A cleft type receptor which combines an oxyanion hole with electrostatic interactions.

A receptor for carboxylic acids which combines an oxyanion-hole structure with electrostatic forces has been prepared. X-ray diffraction studies have been carried out to evaluate the geometry of both the free receptor and its associated species with several carboxylic acids and many different arrangements have been discovered for the H-bond pattern in the associated species.

A molecular receptor selective for zwitterionic alanine.

A molecular receptor has been synthesized joining an aza-crown ether with a chiral chromane which mimics the oxyanion hole of the enzymes. With this receptor an apolar host-guest complex with zwitterionic alanine has been achieved through the formation of up to seven H-bonds. This complex allows the extraction of aqueous alanine to a chloroform phase, while other natural amino acids are poorly extracted or are not extracted at all. Due to the chiral nature of the receptor, enantioselective extraction from the aqueous alanine solution to a chloroform phase takes place. X-Ray analysis combined with anisotropic effects, NOE and CD studies revealed the absolute configuration of both strong and weak complexes. Modelling studies also support the proposed structures. The presence of an oxyanion-hole motif in this structure was corroborated by X-ray diffraction studies.

A bio-inspired enantioselective small-molecule artificial receptor for ß adrenergic agonists and antagonists and its application for enantioselective extraction.

Administration of enantiomerically pure ß-adrenergic agonists and antagonists increases their activity and reduces side effects. We report here a small-molecule artificial receptor (SMAR) that, by mimicking the ß-adrenergic receptor, is able to enantioselectively extract commercial ß-adrenergic interacting drugs. The selectivity is justified according to DFT calculations and X-ray diffraction experiments.

A molecular receptor for zwitterionic phenylalanine.

The combination of a 1,3-ketoenol system and two pyridine molecules attached as sulfonamide and carboxamide to a benzofuran skeleton allows the preparation of a novel chiral receptor for zwitterionic phenylalanine association. Interestingly, no crown-ether, urea or guanidinium are necessary to carry out the extraction of amino acids from the aqueous solution, which constitutes a breakthrough in comparison with other receptors for zwitterionic amino acid extraction.

A highly selective receptor for zwitterionic proline.

A chiral chromane receptor has been synthesized which mimics the oxyanion hole of the enzymes. In this receptor H-bonds and cation-π interactions team up to generate an apolar host-guest complex with zwitterionic proline. This complex allows the extraction of only proline to a chloroform phase, while no other natural amino acids are extracted. Due to the chiral nature of the receptor, enantioselective extraction from the aqueous proline solution to a chloroform phase takes place. L-Proline provided an easy method to resolve the receptor racemic mixture, while anisotropic effects, NOE and CD studies revealed the absolute configuration of the receptor. Modelling studies also support the proposed structures. The presence of an oxyanion-hole motif in this structure was corroborated by X-ray diffraction studies.

Chiral recognition with a benzofuran receptor that mimics an oxyanion hole.

A new chiral benzofuran receptor has been synthesized and its properties in the association of amino acid derivatives have been studied. X-ray structures were obtained and these corroborate the presence of an oxyanion-hole motif in these structures.

4,5-Dibromo-2,7-di-tert-butyl-9,9-dimethyl-9H-thioxanthene.

In the title compound, C(23)H(28)Br(2)S, the thioxanthene unit is twisted, showing a dihedral angle of 29.3 (5)° between the benzene rings. When projected along [001], the packing shows two types of channels. The crystal studied was a racemic twin.