A study of the structure-activity relationships (SAR) of 2f (OL-135), a potent inhibitor of fatty acid amide hydrolase (FAAH), is detailed targeting the 5-position of the oxazole. Examination of a series of substituted benzene derivatives (12)(13)(14) revealed that the optimal position for substitution was the meta-position with selected members approaching or exceeding the potency of 2f. Concurrent with these studies, the effect of substitution on the pyridine ring of 2f was also examined. A series of small, non-aromatic C5-substituents was also explored and revealed that the K i follows a well-defined correlation with the Hammett σ p constant (ρ = 3.01, R 2 = 0.91) in which electron-withdrawing substituents enhance potency leading to inhibitors with K i 's as low as 400 pM (20n). Proteomic-wide screening of the inhibitors revealed that most are exquisitely selective for FAAH over all other mammalian proteases reversing the 100-fold preference of 20a (C5 substituent = H) for the enzyme TGH.Fatty acid amides are an important new class of lipid signaling molecules that modulate a number of physiological processes. Two endogenous fatty acid amides, anandamide (1a) 1 and oleamide (1b), 2-4 have emerged as prototypical members of this class that serve as chemical messengers (Figure 1). Anandamide (1a), which was only discovered a little more than a decade ago and is the most recognizable member of the endogenous fatty acid ethanolamides, 5 binds and activates both the central type-1 (CB1) and peripheral type-2 (CB2) cannabinoid receptors. Anandamide (1a), and members of the cannabinoid family, 6 have been implicated in the modulation of nociception, 7-9 feeding, 10,11 emesis, anxiety, 12 cell proliferation, 13,14 inflammation, 15 memory 16 and neuroprotection after brain injury. 17 Thus, the cannabinoids have clinical relevance for analgesia, anxiety, epilepsy, cachexia, cancer, and Alzheimer's disease as well as other neurodegenerative diseases. 18-20 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptOleamide (1b) was found to accumulate in the cerebrospinal fluid of animals under conditions of sleep deprivation and to induce physiological sleep in a dose dependent manner where it reduced motility, shortened the sleep induction period, and lengthened the time spent in slow wave sleep 2 at the expense of wakening. 2,4 In a structurally specific manner, it was found to modulate serotonergic systems 21-23 and GABAergic transmission, 24,25 block glial gap junction cell-cell communication, 26,27 decrease body temperature and locomotor activity, 28 and exhibit the characteristic in vivo analgesic and cannabinoid behavorial effects of anandamide, 21,29 albeit without direct cannabinoid receptor activation. It has been suggested that the cannabinoid behavorial effects of oleamide (1b) may be mediated through an as yet unknown distinct pharmacological target. 24 Because oleamide (1b) may play a critical role in sleep, it may provide an exciting therapeutic potential for the development of sle...

The first total synthesis of chloropeptin II (1, complestatin) is disclosed. Key elements of the approach include the use of an intramolecular Larock indole synthesis for the initial macrocyclization, adopting conditions that permit utilization of a 2-bromoaniline, incorporating a terminal alkyne substituent (−SiEt3) that sterically dictates the indole cyclization regioselectivity, and benefiting from an aniline protecting group (−Ac) that enhances the atropdiastereoselectivity and diminishes the strained indole reactivity toward subsequent electrophilic reagents. Not only did this key reaction provide the fully functionalized right-hand ring system of 1 in superb conversion (89%) and good atropdiastereoselectivity (4:1 R: S), but it also represents the first reported example of what will prove to be a useful Larock macrocyclization strategy. Subsequent introduction of the left-hand ring system enlisting an aromatic nucleophilic substitution reaction for macrocyclization with biaryl ether formation completed the assemblage of the core bicyclic structure of 1. Intrinsic in the design of the approach and by virtue of the single-step acid-catalyzed conversion of chloropeptin II (1) to chloropeptin I (2), the route also provides a total synthesis of 2.

A series of alpha-ketooxazoles containing conformational constraints in the flexible C2 acyl side chain of 2 (OL-135) and representative oxazole C5 substituents were prepared and examined as inhibitors of fatty acid amide hydrolase (FAAH). Exceptionally potent and selective FAAH inhibitors emerged from the series (e.g., 6, Ki = 200 and 260 pM for rat and rhFAAH). With simple and small C5 oxazole substituents, each series bearing a biphenylethyl, phenoxyphenethyl, or (phenoxymethyl)phenethyl C2 side chain was found to follow a well-defined linear relationship between -log Ki and Hammett sigmap of a magnitude (rho = 2.7-3.0) that indicates that the substituent electronic effect dominates, confirming its fundamental importance to the series and further establishing its predictive value. Just as significantly, the nature of the C5 oxazole substituent substantially impacts the selectivity of the inhibitors whereas the effect of the C2 acyl chain was more subtle but still significant even in the small series examined. Combination of these independent features, which display generalized trends across a range of inhibitor series, simultaneously improves FAAH potency and selectivity and can provide exquisitely selective and potent FAAH inhibitors.

Three cocrystal X-ray structures of the α-ketoheterocycle inhibitors 3–5 bound to a humanized variant of fatty acid amide hydrolase (FAAH) are disclosed and comparatively discussed alongside those of 1 (OL-135) and its isomer 2. These five X-ray structures systematically probe each of the three active site regions key to substrate or inhibitor binding: (1) the conformationally mobile acyl chain-binding pocket and membrane access channel responsible for fatty acid amide substrate and inhibitor acyl chain binding, (2) the atypical active site catalytic residues and surrounding oxyanion hole that covalently binds the core of the α-ketoheterocycle inhibitors captured as deprotonated hemiketals mimicking the tetrahedral intermediate of the enzyme catalyzed reaction, and (3) the cytosolic port and its uniquely important imbedded ordered water molecules and a newly identified anion binding site. The detailed analysis of their key active site interactions and their implications on the interpretation of the available structure–activity relationships are discussed providing important insights for future design.