Highly specific σ2R/TMEM97 ligand FEM-1689 alleviates neuropathic pain and inhibits the integrated stress response.

The sigma 2 receptor (σ2R) was described pharmacologically more than three decades ago, but its molecular identity remained obscure until recently when it was identified as transmembrane protein 97 (TMEM97). We and others have shown that σ2R/TMEM97 ligands alleviate mechanical hypersensitivity in mouse neuropathic pain models with a time course wherein maximal antinociceptive effect is approximately 24 h following dosing. We sought to understand this unique antineuropathic pain effect by addressing two key questions: do these σ2R/TMEM97 compounds act selectively via the receptor, and what is their downstream mechanism on nociceptive neurons? Using male and female conventional knockout mice for Tmem97, we find that a σ2R/TMEM97 binding compound, FEM-1689, requires the presence of the gene to produce antinociception in the spared nerve injury model in mice. Using primary mouse dorsal root ganglion neurons, we demonstrate that FEM-1689 inhibits the integrated stress response (ISR) and promotes neurite outgrowth via a σ2R/TMEM97-specific action. We extend the clinical translational value of these findings by showing that FEM-1689 reduces ISR and p-eIF2α levels in human sensory neurons and that it alleviates the pathogenic engagement of ISR by methylglyoxal. We also demonstrate that σ2R/TMEM97 is expressed in human nociceptors and satellite glial cells. These results validate σ2R/TMEM97 as a promising target for further development for the treatment of neuropathic pain.

Highly specific σ2R/TMEM97 ligand alleviates neuropathic pain and inhibits the integrated stress response.

The Sigma 2 receptor (σ2R) was described pharmacologically more than three decades ago, but its molecular identity remained obscure until recently when it was identified as transmembrane protein 97 (TMEM97). We and others have shown that σ2R/TMEM97 ligands alleviate mechanical hypersensitivity in mouse neuropathic pain models with a time course wherein maximal anti-nociceptive effect is approximately 24 hours following dosing. We sought to understand this unique anti-neuropathic pain effect by addressing two key questions: do these σ2R/TMEM97 compounds act selectively via the receptor, and what is their downstream mechanism on nociceptive neurons? Using male and female conventional knockout (KO) mice for Tmem97, we find that a new σ2R/TMEM97 binding compound, FEM-1689, requires the presence of the gene to produce anti-nociception in the spared nerve injury model in mice. Using primary mouse dorsal root ganglion (DRG) neurons, we demonstrate that FEM-1689 inhibits the integrated stress response (ISR) and promotes neurite outgrowth via a σ2R/TMEM97-specific action. We extend the clinical translational value of these findings by showing that FEM-1689 reduces ISR and p-eIF2α levels in human sensory neurons and that it alleviates the pathogenic engagement of ISR by methylglyoxal. We also demonstrate that σ2R/TMEM97 is expressed in human nociceptors and satellite glial cells. These results validate σ2R/TMEM97 as a promising target for further development for the treatment of neuropathic pain.

MNK1 and MNK2 Expression in the Human Dorsal Root and Trigeminal Ganglion.

Mitogen activated protein kinase interacting kinases (MNK) 1 and 2 are serine/threonine protein kinases that play an important role in translation of mRNAs through their phosphorylation of the RNA 5'-cap binding protein, eukaryotic translation initiation factor (eIF) 4E. These kinases are downstream targets for mitogen activated protein kinases (MAPKs), extracellular activity regulated protein kinase (ERK) and p38. MNKs have been implicated in the sensitization of peripheral nociceptors of the dorsal root and trigeminal ganglion (DRG and TG) using transgenic mouse lines and through the use of specific inhibitors of MNK1 and MNK2. While specific knockout of the Mknk1 gene suggests that it is the key isoform for regulation of nociceptor excitability and nociceptive behaviors in mice, both MKNK1 and MKNK2 genes are expressed in the DRG and TG of mice and humans based on RNA sequencing experiments. Single cell sequencing in mice suggests that Mknk1 and Mknk2 may be expressed in different populations of nociceptors. We sought to characterize mRNA expression in human DRG and TG (N = 3 ganglia for both DRG and TG) for both MNK1 and MNK2. Our results show that both genes are expressed by nearly all neurons in both human ganglia with expression in other cell types as well. Our findings provide evidence that MNK1 and MNK2 are expressed by human nociceptors of males and females and suggest that efforts to pharmacologically target MNKs for pain would likely be translatable due its conserved expression in both species.

