摘要:
A practical asymmetric synthesis of (S)-cyclohexylphenyl glycolic acid has been demonstrated at pilot scale. The key step is the asymmetric aldol reaction using the Seebach approach of self-replication of stereochemistry. (S)-Mandelic acid was converted into (2S,5S)-3 in >99/1 diastereomeric ratio. The dioxolone (2S,5S)-3 was then subjected to aldol conditions to give the aldol intermediate (2S,5R)-5 in 91% yield with >99.5/0.5 diastereomeric ratio. The aldol product was converted to the desired hydroxy acid. (S)-CHPGA, in three steps with only one isolation in high yield (95%) and high purity. (C) 200 Elsevier Ltd. All rights reserved.