ISOMERIC NICOTINES - THEIR SOLUTION CONFORMATION AND PROTON, DEUTERIUM, C-13, AND N-15 NUCLEAR MAGNETIC-RESONANCE

Complete 1H, 13C, and 15N assignments are presented for 2-nicotine (2) and 4-nicotine (4) as well as 2H assignments of selectively deuterated 2 and 4 derivatives. The 2H chemical shifts of the deuterated derivatives allow assignment of XH resonances to specific protons and provide starting chemical shifts for analysis of the severely overlapping pyrrolidine resonances. The three-, four-, and five-spin pyrrolidine 3H spectra of these analogues are less complex to analyze than the corresponding seven-spin spectra of 2 and 4. The Karplus parameters obtained from the lH analyses indicate an envelope conformation for both 2 and 4. Analysis of the long-range coupling constants between H(2) and the pyridine protons suggests a perpendicular spatial arrangement of the pyridine and pyrrolidine rings for both 2 and 4. A comparison is made between the solution conformations of 2 and 4 and the conformation of 3-nicotine (3). © 1979, American Chemical Society. All rights reserved.