Methyl esters of four common bile acids, 3a-hydroxy-5gcholan-24-oic (lithocholic) acid, 3a,7a-dihydroxy-5~ cholan-24-oic (chenodeoxycholic) acid, 3a,l2udihydroxy-5~holan-24-oic (deoxycholic) acid and 3a,7a,lZatrihydroxy-5&cholan-24-oic (cholic) acid, and 14 acetylated, trifluoroacetylated, mesylated and 0x0 derivatives of methyl 5gcholan-24-oates were prepared and their "0 NMR spectra recorded. In spite of their relatively high molecular masses and the rigid molecular structure of the steroid skeleton, most of the oxygens included in these structures gave well resolved '"0 NMR resonance lines at natural abundance in 0.25-0.5 M acetonitrile solutions at 75OC. In agreement with the present ''0 NMR results, molecular mechanics calculations revealed that a hydroxy substituent located at the &-position clearly differs from the hydroxyls at the 7a-and 12u-positiom. This is due to the fact that the 3u-hydroxyl possessing only two y-carbons at antiperiplanar positions is less shielded than the other hydroxyls influenced also by the shielding effects of 'y-guuche carbons. The spectral deconvolution of the overlapping signals of the 7a-and 12a-bydroxyls is based on a computer-aided method or on chemical substitutions. The 0x0 groups located at the longitudinal (foxo) vs. transversal (7-and 120x0) axes of the steroid framework show very different quadrupolar relaxation properties and '"0 NMR linewidths owing to the strong anisotropy of overall molecular motion. In contrast, the I7O NMR linewidths of all 3a-, 7a-and 12a-hydroxyls are very similar and clearly smaller than those of the corresponding 0x0 groups, revealing that their quadrupolar relaxation is merely determined by their internal rotation rather than by the overall molecular motion.

The 13C NMR spectra were recorded and assigned for nine derivatives of methyl 5β‐cholan‐24‐oates (esters of bile acids) including hydroxy, oxo and/or acetyloxy groups. Assignments were based on the empirical substituent‐induced chemical shifts (SCS), spectral comparison with compounds of similar structure, distortionless enhancement by polarization transfer (DEPT) and proton coupled 13C NMR measurements.