Synthesis and biological evaluation of enantiomerically pure pyrrolyl-oxazolidinones as a new class of potent and selective monoamine oxidase type A inhibitors

Abstract

Due to the key role played by monoamine oxidases (MAOs) in the metabolism of neurotransmitters, MAO inhibitors (MAOIs) represent an useful tool for the treatment of several neurological diseases. Among selective MAOIs, MAO-A inhibitors (e.g. clorgyline) are used as antidepressant and antianxiety drugs and are claimed to protect neuronal cells against apoptosis, and selective MAO-B inhibitors (e.g. L-deprenyl) can be used in the treatment of Parkinson's disease either alone or in combination with L-DOPA. However, they engender covalent bonds with the active site of the enzyme and induce irreversible inhibition; moreover, they tend to lose their initial selectivity at high dosages or with repeated administrations. Phenyloxazolidinones belong to third-generation-MAOIs, characterized by a selective and reversible inhibition of the enzyme. Among these molecules, the most representative are toloxatone and befloxatone, two selective and reversible MAO-A inhibitors used in therapy as antidepressant drugs. Going on our searches on CNS potentially active compounds containing a pyrrole moiety we prepared 3-(1H-pyrrol-1-yl)-2-oxazolidinones (1) and isomeric 3-(1H-pyrrol-2-and -3-yl)-2-oxazolidinones (2 and 3) as anti-MAO agents. Such derivatives resulted selective and reversible MAO-A inhibitors. The most potent compound is (R)-5-methoxymethyl-3-(1H-pyrrol-1-yl)-2-oxazolidinone (1b), endowed with very high potency (K(iMAO-A) = 4.9 nM) and A-selectivity (A-selectivity = 10,200, about 116-fold greater than that of befloxatone).