(2S)-2-hydroxy-2-phenylacetonitrile

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Yamamoto et al. (1991) tested various isolates (wildtype strains) with respect to their ability to convert mandelonitrile into (R)-(−)-mandelic acid. A. faecalis strain ATCC 8750 was found to have the highest level of activity and enantioselectivity to produce (R)-(−)-mandelic acid from racemic mandelonitrile (Yamamoto et al., 1991). In particular, the (R)-(−)-mandelic acid made of mandelonitrile by resting cells was present in a 100% enantiomeric excess. A. faecalis ATCC 8750 has an (R)-enantioselective nitrilase and an amidase used to process mandelonitrile and mandelamide, respectively. As (R)-(−)-mandelic acid was produced from racemic mandelonitrile in a yield of 91%, whereas no (S)-mandelonitrile was left, the (S)-(−)-mandelonitrile remaining in the reaction is spontaneously racemised because of the chemical equilibrium of the (R)- and the (S)-isomer of mandelonitrile on the one hand and benzaldehyde/HCN on the other hand. Consequently, almost all the mandelonitrile is consumed and converted to (R)-(−)-mandelic acid. It is noted that, according to Yamamoto et al. (1991), the A. faecalis cells employed for production of (R)-mandelic acid require specifically optimized culture conditions.