Organocatalytic conversion of arylglyoxals into optically active mandelic acid derivatives

A novel protocol for the organocatalytic conversion of arylglyoxals into the corresponding α-hydroxy arylacetic acid methyl esters has been developed. The catalyst consists of a combination of a commercially available cinchona alkaloid derivative and an achiral thiol and leads to enantiomerically enriched products (eemax 83%) under mild reaction conditions. The alkaloid can be easily recovered and reused without loss in activity and selectivity.