Trichosporon cutaneum-promoted deracemization of (±)-2-hydroxindan-1-one: a mechanistic study

A mechanistic study of the deracemization of (±)-2-hydroxy-1-indanone mediated by the yeast Trichosporon cutaneum to afford pure (1S,2R)-1,2-indandiol is reported. The key aspect of the study was the use of pure (R)- and (S)-2-hydroxy-1-indanone enantiomers to ensure reliable conclusions. Experiments in the absence of yeast cells or using dead cells disclosed that the pure enantiomers were not racemized, which suggest that the whole dynamic kinetic resolution process is enzymatic in character. When living yeast cells were used the (R)-substrate was smoothly converted to (1S,2R)-1,2-indandiol, whilst the (S)-2-hydroxy-1-indanone was converted to the same diol through a more complex fashion, which requires a more lengthy oxidation-reduction pathway having the 1,2-indanedione as an achiral intermediate. An unexpected observation was that 1,2-indanone acts as a moderate inhibitor of the reductive enzymes acting in the conversion of (R)-2-hydroxy-1-indanone to (1S,2R)-1,2-indandiol.