Synthetic studies towards the anti-inflammatory agent, oleocanthal using a Johnson–Claisen (orthoester) rearrangement strategy

Abstract

The phenol catalysed Johnson orthoester-Claisen rearrangement of allylic alcohol (1R)-6, proceeds via two possible ketene-acetal transition states TS-1 and TS-2, to afford a 1:10 mixture of diastereomers. The transition state configuration of the C-1 methyl group (axial or equatorial) is proposed to be the dominating factor dictating whether the sigmatropic rearrangement takes place from the convex or concave face of the starting material.