Pattern-based recognition of heparin contaminants by an array of self-assembling fluorescent receptors.

Tracking down potential killers: Strong host-guest interactions enable the facile combination of polycationic cyclodextrin binding motifs (blue) with fluorescent reporters (orange) tethered to a hydrophobic guest molecule (dark green). An array of supramolecular fluorescent receptors prepared by this modular approach was used for the pattern-based recognition of negatively charged contaminants in the anticoagulant drug heparin.

Remarkably stable inclusion complexes with heptakis-[6-deoxy-6-(2-aminoethylsulfanyl)]-beta-cyclodextrin.

Complexes of heptakis-[6-deoxy-6-(2-aminoethylsulfanyl)]-beta-cyclodextrin (1) and a series of common cyclodextrin guests were studied by NMR, fluorescence spectroscopy, and ITC experiments. NMR conformational analysis shows that the thioethers of 1 are positioned over the hydrophobic cavity of the cyclodextrin, increasing potential hydrophobic interactions with guest molecules. The combination of the increased hydrophobic character, the electrostatic complementarity and a hypothesized conformational change in 1 lead to a complex with the dye 2,6-ANS (5) that is over 2000 times more stable than with the native beta-cyclodextrin. One of the most stable host-guest complexes between a cyclodextrin and a small molecule measured to date was revealed between 1 and lithocholic acid (4) with an association constant of 5.5 x 10(7) M(-1).

An astrophysically-relevant mechanism for amino acid enantiomer enrichment.

The sublimation of low ee amino acids was examined while exploring simple mechanisms by which high ee amino acids can be generated under conditions that exist in space; significant enantioenrichment of a variety of amino acids by sublimation was achieved.

Synthesis of solution-phase phosphoramidite and phosphite ligand libraries and their in situ screening in the rhodium-catalyzed asymmetric addition of arylboronic acids.

Herein, we report the automated parallel synthesis of solution-phase libraries of phosphoramidite ligands for the development of enantioselective catalysts. The ligand libraries are screened in situ in the asymmetric rhodium-catalyzed addition of arylboronic acids to aldehydes and imines. It is shown that the described methodology results in the straightforward discovery of leads for highly efficient enantioselective catalysts.

Enantioselective rhodium-catalyzed addition of arylboronic acids to trifluoromethyl ketones.

The catalytic asymmetric 1,2-addition of a series of arylboronic acids to 2,2,2-trifluoroacetophenones is described with high isolated yields (up to 96%) and good enantioselectivities (up to 83% ee) using a rhodium(I)/phosphoramidite catalyst.

Rhodium-catalyzed addition of arylboronic acids to isatins: an entry to diversity in 3-aryl-3-hydroxyoxindoles.

[reaction: see text] A general method for the catalytic 1,2-addition of aryl and alkenyl boronic acids to isatins is described using a rhodium(I)/triphenylphosphite catalyst. The application of this transformation allows the synthesis of a variety of 3-aryl-3-hydroxyoxindole building blocks in high yields. An enantioselective version of this reaction using a rhodium(I)/phosphoramidite system is also presented.

Rhodium/phosphoramidite-catalyzed asymmetric arylation of aldehydes with arylboronic acids.

Phosphoramidites are effective chiral ligands in the rhodium catalyzed addition of arylboronic acids to aldehydes providing up to 75% enantioselectivity and up to 96% isolated yield.

Enantioselective synthesis of 2-aryl-4-piperidones via rhodium/phosphoramidite-catalyzed conjugate addition of arylboroxines.

[reaction: see text] The highly enantioselective synthesis of 2-aryl-4-piperidones by rhodium/phosphoramidite-catalyzed conjugate addition of arylboroxines to 2,3-dihydro-4-pyridones is described. Both enantiomers of a variety of products with sterically and electronically different R substituents were obtained in high isolated yield and with excellent enantioselectivity up to 99%.