MNK1 and MNK2 expression in the human dorsal root and trigeminal ganglion.

Mitogen activated protein kinase interacting kinases (MNK) 1 and 2 are serine/threonine protein kinases that play an important role in translation of mRNAs through their phosphorylation of the RNA 5’-cap binding protein, eukaryotic translation initiation factor (eIF) 4E. These kinases are downstream targets for mitogen activated protein kinases (MAPKs), extracellular activity regulated protein kinase (ERK) and p38. MNKs have been implicated in the sensitization of peripheral nociceptors of the dorsal root and trigeminal ganglion (DRG and TG) using transgenic mouse lines and through the use of specific inhibitors of MNK1 and MNK2. While specific knockout of the Mknk1 gene suggests that it is the key isoform for regulation of nociceptor excitability and nociceptive behaviors in mice, both MKNK1 and MKNK2 genes are expressed in the DRG and TG of mice and humans based on RNA sequencing experiments. Single cell sequencing in mice suggests that Mknk1 and Mknk2 may be expressed in different populations of nociceptors. We sought to characterize mRNA expression in human DRG and TG for both MNK1 and MNK2. Our results show that both genes are expressed by nearly all neurons in both human ganglia with expression in other cell types as well. Our findings provide evidence that MNK1 and MNK2 are expressed by human nociceptors and suggest that efforts to pharmacologically target MNKs for pain would likely be translatable due its conserved expression in both species.

σ2R/TMEM97 in retinal ganglion cell degeneration.

The sigma 2 receptor (σ2R) was recently identified as an endoplasmic reticulum (ER) membrane protein known as transmembrane protein 97 (TMEM97). Studies have shown that σ2R/TMEM97 binding compounds are neuroprotective, suggesting a role of σ2R/TMEM97 in neurodegenerative processes. To understand the function of σ2R/TMEM97 in neurodegeneration pathways, we characterized ischemia-induced retinal ganglion cell (RGC) degeneration in TMEM97-/- mice and found that RGCs in TMEM97-/- mice are resistant to degeneration. In addition, intravitreal injection of a selective σ2R/TMEM97 ligand DKR-1677 significantly protects RGCs from ischemia-induced degeneration in wildtype mice. Our results provide conclusive evidence that σ2R/TMEM97 plays a role to facilitate RGC death following ischemic injury and that inhibiting the function of σ2R/TMEM97 is neuroprotective. This work is a breakthrough toward elucidating the biology and function of σ2R/TMEM97 in RGCs and likely in other σ2R/TMEM97 expressing neurons. Moreover, these findings support future studies to develop new neuroprotective approaches for RGC degenerative diseases by inhibiting σ2R/TMEM97.

Neuroprotective Effects of σ2R/TMEM97 Receptor Modulators in the Neuronal Model of Huntington's Disease.

Huntington's disease (HD) is a genetic neurodegenerative disease caused by an expanded CAG repeat in the Huntingtin (HTT) gene that encodes for an expanded polyglutamine (polyQ) repeat in exon-1 of the human mutant huntingtin (mHTT) protein. The presence of this polyQ repeat results in neuronal degeneration, for which there is no cure or treatment that modifies disease progression. In previous studies, we have shown that small molecules that bind selectively to σ2R/TMEM97 can have significant neuroprotective effects in models of Alzheimer's disease, traumatic brain injury, and several other neurodegenerative diseases. In the present work, we extend these investigations and show that certain σ2R/TMEM97-selective ligands decrease mHTT-induced neuronal toxicity. We first synthesized a set of compounds designed to bind to σ2R/TMEM97 and determined their binding profiles (Ki values) for σ2R/TMEM97 and other proteins in the central nervous system. Modulators with high affinity and selectivity for σ2R/TMEM97 were then tested in our HD cell model. Primary cortical neurons were cultured in vitro for 7 days and then co-transfected with either a normal HTT construct (Htt N-586-22Q/GFP) or the mHTT construct Htt-N586-82Q/GFP. Transfected neurons were treated with either σ2R/TMEM97 or σ1R modulators for 48 h. After treatment, neurons were fixed and stained with Hoechst, and condensed nuclei were quantified to assess cell death in the transfected neurons. Significantly, σ2R/TMEM97 modulators reduce the neuronal toxicity induced by mHTT, and their neuroprotective effects are not blocked by NE-100, a selective σ1R antagonist known to block neuroprotection by σ1R ligands. These results indicate for the first time that σ2R/TMEM97 modulators can protect neurons from mHTT-induced neuronal toxicity, suggesting that targeting σ2R/TMEM97 may lead to a novel therapeutic approach to treat patients with HD.

