Conformational Analysis of Verbenols and Related Alcohols by PMR Spectra with a Chemical Shift Reagent

Abstract

The conformation of cis- and trans-verbenol and five pairs of cis-trans alcohols having a 6,6-dimethylbicyclo[3.1.1]heptane skeleton was analyzed using the PMR spectra under the influence of the chemical shift reagent, Eu(dpm)₃. In most of such spectra, different proton signals appeared separately, and decoupling treatment in addition to direct analysis of the coupling constants of the separated signals enabled us to elucidate the conformation of the alcohols. The alcohols having a double bond took a “Y-shape”. The other alcohols were shown to be the “bridged boat” or “bridged chair” conformation in which the secondary methyl group exists always as a quasiequatorial.