Diisopropyl Malonate as Acylating Agent in Kinetic Resolution of Chiral Amines with Lipase B from Candida antarctica
Activity of diisopropyl malonate (2) as a novel acylating agent was investigated in kinetic resolution (KR) of various racemic amines [(±)-1a-d] catalyzed by lipase B from Candida antarctica. Diisopropyl malonate (2) proved to be effective acylating agent with four racemic amines [(±)-2-aminoheptane, (±)-1-methoxy-2-propylamine, (±)-1-phenylethylamine and (±)-4-phenylbutan-2-amine; (±)-1a-d, respectively] selected for this study. The lipase-catalyzed acylation of the amines (±)-1a-d with 2 proceeded with good conversions (44.9–52.1%) and provided the expected (R)-amides [(R)-3a-d] in moderate to excellent yields (51–98%) with high enantiomeric excess (ee(R)-3a-d 92.0–99.9%) after 4 h reaction time under mild reaction conditions in batch mode. The best conversion (50%) combined with high enantiomeric purity (ee(R)-2d > 99%ee) was achieved in the KR from racemic 2-aminoheptane (±)-1a. The four novel (R)-amides [(R)-3a-d] were isolated and properly characterized.