Carboxylic fused furans for amino acid fluorescent labelling

Four carboxylic fused furans are presented as new fluorescent labels for the amino and hydroxyl functions of organic molecules. Various representative l-amino acids were chosen as models, labelled at their N-terminus and also at their side-chain. Fluorescent derivatives were obtained in high yields, and their absorption and emission properties were studied.     

A genetically encoded fluorescent amino acid

The fluorescent amino acid l-(7-hydroxycoumarin-4-yl) ethylglycine 1 has been genetically encoded in E. coli in response to the amber TAG codon. Because of its high fluorescence quantum yield, relatively large Stoke's shift, and sensitivity to both pH and polarity, this amino acid should provide a useful probe of protein localization and trafficking, protein conformation changes, and protein-protein interactions.     

Polystyrene-supported triphenylarsine reagents and their use in Suzuki cross-coupling reactions

Soluble and insoluble polystyrene-bound triphenylarsine reagents have been prepared from 4-styryldiphenylarsine. The utility of these reagents as ligands for palladium in Suzuki cross-coupling reactions is demonstrated. In these applications, the use of polymeric triphenylarsine simplifies the purification of the coupled product and allows for the ligand to be recycled. Furthermore, the soluble polymeric arsine reagent permits the palladium catalyst to be recovered and reused.     

Novel light-fluorous TEMPO reagents and their application in oxidation reactions

The synthesis of two light-fluorous TEMPO derivatives is reported, along with their application in oxidation reactions.     

Synthesis and enantioselective fluorescent sensors for amino acid derivatives based on BINOL

Four novel derivatives of 1,1′-bi-2-naphthol have been prepared and the structures of these compounds characterised by IR, MS, ¹H and ¹³C NMR spectroscopy and elemental analysis. The enantioselective recognition of these sensors has been studied by fluorescence titration and ¹H NMR spectroscopy. The sensors exhibited different chiral recognition abilities towards N-Boc-protected amino acid anions and formed 1:1 complexes between the host and the guest. Sensors exhibit excellent enantioselective fluorescent recognition ability towards the amino acid derivatives.     

1-Ethylthio-2,3,3-triarylisoindolinium salts and their reactions with nucleophilic reagents

Stable 1-ethylthioisoindolinium salts were obtained by alkylation of 2-phenyl-3,3-diaryl-1-thiophthalimidines with triethyloxonium tetrafluoroborate. The reactions of these salts with O-, N-, and C-nucleophiles were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 199–202, February, 1987.     

Unnatural amino acid mutagenesis of green fluorescent protein

Unnatural amino acid mutagenesis has been used to selectively substitute tyrosine 66 of green fluorescent protein (GFP) with five novel amino acids: p-amino-L-phenylalanine, p-methoxy-L-phenylalanine, p-iodo-L-phenylalanine, p-bromo-L-phenylalanine, and L-3-(2-naphthyl)alanine. The absorbance and emission maxima of the resulting mutant GFPs span the range from 375 to 435 nm and 428 to 498 nm, respectively. The spectral properties of the mutant GFPs, including the absorbance and fluorescence maxima and quantum yields, correlate with the structural and electronic properties of the substituents on the amino acids.     

Preparation of trifluoromethylated ynamines and their reactions with some electrophilic reagents

N,N-Dialkyl(3,3,3-trifluoro-1-propynyl)amines were prepared by a three-step procedure starting from commercially available 2,2,3,3,3-pentafluoropropanol. The reactions of these trifluoromethylated ynamines with some electrophiles, such as aldehydes, halogens or N-halosuccinimides (NXS), were investigated. The fluorinated ynamines reacted with aldehydes in the presence of a catalytic amount of Lewis acid to provide the corresponding α-(trifluoromethyl)-α,β-unsaturated amides in good to excellent yields with high Z-stereoselectivity. These ynamines reacted with molecular bomine to give, after treatment with sodium hydrogen carbonate, N,N-dialkyl-2-bromo-3,3,3-trifluoropropanamides in good yields. The reaction with an equimolecular amount of NXS in aqueous acetonitrile also gave the corresponding 2-halo-3,3,3-trifluoropropanamides in good to excellent yields. On the other hand, the reaction of the ynamine with NXS in anhydrous acetonitrile led to the formation of the addition products in high yields. Upon treating the addition products with an equimolecular amount of NX′S in aqueous acetonitrile, the corresponding 2,2-dihalo(X,X′)-3,3,3-trifluoropropanamides were produced in nearly quantitative yields.     

