Carbon-13 NMR of crystalline morphine

Conformational analogies of morphine agonists and antagonists as revealed by carbon‐13 NMR spectroscopy

“…The unwarranted equating of free alkaloid bases with their salts in conformational studies occurs elsewhere in the literature. 18 It must be pointed out that a full extrapolation of the above solution conformation data to conformation at the receptor is not possible at present, as neither the detailed topography of the opiate receptor nor the exact mode of interaction of the opiates with the opiate receptor are known.3 However, we believe that our results provide a basis for further study of the factors responsible for differentiating the agonists and antagonists at the receptor.…”

13C and 31P high resolution solid state NMR studies of cyclophosphamide and its analogues

“…4. Most of these resonances are singlets but some of them are broadened and split by 13 C-14 N dipole-dipole coupling [24,25]. We used the two-dimensional phase-adjusted spinning sidebands (2D PASS) experiment [26,27] with the aim of correctly analyzing these spectra.…”

General theoretical formalism for describing the high-order effects of the dipolar coupling between spin-1/2 and quadrupole nuclei

“…1 When MAS is used, the problem is time dependent, and certain procedures must be invoked such as the adiabatic approximation. [16][17][18][19][20] On the other hand, Olivieri et al, [21][22][23] and Gan and Grant, 24 obtained some approximate analytical solutions based on a perturbation expansion. These analytical solutions are useful for the evaluation of spectral line broadening and splitting as long as the particular perturbation treatment is valid.…”

“…For static samples, this treatment is satisfactory but for spinning samples, it requires modification and a timeordering calculation or additional assumptions must be introduced to permit spectral simulations. Strikingly, most previous studies [11][12][13][14][15][16][17][18][19][20][21][22][23][24] did not include any time-ordering calculation. Moreover, contrary to other NMR researches, previous lineshape studies did not use the density matrix formalism, instead, all discussions were carried out in terms of wave functions and the Schrödinger equation.…”