Efficient Recognition of Chiral Carbamoyl‐α‐Hydroxyacids with a Cleft‐Type Receptor

Abstract

gen bonds with an a-functionalized carboxylic acid as the guest 6 , = 5.21 6,, = 0.69 / ( 9 -5 (4-1 P.

Large Increase in Cation Binding Affinity of Artificial Cyclopeptide Receptors by an Allosteric Effect

“…Knowing the cation−crown ether 2 −tosylate stability constants, we were able to determine the K a of the corresponding BTMA + complex by an alternative method, namely by competitive NMR titrations . For this, increasing amounts of BTMA + iodide were added to solutions of, e.g., K + −18-crown-6 2 −tosylate in CDCl 3 .…”

“…In all dilution titrations, the dissociation of the cationcrown ether complexes at low concentrations was taken into (18) Molecular modeling was performed on a Silicon Graphics workstation using the program Cerius 2 (Molecular Simulations Inc.) with a Dreiding 2. 21 account by including the corresponding stability constants 20 in the calculations. With Li + and 12-crown-4, the upfield shift upon complexation by 2-tosylate was not large enough to be followed quantitatively.…”

“…Knowing the cation-crown ether 2-tosylate stability constants, we were able to determine the K a of the corresponding BTMA + complex by an alternative method, namely by competitive NMR titrations. 21 For this, increasing amounts of BTMA + iodide were added to solutions of, e.g., K + -18-crown-6 2-tosylate in CDCl 3 . Under these conditions, complexes of 2-tosylate with BTMA + and the cation-crown ether are formed simultaneously in relative amounts that depend on the ratio of their association constants.…”

Enantioselective recognition of α-amino acid derivatives with a cis-tetrahydrobenzoxanthene receptorElectronic supplementary information (ESI) available: binding data. See http://www.rsc.org/suppdata/p2/b2/b203054c/

“…These promising results suggested that it might be possible to resolve a racemic mixture of host 2, using its supramolecular properties. 3 Ethoxycarbonyl--leucine was selected as the guest due to its lack of UV absorption at 250 nm. Preparative TLCs were impregnated with a 2% amino acid solution in chloroform, dried and loaded with host 2 (50 mg); elution with CH 2 Cl 2 resulted in two different bands (R f = 0.72, R f = 0.23) for each of host 2 enantiomers.…”

Techniques in Preparative Chiral Separations

“…Very high values of enantioselectivity can be attained with specific selectors for particular enantiomers [182,[201][202][203][204]. Nevertheless, the application domain is reduced consequently.…”