A Computational Investigation of the 15N Chemical Shift Behavior of Strychnos Alkaloids

Members of the broad family of Strychnos alkaloids have been the favorite molecules for the development and evaluation of new NMR methods for many years, including the establishment of the 1H-15N two-dimensional NMR methods. The present study is an effort to computationally evaluate the 15N chemical shift behavior of eight members of this structurally diverse group of indole alkaloids. The molecules range from relatively “simple” strychnine and brucine and their respective N-oxides to molecules as complex as vinorelbine, a synthetic analog used in cancer chemotherapy, and sungucine, a naturally occurring complex dimeric member of the family. The 20 15N chemical shifts in this study afforded a CMAE of 2.96 ppm and an RMSD of 3.50 ppm, with the data affording a correlation coefficient, r = 0.997.