Conformational Studies of Marine Polyhalogenated ?-Chamigrenes Using Temperature-Dependent NMR Spectra. Cyclohexene-ring flipping and rigid-chair cyclohexane ring in the presence of equatorial halogen atoms at C(8) and C(9)
obtained by hydride reduction of (+)-12, behave similarly, with slow half-chair inversion of the cyclohexenol ring. In each case, both conformers are about equally populated and detectable by NMR, except in the case of (+)-15, where repulsive interactions between BrC(2) and Heq−C(7) make the population of the conformer 15b with Me—C(5) faced to Hax−C(10) so low that it escapes direct 1H-NMR detection. The