Prochiral and Chiral Resolution in ²H NMR Spectra: Solutes in Stretched and Compressed Gelatin Gels

We demonstrate prochiral and chiral spectral resolution using residual 2H NMR quadrupolar splittings over a wide range of anisotropic conditions in liquid samples. We use a reversible gel-stretching/compressing device in a conventional high-field NMR spectrometer. We show the stability of gelatin gels as well as their unique ability to switch between multiple stretched and compressed states, thus also changing the sign of residual dipolar couplings in 1H and 13C NMR. This flexibility will be important for resolving spectra of mixtures of other chiral compounds and for structure determination of selected peptides

NMR Spectra of Glycine Isotopomers in Anisotropic Media: Subtle Chiral Interactions

NMR spectra of deuterated glycine-2-¹³C revealed interactions between chiral anisotropic gelatin and κ-carrageenan gels and the prochiral and chiral isotopomers. The ¹H, ²H and ¹³C NMR spectra of mixtures of racemic mono- and prochiral bis-deuterated glycine-2-¹³C were resolved and well simulated using distinct dipolar coupling constants <i>D</i>_CαH and <i>D</i>_CαD for the enantiomers and also for the -¹³C_αD₂- group (<i>D</i>_C,DA, and <i>D</i>_C,DB). The orientation of the proton or deuteron on the ¹³C_α-atom of glycine was assigned by analogy with alanine and lactate assuming that the molecular orientation of glycine isotopomers is the same. The assignment of the prochiral sites was derived from chiral analogues

Synthesis and Characterization of a Disulfide-Linked <i>C</i>₅-Symmetric [5]Carceplex

The synthesis and characterization of the first disulfide-linked and C5-symmetric carceplex·(guests)2 using the recently described [5]cavitands as building blocks is reported. The solution behavior of the new carceplexes was explored by 1D NOSEY (EXSY) experiments. The disulfides have unusually high energy barriers to interconversion due to their cooperativity. The guests (2 DMF or 2 DMA) reside in an unusual orientation in parallel planes that are perpendicular to the principal axis of the host