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

The first total synthesis of isoindolinone (+/-)-en-tonalactam A (6), originally obtained from the fungus Entonaema sp., was achieved in 14 steps from commercially available 5bromovanillin 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 mu M, respectively).