Additive-assisted preferential crystallization of racemic component: A case of norvaline

•A preferential crystallization process of norvaline performed near the eutectic composition was established.•Additive-assisted preferential crystallization boosts purity up to 98% with 56% yield.•Tailor-made additives selectively suppress crystallization of racemate not enantiomer.•Molecular mechanism of selective inhibition by tailor-made additives was elucidated.