Synthesis of optically active 2-methylchroman derivatives and application to chiral dopants for nematic liquid crystals

Chiral 2-methylchroman-2-carboxylic acid derivatives were prepared as new chiral dopants for nematic liquid crystals. The starting material, optically active 6-benzyloxy-2-methylchroman-2-carboxylic acid, was newly synthesized as a rigid core structure and resolved by a diastereomeric salt formation method. Its absolute configuration was determined by comparing its circular dichroism spectrum with that of the commercially available (S)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid derivative. The helical twisting power of the new dopants was determined and the relationship between their functional groups and flexible terminal structures was studied.