1,3,4-Oxadiazol-2-ones as fatty-acid amide hydrolase and monoacylglycerol lipase inhibitors: Synthesis, in vitro evaluation and insight into potency and selectivity determinants by molecular modelling.

Inhibition of the key hydrolytic enzymes of the endocannabinoid system, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), has been proposed as potential mode of action for various therapeutic applications. Continuing our previous work, we take the first steps of structure-activity relationship exploration and show that 1,3,4-oxadiazol-2-ones can serve as scaffold for both selective FAAH and MAGL inhibitors, and also function as a dual FAAH/MAGL inhibitor at sub-micromolar IC50 values. Moreover, 10-fold selectivity against MAGL over FAAH was achieved with compound 3d (FAAH and MAGL IC50; 2.0 and 0.22 µM). Lastly, enzyme and ligand features contributing to the potency and selectivity differences are analysed by molecular docking.

Discovery and development of endocannabinoid-hydrolyzing enzyme inhibitors.

Fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGL) are hydrolytic enzymes which degrade the endogenous cannabinoids (endocannabinoids) N-arachidonoylethanolamine (anandamide, AEA) and 2-arachidonoylglycerol (2-AG), respectively. Endocannabinoids are an important class of lipid messenger molecules that are produced on demand in response to elevated intracellular calcium levels. They recognize and activate the cannabinoid CB(1) and CB(2) receptors, the molecular targets for Delta(9)-tetrahydrocannabinol (Delta(9)-THC) in marijuana evoking several beneficial therapeutic effects. However, in vivo the cannabimimetic effects of AEA and 2-AG remain weak owing to their rapid inactivation by FAAH and MGL, respectively. The inactivation of FAAH and MGL by specific enzyme inhibitors increases the levels of AEA and 2-AG, respectively, producing therapeutic effects such as pain relief and depression of anxiety.

Characterization of binding properties of monoglyceride lipase inhibitors by a versatile fluorescence-based technique.

Monoglyceride lipase (MGL) is a serine hydrolase that terminates the signaling of the primary endocannabinoid, 2-arachidonoyl glycerol (2-AG). Versatile high-throughput screening methods allowing the testing of MGL inhibitors are rare, thereby limiting the development and analysis of novel inhibitors. Here we describe an improved fluorescence-based technique that is capable of determining time- and dose-dependent inhibition of MGL with one or multiple binding sites and, at the same time, is capable of revealing the reversibility of inhibitor binding in a simple kinetic assay format. Known reference compounds as well as novel inhibitors, such as JZL184 and CAY10499, were evaluated for their MGL-binding properties and potency.

3-Heterocycle-phenyl N-alkylcarbamates as FAAH inhibitors: design, synthesis and 3D-QSAR studies.

Carbamates are a well-established class of fatty acid amide hydrolase (FAAH) inhibitors. Here we describe the synthesis of meta-substituted phenolic N-alkyl/aryl carbamates and their in vitro FAAH inhibitory activities. The most potent compound, 3-(oxazol-2yl)phenyl cyclohexylcarbamate (2 a), inhibited FAAH with a sub-nanomolar IC(50) value (IC(50)=0.74 nM). Additionally, we developed and validated three-dimensional quantitative structure-activity relationships (QSAR) models of FAAH inhibition combining the newly disclosed carbamates with our previously published inhibitors to give a total set of 99 compounds. Prior to 3D-QSAR modeling, the degree of correlation between FAAH inhibition and in silico reactivity was also established. Both 3D-QSAR methods used, CoMSIA and GRID/GOLPE, produced statistically significant models with coefficient of correlation for external prediction (R(2) (PRED)) values of 0.732 and 0.760, respectively. These models could be of high value in further FAAH inhibitor design.

The synthesis and biological evaluation of para-substituted phenolic N-alkyl carbamates as endocannabinoid hydrolyzing enzyme inhibitors.

A series of para-substituted phenolic N-alkyl carbamates were evaluated for their FAAH and MGL inhibitory activities. The compounds were generally selective for FAAH, with IC(50) values in the nM range, whereas inhibition of MGL required concentrations three orders of magnitude higher. The most potent compounds, dodecylcarbamic acid 4-(4,5-dihydrothiazol-2-yl)phenyl (12) and 4-(1,2,3-thiadiazol-4-yl)phenyl (26) esters, inhibited FAAH and MGL with IC(50) values at the low-nanomolar (IC(50)s; 0.0063 and 0.012 microM) and the low-micromolar ranges (IC(50)s; 2.1 and 1.0 microM), respectively. Compound 26 also inhibited both FAAH-dependent AEA uptake and AEA hydrolysis (IC(50); 0.082 microM) by intact RBL2H3 cells, and could also reduce 2-AG hydrolysis by these cells at concentrations >or=0.030 microM.

Discovery of boronic acids as novel and potent inhibitors of fatty acid amide hydrolase.

A series of commercial phenyl-, heteroaryl-, alkyl-, and alkenylboronic acids were evaluated for their FAAH and MGL inhibitory activities. The compounds were generally selective for FAAH, with IC50 in the nanomolar or low-micromolar range. Eight of these compounds inhibited MGL with IC50 in the micromolar range. The most potent compound, phenylboronic acid with para-nonyl substituent (13), inhibited FAAH and MGL with IC50 of 0.0091 and 7.9 microM, respectively.

Bisoxazoline-Lewis acid-catalyzed direct-electron demand oxo-hetero-Diels-Alder reactions of N-oxy-pyridine aldehyde and ketone derivatives.

A general catalytic oxo-hetero-Diels-Alder reaction for pro-chiral aldehyde and ketone N-oxy-pyridines is presented. The catalytic and asymmetric oxo-hetero-Diels-Alder reaction of electron-rich dienes with N-oxy-pyridine-2-carbaldehyde and ketone derivatives, catalyzed by chiral copper(II)-bisoxazoline complexes, gives optically active six-membered oxygen heterocycles in moderate to good yields and with excellent enantioselectivities.

Bis(oxazoline) Lewis acid catalyzed aldol reactions of pyridine N-oxide aldehydes--synthesis of optically active 2-(1-hydroxyalkyl)pyridine derivatives: development, scope, and total synthesis of an indolizine alkaloid.

A new, short, and simplified procedure for the synthesis of optically active pyridine derivatives from pro-chiral pyridine-N-oxides is presented. The catalytic and asymmetric Mukaiyama aldol reaction between ketene silyl acetals and 1-oxypyridine-2-carbaldehyde derivatives catalyzed by chiral copper(II)-bis(oxazoline) complexes gave optically active 2-(hydroxyalkyl)- and 2-(anti-1,2-dihydroxyalkyl)pyridine derivatives in good yields and diastereoselectivities, and in excellent enantioselectivities-up to 99 % enantiomeric excess. As a synthetic application of the developed method, a full account for the asymmetric total synthesis of a nonnatural indolizine alkaloid is provided.