Synthesis and Structure–Activity Relationship (SAR) of 2-Methyl-4-oxo-3-oxetanylcarbamic Acid Esters, a Class of Potent N-Acylethanolamine Acid Amidase (NAAA) Inhibitors

N-Acylethanolamine acid amidase (NAAA) is a lysosomal cysteine hydrolase involved in the degradation of saturated and monounsaturated fatty acid ethanolamides (FAEs), a family of endogenous lipid agonists of peroxisome proliferator-activated receptor-α, which include oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). The β-lactone derivatives (S)-N-(2-oxo-3-oxetanyl)-3-phenylpropionamide (2) and (S)-N-(2-oxo-3-oxetanyl)-biphenyl-4-carboxamide (3) inhibit NAAA, prevent FAE hydrolysis in activated inflammatory cells, and reduce tissue reactions to pro-inflammatory stimuli. Recently, our group disclosed ARN077 (4), a potent NAAA inhibitor that is active in vivo by topical administration in rodent models of hyperalgesia and allodynia. In the present study, we investigated the structure–activity relationship (SAR) of threonine-derived β-lactone analogues of compound 4. The main results of this work were an enhancement of the inhibitory potency of β-lactone carbamate derivatives for NAAA and the identifi...