Proton NMR assignments for R,S‐1,1′‐binaphthol (BN) and R,S‐1,1′‐binaphthyl‐2,2′‐diyl hydrogen phosphate (BNDHP) interacting with bile salt micelles

Abstract

We report proton chemical shifts for two model chiral analytes that are commonly used in the study of micellar electrokinetic capillary chromatography (MEKC), R,S-1,1'-binaphthol (1, BN) and R,S-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (2, BNDHP), in the absence and presence of monomers and micelles of sodium cholate and sodium deoxycholate. The analytes undergo fast exchange in and out of the micelles, which perturbs the analytes' chemical shifts, and which we use to resolve some resonances that are degenerate at both 300 and 600 MHz. Although BN and BNDHP are simple molecules, the proton assignments are only unambiguously established with the aid of the exchange with micelles, an attractive alternative to other methodologies such as the use of paramagnetic shift reagents which may also cause spectral distortions. We rely also upon 2D-NOE spectra of samples in the presence of micelles to perform these assignments. Recently published assignments, which were based upon 2D-COSY spectroscopy, appear to be in error and are corrected here. Finally, we note that these shifts are information-rich reporters on the nature of the interactions of these model analytes with the micelles.

Sodium Cholate Aggregation and Chiral Recognition of the Probe Molecule (R,S)-1,1′-Binaphthyl-2,2′-diylhydrogenphosphate (BNDHP) Observed by 1H and 31P NMR Spectroscopy

“…The 1 H shifts of BNDHP are also well resolved, so that it is possible to obtain distinct cholate dependent changes of individual BNDHP proton chemical shifts in order to gain localized information. Assignments are indicated on Figure 5 and have been previously described21.…”

Water‐soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds

“…Chiral, water-soluble micelles have been reported, but these systems have not been widely studied in NMR applications. [11][12][13] The most useful water-soluble, chiral NMR reagents are cavity compounds. The interior of the cavity is often hydrophobic, such that the hydrophobic portion of organic salts is stabilized by insertion into the cavity in water.…”

Bile Salts in Chiral Micellar Electrokinetic Chromatography: 2000–2020

“…These were called the primary and the secondary micelles. This was confirmed by Rovnyak and co-workers in a series of four papers using data gathered from MEKC and proton nuclear magnetic resonance spectroscopy ( 1 H NMR) [ 16 , 17 , 32 , 33 ]. They used R,S -binaphthyl-1,1′-diylhydrogenphosphate as an analyte.…”