Synthesis and QSAR of Fatty Acid Amide Hydrolase Inhibitors: Modulation at the N-Portion of Biphenyl-3-yl Alkylcarbamates

Alkylcarbamic acid biphenyl-3-yl esters are a class of fatty acid amide hydrolase (FAAH) inhibitors that comprises cyclohexylcarbamic acid 3′-carbamoylbiphenyl-3-yl ester (URB597), a compound with analgesic, anxiolytic-like and antidepressant-like properties in rat and mouse models. Here, we extended the structure-activity relationships (SARs) for this class of compounds by replacing the cyclohexyl ring of the parent compound cyclohexylcarbamic acid biphenyl-3-yl ester (URB524) (IC 50 , for FAAH = 63 nM) with a selected set of substituents of different size, shape, flexibility and lipophilicity. Docking experiments and Linear Interaction Energy (LIE) calculations indicated that the N-terminal group of O -arylcarbamates fits within the lipophilic region of the substrate-binding site, mimicking the arachidonoyl chain of anandamide. Significant potency improvements were observed for the β-naphthylmethyl derivative 4q (IC 50 = 5.3 nM) and its 3′-carbamoylbiphenyl-3-yl ester 4z (URB880, IC 50 = 0.63 nM), indicating that shape complementarity and hydrogen bonds are crucial to obtain highly potent inhibitors.