Synthesis of (S)-ricinoleic acid and its methyl ester with the participation of ionic liquid

•Synthesis of (S)-ricinoleic acid in large scale.•Confirmation of enantiopurity of natural ricinoleic acid by GC.•Utilization of the ionic liquid to the key-step process of configuration inversion.

(R)-Ricinoleic acid methyl ester obtained from commercial castor oil was transformed in a three-step procedure into its S-enantiomer in overall 36% yield using ionic liquid (1-butyl-3-methylimidazolium acetate) in the key step process. The developed procedure provides easy access to (S)-ricinoleic acid and its methyl ester of over 95% enantiomeric excess. Optical rotations of the newly obtained compounds as well as their chromatographic and spectral characteristics are provided and discussed in the context of enantiopurity both of the substrate material and the final products.

Graphical abstractTransformation of methyl (R)-ricinoleate into methyl (S)-ricinoleate (95.6% ee)Figure optionsDownload full-size imageDownload as PowerPoint slide