Targeting σ2R/TMEM97 with novel aminotetralins.

Initially associated with cancer diagnosis and therapy, the sigma 2 receptor (σ2R) has recently been implicated in several disorders of the central nervous system (CNS). It remained a poorly characterized target until we identified it as the transmembrane protein 97 (TMEM97). As part of a program to identify novel compounds that bind with high affinity and selectivity to σ2R/TMEM97 relative to the sigma 1 receptor (σ1R) and other CNS proteins, we employed a scaffold simplification strategy to design novel sets of piperazine-substituted aminotetralins based on analogous norbenzomorphans that we previously developed. JVW-1601 was identified as a reference aminotetralin analog that had high affinity (Ki = 5.5 nM) and selectivity (36-fold) for σ2R/TMEM97 versus σ1R. An expanded investigation of structure-activity relationships (SAR) in several structural regions of this compound was conducted, and among the ligands thus prepared, many had Ki values < 20 nM for σ2R/TMEM97 and selectivities of >20-fold versus σ1R. Structural features that enhance σ2R/TMEM97 affinity and selectivity were identified, leading to an optimized compound having a high σ2R/TMEM97 affinity (Ki of 4.5 nM) and 366-fold selectivity relative to σ1R. Significantly, during the course of this work we discovered JVW-1625, which enabled the isolation and identification of σ2R as TMEM97 and resolved a question that had eluded researchers for decades. Computational docking studies for selected aminotetralins suggest they adopt similar poses upon binding to σ2R/TMEM97, engaging in highly conserved salt bridges with Asp29 and cation-π interactions with Tyr150. Collectively, these studies show that aminotetralins are useful tool compounds for studying the mechanism and function of σ2R/TMEM97.

Pharmacological Manipulation of Translation as a Therapeutic Target for Chronic Pain.

Dysfunction in regulation of mRNA translation is an increasingly recognized characteristic of many diseases and disorders, including cancer, diabetes, autoimmunity, neurodegeneration, and chronic pain. Approximately 50 million adults in the United States experience chronic pain. This economic burden is greater than annual costs associated with heart disease, cancer, and diabetes combined. Treatment options for chronic pain are inadequately efficacious and riddled with adverse side effects. There is thus an urgent unmet need for novel approaches to treating chronic pain. Sensitization of neurons along the nociceptive pathway causes chronic pain states driving symptoms that include spontaneous pain and mechanical and thermal hypersensitivity. More than a decade of preclinical research demonstrates that translational mechanisms regulate the changes in gene expression that are required for ongoing sensitization of nociceptive sensory neurons. This review will describe how key translation regulation signaling pathways, including the integrated stress response, mammalian target of rapamycin, AMP-activated protein kinase (AMPK), and mitogen-activated protein kinase-interacting kinases, impact the translation of different subsets of mRNAs. We then place these mechanisms of translation regulation in the context of chronic pain states, evaluate currently available therapies, and examine the potential for developing novel drugs. Considering the large body of evidence now published in this area, we propose that pharmacologically manipulating specific aspects of the translational machinery may reverse key neuronal phenotypic changes causing different chronic pain conditions. Therapeutics targeting these pathways could eventually be first-line drugs used to treat chronic pain disorders. SIGNIFICANCE STATEMENT: Translational mechanisms regulating protein synthesis underlie phenotypic changes in the sensory nervous system that drive chronic pain states. This review highlights regulatory mechanisms that control translation initiation and how to exploit them in treating persistent pain conditions. We explore the role of mammalian/mechanistic target of rapamycin and mitogen-activated protein kinase-interacting kinase inhibitors and AMPK activators in alleviating pain hypersensitivity. Modulation of eukaryotic initiation factor 2α phosphorylation is also discussed as a potential therapy. Targeting specific translation regulation mechanisms may reverse changes in neuronal hyperexcitability associated with painful conditions.

