Dimerization of ferulic acid and structure determination of phenylindane derivatives

Ferulic acid dimers with phenylindane skeletons were obtained from ferulic acid 1 in an acidic ethanol solution. The reaction conditions used to prepare the dimers or the ester were examined in detail, and the stereochemistries of the dimers were determined. The structural features of the dimers and the diastereoselective formation mechanisms involved in forming the two types of dimers (the racemic diastereomer 8α, which was a major product, and the racemic diastereomer 8γ, which was a minor product) were characterized.