Highly enantioselective fluorescent sensor for chiral recognition of amino acid derivatives

A highly enantioselective fluorescent sensor, containing benzylaminomethyl groups at 3,3′-position of 1,1′-bi-2-naphthol (BINOL), has been used to conduct the chiral recognition of α-amino acid derivatives. It is observed that one enantiomer of N-Boc-proline can increase the fluorescence intensity of the binaphthyl fluorophores by over 57-fold, while the other enantiomer can cause only sixfold fluorescence enhancement. Such unusually highly enantioselective response demonstrates that this sensor is potentially useful in the enantioselective recognition of amino acid derivatives.     

Highly enantioselective synthesis of a fluorescent amino acid

A high enantiomeric excess (>99.5%) synthesis of 2-amino-3-(7-methoxy-4-coumaryl) propionic acid ( Amp) is described. The two step synthesis route of this non-proteinogenic amino acid includes an oxazinone derivative as glycine enolate, which is alkylated with the fluorogenic group.     

Chiral nitrone reagents for cycloaddition reactions

The preparation and cycloaddition reactions of new imidazoline nitrones are described. The imidazo[1,2‐b]isoxazole alkene cycloadducts are formed via an exo approach. An example has been tranformed into a pyrrolo[1,2‐a]imidazole as a prelude to a new pyrrolidine synthesis.     

Design of active-site-directed fluorescent probes and their reactions with biopolymers

Fluorescent probes which are active-site-directed, reversible, competitive inhibitors of serum cholinesterase (ChE) enzymes have been designed and synthesized. Reversible inhibitors of enzyme active sites have a unique importance when they act as fluorescent probes, allowing fluorescence spectroscopic detection of conformation changes and activesite dynamics. 5-Dimethylamino-naphthalene-1-sulfonamido-N,N-dimethyl-n-propyl-amine and its aliphatic quaternary derivative are fluorescent probes for serum cholinesterase. The quaternary probe forms complexes with acetylcholinesterase (AChE). The dissociation constants K_d for the two probes with serum ChE are 6.0 × 10^?7 and 6.5 × 10^?7M. The inhibition constants K_i are 3.1 × 10^?6 and 6.3 × 10^?6M from the slopes of Lineweaver-Burk plots. The Michelis constant K_m for the enzyme was 8.8 × 10^?4M.     

Novel chiral fluorescent macrocyclic receptors: synthesis and recognition for amino acid anions

New chiral fluorescence macrocycles 1 and 2 containing naphthalene and amino acid units were synthesized. The binding properties for amino acid anions were examined by the fluorescence and ¹H NMR spectra. The results indicated good enantioselectivity of 1 toward the N-protected phenylalanine anions.     

New chromogenic reagents for labelling amino groups in peptides. Chromatographic and preparatives aspects

Summary A new type of chromogenic reagent for labelling the amino groups of peptides or amino acids, 5-substituted 2,4-dinitrofluorobenzenes, is presented. These reagents are characterized by a polarity determined by the function included in the substituent in the 5-position and by the nature of this substituent. Preparation and chromatographic behaviour of these reagents, of eventual by-products of reactions and of some N-(2,4-dinitro-5-diethylaminophenyl)-peptides or amino acids are described.Proportions in solvent mixtures are v/v except otherwise indicated. Abbreviations: lit=literature, TLC=thin-layer chromatography, TLE=TL electrophoresis, see also: Figs. 2, 3, 5.     

Chiral N-phosphonyl imine chemistry: new reagents and their applications for asymmetric reactions

Novel chiral N-phosphonyl imines 2 have been designed and synthesized using chiral N-phosphoramide 1. These N-phosphonyl imines have been successfully utilized for asymmetric aza-Darzens reaction and asymmetric aza-Henry reaction. The C₂-symmetric chiral auxiliary tolerates oxidation, is not sensitive to racemization and can be recycled for large scale synthesis.     

Building addressable libraries: amino acid derived fluorescent linkers

A new amino acid derived fluorescent linker for attaching molecules to the surface of a microelectrode array has been developed. Molecules to be monitored on an array are attached to the C-terminus of the linker, the N-terminus is then used to attach the linker to the array, and the side chain is used to synthesize a fluorescent tag. The fluorescent group is made with a one-step oxidative cycloaddition reaction starting from a hydroxyindole group. The linker is compatible with site-selective Cu(I)-chemistry on the array, it allows for quality control assessment of the array itself, and it is compatible with the electrochemical impedance experiments used to monitor binding events on the surface of the array.     

Derivatives ofβ- chlorosulfenylcarboxylic acids and their reactions with nucleophilic reagents

Russian Chemical Bulletin -     

A new environment-sensitive fluorescent amino acid for Fmoc-based solid phase peptide synthesis

A new 4-(N,N-dimethylamino) phthalimide-based environment-sensitive fluorescent building block for solid phase peptide synthesis, has been synthesized and incorporated into peptides. Peptides incorporating this residue show great potential for biological applications in sensing protein/protein interactions.