Total Synthesis and Monoamine Oxidase Inhibitory Activities of (±)-Entonalactam A and Its Derivatives.

The first total synthesis of isoindolinone (±)-entonalactam A (6), originally obtained from the fungus Entonaema sp., was achieved in 14 steps from commercially available 5-bromovanillin via benzophenone intermediates. Isoindolinone, phthalide, and benzophenone analogues of natural products were also synthesized. The monoamine oxidase (MAO) A and B inhibitory activities were tested. The isoindolinone derivative 30 exhibited inhibition of both MAO-A and -B (IC50 = 17.8 and 15.8 µM, respectively).