Hydrogen bonding pattern in N-benzoyl(-dl-)-l-phenylalanines as revealed by solid-state NMR spectroscopy

X‐ray and 13C solid‐state NMR studies of N‐benzoyl‐phenylalanine

“…In this work, the spatial proximity of a heterogeneous material (sample 2 ) was analyzed using the ODESSA technique, employing sample selectively, 13 C enriched at carboxyl group. The accuracy of the method was confirmed by inspection of the data for sample 1 and other model compounds reported elsewhere (28,29). Finally, it can be concluded that ODESSA is a very useful and prospective approach in structural studies of biological samples.…”

“…If the protons are coupled strongly to each other a weak collision approximation is valid and the term F ij (0) is given by zero quantum relaxation time constant T 2 (ZQ) , which is often approximated from the sum of the single‐quantum relaxation times of the two spins. As revealed by employing few model compounds, W ij parameters provide a route to structural information on single‐labeled molecules (28,29). In fact, it has been shown that the ODESSA method can recognize intermolecular distances between chemically equivalent 13 C nuclei up to 9 Å.…”

“…However, by using the ODESSA method, we are in position to distinguish ‘further’ and ‘nearest’ neighbors if W ij decay is different for each modification. This may be done easily by using proton decoupling during the mixing time τ m , which makes the process of spin exchange considerably more efficient (28,29). Consequently, when the rate of spin diffusion for all centers is similar or the same, we can conclude that the distances between nuclei are comparable.…”

“…We have shown very recently the possibility of measuring internuclear distances between chemically equivalent nuclei (28,29) using 1D exchange spectroscopy by sidebands alternation (ODESSA) (30,31). Here, we demonstrate the usefulness of this approach for the analysis of spatial proximity in heterogeneous domain for polycrystalline sample 2 .…”

What High‐Resolution Solid‐State NMR Spectroscopy Can Offer to Organic Chemists

“…A two-dimensional radio frequency driven (RFDR) dipolar recoupling spin-exchange experiment with a spinning speed up to 26 kHz on uniformly labeled aspartame gave complimentary assignments for short-and long-range interactions. [24,25] Figure 3 (see a and b) present the 13 C CP/MAS spectra of models selectively 13 C-labeled at the carboxyl position. [23] Small peptides and their derivatives are useful models in research of polymorphism in natural products.…”