The Sigma-2 receptor / transmembrane protein 97 (σ2R/TMEM97) modulator JVW-1034 reduces heavy alcohol drinking and associated pain states in male mice.

Alcohol Use Disorder (AUD) is a chronic relapsing disorder characterized by compulsive alcohol intake, loss of control over alcohol intake, and a negative emotional state when access to alcohol is prevented. AUD is also closely tied to pain, as repeated alcohol drinking leads to increased pain sensitivity during withdrawal. The sigma-2 receptor, recently identified as transmembrane protein 97 (σ2R/TMEM97), is an integral membrane protein involved in cholesterol homeostasis and lipid metabolism. Selective σ2R/Tmem97 modulators have been recently shown to relieve mechanical hypersensitivity in animal models of neuropathic pain as well as to attenuate alcohol withdrawal signs in C. elegans and to reduce alcohol drinking in rats, suggesting a potential key role for this protein in alcohol-related behaviors. In this study, we tested the effects of a potent and selective σ2R/TMEM97 ligand, JVW-1034, on heavy alcohol drinking and alcohol-induced heightened pain states in mice using an intermittent access model. Administration of JVW-1034 decreased both ethanol intake and preference for ethanol, without affecting water intake, total fluid intake, or food intake. Notably, this effect was specific for alcohol, as JVW-1034 had no effect on sucrose intake. Furthermore, JVW-1034 reduced both thermal hyperalgesia and mechanical hypersensitivity in ethanol withdrawn mice. Our data provide important evidence that modulation of σ2R/TMEM97 with small molecules can mediate heavy alcohol drinking as well as chronic alcohol-induced heightened pain sensitivity, thereby identifying a promising novel pharmacological target for AUD and associated pain states.

Neuroprotective Efficacy of a Sigma 2 Receptor/TMEM97 Modulator (DKR-1677) after Traumatic Brain Injury.

Compounds targeting the sigma 2 receptor, which we recently cloned and showed to be identical with transmembrane protein 97 (σ2R/TMEM97), are broadly applicable therapeutic agents currently in clinical trials for imaging in breast cancer and for treatment of Alzheimer's disease and schizophrenia. These promising applications coupled with our previous observation that the σ2R/TMEM97 modulator SAS-0132 has neuroprotective attributes and improves cognition in wild-type mice suggests that modulating σ2R/TMEM97 may also have therapeutic benefits in other neurodegenerative conditions such as traumatic brain injury (TBI). Herein, we report that DKR-1677, a novel derivative of SAS-0132 with increased affinity and selectivity for σ2R/Tmem97 ( Ki = 5.1 nM), is neuroprotective after blast-induced and controlled cortical impact (CCI) TBI in mice. Specifically, we discovered that treatment with DKR-1677 decreases axonal degeneration after blast-induced TBI and enhances survival of cortical neurons and oligodendrocytes after CCI injury. Furthermore, treatment with DKR-1677 preserves cognition in the Morris water maze after blast TBI. Our results support an increasingly broad role for σ2R/Tmem97 modulation in neuroprotection and suggest a new approach for treating patients suffering from TBI.

Small molecule modulators of σ2R/Tmem97 reduce alcohol withdrawal-induced behaviors.

Repeated cycles of intoxication and withdrawal enhance the negative reinforcing properties of alcohol and lead to neuroadaptations that underlie withdrawal symptoms driving alcohol dependence. Pharmacotherapies that target these neuroadaptations may help break the cycle of dependence. The sigma-1 receptor (σ1R) subtype has attracted interest as a possible modulator of the rewarding and reinforcing effects of alcohol. However, whether the sigma-2 receptor, recently cloned and identified as transmembrane protein 97 (σ2R/TMEM97), plays a role in alcohol-related behaviors is currently unknown. Using a Caenorhabditis elegans model, we identified two novel, selective σ2R/Tmem97 modulators that reduce alcohol withdrawal behavior via an ortholog of σ2R/TMEM97. We then show that one of these compounds blunted withdrawal-induced excessive alcohol drinking in a well-established rodent model of alcohol dependence. These discoveries provide the first evidence that σ2R/TMEM97 is involved in alcohol withdrawal behaviors and that this receptor is a potential new target for treating alcohol use disorder.

