(S)-1-(Pent-4'-enoyl)-4-(hydroxymethyl)-azetidin-2-one derivatives as inhibitors of human fatty acid amide hydrolase (hFAAH): synthesis, biological evaluation and molecular modelling.

A series of lipophilic ester derivatives (2a-g) of (S)-1-(pent-4'-enoyl)-4-(hydroxymethyl)-azetidin-2-one has been synthesised in three steps from (S)-4-(benzyloxycarbonyl)-azetidin-2-one and evaluated as novel, reversible, ß-lactamic inhibitors of endocannabinoid-degrading enzymes (human fatty acid amide hydrolase (hFAAH) and monoacylglycerol lipase (hMAGL)). The compounds showed IC50 values in the micromolar range and selectivity for hFAAH versus hMAGL. The unexpected 1000-fold decrease in activity of 2a comparatively to the known regioisomeric structure 1a (i.e. lipophilic chains placed on N1 and C3 positions of the ß-lactam core) could be explained on the basis of docking studies into a revisited model of hFAAH active site, considering one or two water molecules in interaction with the catalytic triad.

Vibrational circular dichroism versus optical rotation dispersion and electronic circular dichroism for diastereomers: the stereochemistry of 3-(1'-hydroxyethyl)-1-(3'-phenylpropanoyl)-azetidin-2-one.

The absolute configuration of a relatively large and conformationally flexible chiral compound, 3-(1'-hydroxyethyl)-1-(3'-phenylpropanoyl)-azetidin-2-one, is determined using Vibrational Circular Dichroism (VCD) spectroscopy, Optical Rotation Dispersion (ORD) and Electronic Circular Dichroism (ECD). To that end a state of the art experimental VCD spectrum is compared to a theoretical spectrum and the absolute configuration is assigned. ORD and ECD are also used in the assignment to investigate the complementarity of the three techniques. VCD spectroscopy is found to have important advantages over ORD and ECD for diastereomers. The concept of robust modes is applied to this conformationally flexible molecule, showing that its use is limited for such large and flexible molecules.

An unprecedented reversible mode of action of ß-lactams for the inhibition of human fatty acid amide hydrolase (hFAAH).

A series of compound was prepared to clarify the reversible mechanism of ß-lactamic hFAAH inhibitors on the one hand, and to modulate some of their physicochemical parameters on the other hand. In particular, two compounds (4b and 4e) were designed to display a potential good leaving group on the crucial carbonyl with a view to possibly acylating the active serine of the hFAAH catalytic triad. Reversibility studies showed that these two compounds retain the reversible mode of inhibition, suggesting a noncovalent interaction between our ß-lactams and hFAAH. Finally, pharmacological evaluations of bioisosteres of the lead compound (4a, IC(50) = 5.3 nM) revealed that log P values and PSA could be optimized without altering the FAAH inhibition (IC(50) values from 3.65 nM to 70.9 nM).

Inhibitors of the endocannabinoid-degrading enzymes, or how to increase endocannabinoid's activity by preventing their hydrolysis.

Endocannabinoids are lipid transmitters binding and activating the cannabinoid receptors. Both cannabinoid receptors and endocannabinoids, such as 2-arachidonoylglycerol and anandamide, have been shown to control numerous physiological and pathological processes, including in the central nervous system. Thus regulating endocannabinoid levels in-vivo represents an interesting therapeutic perspective in several CNS-related diseases. To date four enzymes - Fatty Acid Amide Hydrolase (FAAH), N-Acylethanolamine-hydrolyzing Acid Amidase (NAAA), Monoacylglycerol Lipase (MAGL), α/ß-Hydrolase Domain 6 (ABHD6) - were shown to control endocannabinoid levels in tissues or in intact cells. While the searches for NAAA and ABHD6 inhibitors are still in their beginning, a growing number of selective and potent inhibitors are now available to inhibit FAAH and MAGL activities. Here, based on the literature and patent literature, we review the compounds of the different chemical families that have been developed to inhibit these enzymes, with a special emphasis on FAAH and MAGL inhibitors.

SAR and LC/MS studies of ß-lactamic inhibitors of human fatty acid amide hydrolase (hFAAH): evidence of a nonhydrolytic process.

The endocannabinoid hydrolyzing enzyme FAAH uses a nonclassical catalytic triad (namely, Ser-Ser-Lys instead of Ser-Asp-His) to cleave its endogenous substrates. Because inhibiting FAAH has a clear therapeutic potential, we previously developed ß-lactam-type inhibitors of hFAAH. Here, we report the synthesis of five novel derivatives (5-9) of our lead compound 1-(pent-4-enoyl)-3(S)-[1(R)-(4-phenylbutanoyloxy)-ethyl]-azetidin-2-one (4, IC(50) = 5 nM) obtained via the systematic replacement of one to three carbonyls by methylene groups. The SAR results showed that the imide, but not the lactam, function is essential to the inhibition of hFAAH. We also performed LC/MS analysis following incubation of our inhibitors with hFAAH or mouse liver. We demonstrated that hFAAH interacts with these ß-lactam-type inhibitors but, unexpectedly, does not open the ß-lactam moiety. This mechanism seems to be unique to FAAH because the ß-lactam function of the inhibitors is hydrolyzed when they are incubated in the presence of the serine hydrolases expressed in the mouse liver. Finally, we confirmed these results by showing that a highly selective FAAH inhibitor (PF-750) does not prevent this hydrolysis by liver homogenates.

beta-Lactams derived from a carbapenem chiron are selective inhibitors of human fatty acid amide hydrolase versus human monoacylglycerol lipase.

A library of 30 beta-lactams has been prepared from (3R,4R)-3-[(R)-1'-(tbutyldimethylsilyloxy)-ethyl]-4-acetoxy-2-azetidinone, and the corresponding deacetoxy derivative, by sequential N- and O-functionalizations with various omega-alkenoyl and omega-arylalkanoyl chains. All compounds were selective inhibitors of hFAAH versus hMGL, and IC(50) values in the nanomolar range (5-14 nM) were recorded for the best representatives. From time-dependent preincubation and rapid dilution studies, and from docking analyses in a homology model of the target enzyme, a reversible mechanism of inhibition of hFAAH is proposed.