Abstract
Bile salts are synthesized by all classes of vertebrates [1] and enable the digestion of lipophilic nutrients. [2] Their amphipathic character facilitates their aggregation to micelles and enables them to transport lipid soluble mol- ecules in the gastrointestinal tract. [3] Bile salts differ in their structure due to the presence and orientation of hydroxyl groups, the length and level of unsaturation of their carbon side chain, and the substituent of its termi- nal carbon atom, which divides them into bile acids and bile alcohols. These structural differences allow a lot of variation in bile salts across vertebrates but also on the level of orders, as described for fish. Some bile salts are even unique to certain fish orders as 5α‐cyprinol is for the order of Cypriniformes. [4] 5α‐Cyprinol sulfate (1, Figure 1) has earlier been identified as a constituent of bile in fish species. [5,6] Although bile salts have attracted considerable inter- est, analytical methods mostly employed for the identification of 5α ‐cyprinol sulfate have been spectrometric techniques, while structural elucidation attempts by NMR for this compound have been scarce so far. One of the reasons is the usually low concentration of the available samples. Therefore, only a very few references in the scientific literature contain NMR data for this molecule, [5–7] all of them with limitations in terms of incom- plete assignment and low resolution of 2D spectra, which to the best of our knowledge did not permit a full assignment of the proposed structure by means of NMR until now. Furthermore, some of the chemical shifts, especially in the only complete 13C assignment that is currently available, seemed to be rather questionable. [5] When confronted with the structure verification by NMR, we therefore decided to revise the formerly published assignments. Hereby, it was our intention to confirm or correct the assignment of 1H and 13C resonances. However, we did not attempt to fully analyze the J‐coupling network for protons to derive any further conformational clue besides the one we could deduce from NOE experiments. Because only recently, magnetic resonance in chemistry announced a change in its s ubmission etiquette for NMR assignments, [8] we were concerned to complete the aforementioned task bearing in mind the future reusability and readability of electronic NMR data information. [9] Thus, the present letter includes in addition to our description of structure verification and assignment revision all NMR spectroscopy material in the fully machine readable, recently published NMReDATA format for small molecule's assignments.
Hahn, M