Investigating isoindoline, tetrahydroisoquinoline, and tetrahydrobenzazepine scaffolds for their sigma receptor binding properties.

Substituted norbenzomorphans are known to display high affinity and selectivity for the two sigma receptor (σR) subtypes. In order to study the effects of simplifying the structures of these compounds, a scaffold hopping strategy was used to design several novel sets of substituted isoindolines, tetrahydroisoquinolines and tetrahydro-2-benzazepines. The binding affinities of these new compounds for the sigma 1 (σ1R) and sigma 2 (σ2R) receptors were determined, and some analogs were identified that exhibit high affinity (Ki ≤ 25 nM) and significant selectivity (>10-fold) for σ1R or σ2R. The preferred binding modes of selected compounds for the σ1R are predicted by modeling studies, and the nature of substituents on the aromatic ring and the nitrogen atom of the bicyclic skeleton appears to affect the preferred binding orientation of σ1R-preferring ligands.

High-Content Microfluidic Screening Platform Used To Identify σ2R/Tmem97 Binding Ligands that Reduce Age-Dependent Neurodegeneration in C. elegans SC_APP Model.

The nematode Caenorhabditis elegans, with tractable genetics and a well-defined nervous system, provides a unique whole-animal model system to identify novel drug targets and therapies for neurodegenerative diseases. Large-scale drug or target screens in models that recapitulate the subtle age- and cell-specific aspects of neurodegenerative diseases are limited by a technological requirement for high-throughput analysis of neuronal morphology. Recently, we developed a single-copy model of amyloid precursor protein (SC_APP) induced neurodegeneration that exhibits progressive degeneration of select cholinergic neurons. Our previous work with this model suggests that small molecule ligands of the sigma 2 receptor (σ2R), which was recently cloned and identified as transmembrane protein 97 (TMEM97), are neuroprotective. To determine structure-activity relationships for unexplored chemical space in our σ2R/Tmem97 ligand collection, we developed an in vivo high-content screening (HCS) assay to identify potential drug leads. The HCS assay uses our recently developed large-scale microfluidic immobilization chip and automated imaging platform. We discovered norbenzomorphans that reduced neurodegeneration in our C. elegans model, including two compounds that demonstrated significant neuroprotective activity at multiple doses. These findings provide further evidence that σ2R/Tmem97-binding norbenzomorphans may represent a new drug class for treating neurodegenerative diseases.

Sigma 2 Receptor/Tmem97 Agonists Produce Long Lasting Antineuropathic Pain Effects in Mice.

Neuropathic pain is an important medical problem with few effective treatments. The sigma 1 receptor (σ1R) is known to be a potential target for neuropathic pain therapeutics, and antagonists for this receptor are effective in preclinical models and are currently in phase II clinical trials. Conversely, relatively little is known about σ2R, which has recently been identified as transmembrane protein 97 (Tmem97). We generated a series of σ1R and σ2R/Tmem97 agonists and antagonists and tested them for efficacy in the mouse spared nerve injury (SNI) model. In agreement with previous reports, we find that σ1R ligands given intrathecally (IT) produce relief of SNI-induced mechanical hypersensitivity. We also find that the putative σ2R/Tmem97 agonists DKR-1005, DKR-1051, and UKH-1114 (Ki ∼ 46 nM) lead to relief of SNI-induced mechanical hypersensitivity, peaking at 48 h after dosing when given IT. This effect is blocked by the putative σ2R/Tmem97 antagonist SAS-0132. Systemic administration of UKH-1114 (10 mg/kg) relieves SNI-induced mechanical hypersensitivity for 48 h with a peak magnitude of effect equivalent to 100 mg/kg gabapentin and without producing any motor impairment. Finally, we find that the TMEM97 gene is expressed in mouse and human dorsal root ganglion (DRG) including populations of neurons that are involved in pain; however, the gene is also likely expressed in non-neuronal cells that may contribute to the observed behavioral effects. Our results show robust antineuropathic pain effects of σ1R and σ2R/Tmem97 ligands, demonstrate that σ2R/Tmem97 is a novel neuropathic pain target, and identify UKH-1114 as a lead molecule for further development.

