Biocatalytic, Decarboxylative Addition of Malonates to Imines, a ”Rodionovase"

Significance

Enolate anions are common carbon nucleophiles in organic synthesis. Herein, the authors demonstrate a biocatalytic addition of enolates to imines to afford N-heterocycles with high diastereoselectivity by using carboxymethylproline synthases (CMPSs), which are known to use enolate intermediates. Proper substitution of residues in the reaction site, especially the oxy-anion hole, gave mutants of higher reactivity and stereoselectivity than the wild-type enzymes. Moreover, engineered CMPSs could generate both diastereomers with good stereoselectivity. Also, control experiments with enantioenriched 2 imply stereospecific enolate stabilization in the reaction site prior to the ­diastereoselective addition to imines.