Versatile and Practical Chiral Shift Reagent with Hydrogen-Bond Donor/Acceptor Sites in a Macrocyclic Cavity

Abstract

[structure: see text] Bifunctional macrocycle 1 with C2 symmetry was newly synthesized. NMR studies demonstrated that receptor 1 functions as a chiral shift reagent (solvating agent) that is highly effective for a wide range of chiral compounds having a carboxylic acid, oxazolidinone, lactone, alcohol, sulfoxide, sulfoximine, isocyanate, or epoxide functionality. Binding constants were determined to investigate the binding behavior of 1.

Spectroscopic Discrimination of Diastereomeric Complexes Involving an Axially Chiral Receptor

“…Enantiomerically pure M aR was synthesized and purified according to established procedures . The pure enantiomers P D / P L and D D / D L were purchased from a commercial source and used without further purification.…”

“…Enantiomerically pure M aR was synthesized and purified according to established procedures. [36,37] The pure enantiomers P D /P L and D D /D L were purchased from acommercial source and used without further purification. The proton-bound complexes were generated in am odified Bruker Esquire 6000 quadrupole ion trap by ESI of equimolar mixtures of macrocycle M aR and the corresponding amino acid (10 À5 m)i np ure methanol.…”

Silicon-Containing GABA Derivatives, Silagaba Compounds, as Orally Effective Agents for Treating Neuropathic Pain without Central-Nervous-System-Related Side Effects

“…Optical resolution of the racemic cyanobutanoate ester was achieved by enzymatic hydrolysis with Novozyme 435 (Sigma-Aldrich) in 0.1 M phosphate buffer (pH 7.4)/dimethyl sulfoxide (5:1) to obtain optically active carboxylic acid ( R -rich) and recovered ester ( S -rich). 28 The enantiomeric ratios, estimated from the 1 H NMR spectra in the presence of a chiral shift reagent Chirabite-AR (Tokyo Chemical Industry Co., Japan), 29 were 5:1–9:1 when the extent of enzymatic hydrolysis reached about a half. To achieve high optical purity (at least 96% ee), the carboxylic acid was re-esterified, and the resulting R -rich ester as well as S -rich ester were both rehydrolyzed with Novozyme, if necessary.…”

Asymmetric Azamacrocycles as Chiral Solvating Agents

“…Chiral macrocycle 1 (Scheme 12.1) with a C 2 symmetric BINOL unit was found to be an extremely versatile CSA for a wide range of chiral compounds such as carboxylic acids, oxazolidinones, carbonates, lactones, alcohols, sulfoxides, sulfoximides, isocyanates, and epoxides [11]. 1 H-NMR signals for the enantiomers of 3, 4, and 5-13 (Scheme 12.2) were well split upon complexation with the chiral macrocycle 1a.…”