| Abstract: | The 13C NMR spectra of leonurine hydrochloride and thirteen of its analogues in DMSO-d6 have been analyzed. Changes in the aromatic substituents have no significant effect on the chemical shifts of the side chain methylene carbons indicating that they do not influence the conformation of the latter. Observed deviations from additivity of substituent effects for the methylene carbon chemical shifts suggest that the methylene side chains of these compounds may be more tightly coiled than are the corresponding n-alkanes. In representative cases no change in conformation is evident in 50% aqueous DMSO-d6 solutions, indicating that similar considerations may apply in aqueous media. |
