Terpenoids. Part IV. The nuclear magnetic resonance properties of the stereoisomeric ent-kauran-15-ols and 13β-kauran-15-ols

Abstract

The J_15,16 values for the stereoisomeric ent-kauran- and 13β-kauran-15-ols indicate a twist envelope conformation for ring D in all except the (16S)-15β-ols. The chemical shifts of the C-15 protons confirm the stereochemical assignments. Calculations of the difference in chemical shift of the C-15 protons in isomeric pairs of these alcohols are not sufficiently accurate to distinguish between envelope and twist envelope conformations of ring D.