R)- or O,O '-di-p-toluoyl-(2R,3R)-tartaric acid

The 1-n-propoxy-3-methyl-3-phospholene 1-oxide was prepared in optically active form by extending our resolution methods applying (−)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane (“TADDOL”), (−)-(2R,3R)-α,α,α',α'-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol (“spiro-TADDOL”), as well as the acidic and neutral Ca2+ salts of (−)-O,O’-dibenzoyl- and (−)-O,O’-di-p-toluoyl-(2R,3R)-tartaric acid. In one case, the diastereomeric complex could be identified by single crystal X-ray analysis. The absolute P-configuration of the enantiomers of the phospholene oxide was also determined by CD spectoroscopy. Keywords: Alkoxy-3-phospholene 1-oxide; P-chirality; Resolution methods; Optical isomers; X-ray crystallography; CD-spectroscopy; Absolute P-configuration

An uracil-linked hydroxyflavone probe for the recognition of ATP

Background: Nucleotides are essential molecules in living systems due to their paramount importance in various physiological processes. In the past years, numerous attempts were made to selectively recognize and detect these analytes, especially ATP using small-molecule fluorescent chemosensors. Despite the various solutions, the selective detection of ATP is still challenging due to the structural similarity of various nucleotides. In this paper, we report the conjugation of a uracil nucleobase to the known 4’-dimethylamino-hydroxyflavone fluorophore.Results: The complexation of this scaffold with ATP is already known. The complex is held together by stacking and electrostatic interactions. To achieve multi-point recognition, we designed the uracil-appended version of this probe to include complementary base-pairing interactions. The theoretical calculations revealed the availability of multiple complex structures. The synthesis was performed using click chemistry and the nucleotide recognition properties of the probe were evaluated using fluorescence spectroscopy.Conclusions: The first, uracil-containing fluorescent ATP probe based on a hydroxyflavone fluorophore was synthesized and evaluated. A selective complexation with ATP was observed and a ratiometric response in the excitation spectrum

A Case-Study on the Resolution of the 1-i-Butyl-3-methyl-3-phospholene 1-Oxide via Diastereomeric Complex Formation Using TADDOL Derivatives and via Diastereomeric Coordination Complexes Formed from the Calcium Salts of O,O’-Diaroyl-(2R,3R)-tartaric Acids

The resolution of 1-i-butyl-3-methyl-3-phospholene 1-oxide was studied applying TADDOL [(−)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane], spiro-TADDOL [(−)-(2R,3R)-α,α,α',α'-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol], or the acidic and neutral Ca2+ salts of (−)-O,O’-dibenzoyl- and (−)-O,O’-di-p-toluoyl-(2R,3R)-tartaric acid as the resolving agent. The absolute configuration of the P-asymmetric center was determined by CD spectroscopy and related quantum chemical calculations. In one instance, the single crystal of the diasteromeric complex incorporating i-butyl-3-phospholene oxide and spiro-TADDOL was subjected to X-ray analysis which suggested a feasible hypothesis for the efficiency of the resolution process under discussion that may be an example for the “solvent inhibited” resolution

Crown ether derived from D-glucose as an efficient phase-transfer catalyst for the enantioselective Michael addition of malonates to enones

A monoaza-15-crown-5 lariat ether derived from D-glucose (1) has been applied as chiral phase-transfer catalyst in the Michael addition of diethyl, dimethyl, diisopropyl and dibenzyl malonates to enones under mild conditions to afford the adducts in good to excellent enantioselectivities. In the reaction of diethyl malonate with substituted trans-chalcone, the adducts formed in enantioselectivities up to 89% ee. Among the reactions of substituted diethyl malonates, that of diethyl acetoxymalonate gave the best results (96% ee). The effect of the substituents of the chalcone was also investigated in reaction with diethyl acetoxymalonate. Among the chalcones substituted on the β side, the para-substituted compounds resulted in the highest enantioselectivities (88-97% ee). The substituents on the α-side of chalcone caused a decrease in the enantioselectivity, as compared to the unsubstituted case. The adducts having furyl or thiophenyl substituents were formed with >99% ee. The glucose-based catalyst also proved to be effective in the cases of diisopropyl and dibenzyl acetoxymalonates (including ee-s up to 99% ee). The reactions of diethyl acetoxymalonate with cyclic enones gave the corresponding Michael adducts in enantioselectivities up to 83%. The absolute configuration of one of the new Michael adducts was determined by CD spectroscopy

Supramolecular FRET modulation by pseudorotaxane formation of a ditopic stilbazolium dye and carboxylato-pillar[5]arene

In this paper we introduce a new approach towards the modulation of fluorescence resonance energy transfer (FRET). Two stilbazolium dyes (A, D) exhibiting opposite fluorescence responses upon complexation with anionic, water soluble carboxylato-pillar[5]arene (WP5) were covalently linked via click chemistry, yielding a FRET-capable ditopic indicator (G). The pseudorotaxane formation of G with WP5 in pure water induced fluorescence enhancement combined with the modulation of the FRET process due to the interaction of the macrocycle with the two fluorophore units

Synthesis, Characterization and Application of Platinum(II) Complexes Incorporating Racemic and Optically Active 1-Phenyl-1,2,3,6-Tetrahydrophosphinine Ligand

An efficient resolution method was elaborated for the preparation of (+)-4-chloro-5-methyl-1-phenyl-1,2,3,6-tetrahydrophosphinine oxide using the acidic Ca2+ salt of (–)-O,O-di-p-toluoyl-(2R,3R)-tartaric acid. Crystal structure of the diastereomeric complex was evaluated by single crystal X-ray analysis. Beside this, the absolute P-configuration was also determined by a CD spectroscopic study including theoretical calculations. The tetrahydrophosphinine oxide was then converted to the corresponding platinum complex whose stereostructure was investigated by high level quantum chemical calculations. The Pt-complex was tested as catalyst in the hydroformylation of styrene