More active enantiomer of the PDE4 inhibitor rolipram (4-(3-(Cyclopentyloxy)-4-methoxyphenyl)pyrrolidin-2-one ); 2-10-fold more potent than the S-(+) enantiomer ((4S)-4-[3-(Cyclopentyloxy)-4-methoxyphenyl]pyrrolidin-2-one ). Also available as part of the Phosphodiesterase Inhibitor Tocriset™ .