Configurational and conformational analysis

The alkaloids of Lycopodium cernuum L. II. The stereochemistry of cernuine and lycocernuine

“…), whereas irradiation a t T 8.12 (presumably the C-11 methylene) causes it to collapse to a doublet (splitting 2.1 c.p.s.). This result demonstrates the equatorial nature of the proton geminal to the hydroxyl group (2,3), and thus the axial nature of the hydroxyl group. The ease of elimination of the C-12 substituent (1) is in accord with this assignment.…”

A Proton Magnetic Resonance Study of the Stereochemistry of the Methylaspartate Ammonia-Lyase Reaction*

“…Perhaps it is significant that all the systems studied by Williamson were of the ABX type and our ABX values are reasonably close to his. However, in a recent exhaustive review of vicinalcoupling constants in substituted cyclohexanes (Huitric et al, 1963) no such simple dependence on electronegativity was observed. The variations in gauche and trans couplings could not be satisfactorily explained either on the basis of changes in bond angle or substituent electronegativity.…”

NMR Conformational analysis of 4-hydroxycyclohexanone and 1,4-cyclohexanediols. Coupling constants averaging induced by conformational equilibria and by strong coupling effects—role of solvent

“…and 3.5 c.P.s., respectively (11,12), providing that ( P B -P A ) is large with respect to JAB As the ratio ( P B -P A ) / J A B -P 0, strong coupling effects become operative and J X A and JXB tend to average out. In the limit where P B = P A , the signal of the X proton will appear as a symmetrical pentuplet with line separations equal to ( J X A + J x B ) /~, about 5 c.P.s., and the combined signals of the A and B protons will give a doublet with the same separation of about 5 C.P.S.…”