Novel nor-sesquiterpenoids in New Zealand honeys: the relative and absolute stereochemistry of the kamahines, an extension of the Mosher method to hemiacetals

A comparative study of the NMR data of kamahine A and B acetates with those of kamahine E acetate helps determine the relative stereochemistries of the diasteroisomeric kamahines A and B, novel non-sesquiterpenoids in New Zealand honeys. NMR and molecular modeling of diastereoisomeric hemiacetal methoxymandelate esters help establish the absolute configurations of the kamahines. Mosher-Trost model efficiently predicts the absolute by considering the positive torsion angle between methine hydrogen and carbonyl of hemiacetate mandelate esters.