Identification of the gene that codes for the σ2 receptor.

The σ2 receptor is an enigmatic protein that has attracted significant attention because of its involvement in diseases as diverse as cancer and neurological disorders. Unlike virtually all other receptors of medical interest, it has eluded molecular cloning since its discovery, and the gene that codes for the receptor remains unknown, precluding the use of modern biological methods to study its function. Using a chemical biology approach, we purified the σ2 receptor from tissue, revealing its identity as TMEM97, an endoplasmic reticulum-resident transmembrane protein that regulates the sterol transporter NPC1. We show that TMEM97 possesses the full suite of molecular properties that define the σ2 receptor, and we identify Asp29 and Asp56 as essential for ligand recognition. Cloning the σ2 receptor resolves a longstanding mystery and will enable therapeutic targeting of this potential drug target.

Norbenzomorphan Scaffold: Chemical Tool for Modulating Sigma Receptor-Subtype Selectivity.

Some norbenzomorphans exhibit high affinity for sigma 1 and sigma 2 receptors, and varying the position of substituents on the aromatic ring of this scaffold has a significant effect on subtype selectivity. In particular, compounds bearing several different substituents at C7 of the norbenzomorphan ring system exhibit a general preference for the sigma 1 receptor, whereas the corresponding C8-substituted analogues preferentially bind at the sigma 2 receptor. These findings suggest that the norbenzomorphan scaffold may be a unique chemical template that can be easily tuned to prepare small molecules for use as tool compounds to study the specific biological effects arising from preferential binding at either sigma receptor subtype. In the absence of structural characterization data for the sigma 2 receptor, such compounds will be useful toward refining the pharmacophore model of its binding site.

Small molecule modulator of sigma 2 receptor is neuroprotective and reduces cognitive deficits and neuroinflammation in experimental models of Alzheimer's disease.

Accumulating evidence suggests that modulating the sigma 2 receptor (Sig2R) can provide beneficial effects for neurodegenerative diseases. Herein, we report the identification of a novel class of Sig2R ligands and their cellular and in vivo activity in experimental models of Alzheimer's disease (AD). We report that SAS-0132 and DKR-1051, selective ligands of Sig2R, modulate intracellular Ca2+ levels in human SK-N-SH neuroblastoma cells. The Sig2R ligands SAS-0132 and JVW-1009 are neuroprotective in a C. elegans model of amyloid precursor protein-mediated neurodegeneration. Since this neuroprotective effect is replicated by genetic knockdown and knockout of vem-1, the ortholog of progesterone receptor membrane component-1 (PGRMC1), these results suggest that Sig2R ligands modulate a PGRMC1-related pathway. Last, we demonstrate that SAS-0132 improves cognitive performance both in the Thy-1 hAPPLond/Swe+ transgenic mouse model of AD and in healthy wild-type mice. These results demonstrate that Sig2R is a promising therapeutic target for neurocognitive disorders including AD.

Norbenzomorphan Framework as a Novel Scaffold for Generating Sigma†2 Receptor/PGRMC1 Subtype-Selective Ligands.

A novel structural class with high affinity and subtype selectivity for the sigma 2 receptor has been discovered. Preliminary structure-affinity relationship data are presented showing that 8-substituted 1,3,4,5-tetrahydro-1,5-methanobenzazepine (norbenzomorphan) derivatives elicit modest to high selectivity for the sigma 2 over the sigma 1 receptor subtype. Indeed, piperazine analogue 8-(4-(3-ethoxy-3-oxopropyl)piperazin-1-yl)-1,3,4,5-tetrahydro-1,5-methanobenzazepine-2-carboxylate (SAS-1121) is 574-fold selective for the sigma 2 over the sigma 1 receptor, thereby establishing it as one of the more subtype-selective sigma 2 binding ligands reported to date. Emerging evidence has implicated the sigma 2 receptor in multiple health disorders, so the drug-like characteristics of many of the selective sigma 2 receptor ligands disclosed herein, coupled with their structural similarity to frameworks found in known drugs, suggest that norbenzomorphan analogues may be promising candidates for further development into drug leads.

Evolution of a strategy for preparing bioactive small molecules by sequential multicomponent assembly processes, cyclizations, and diversification.

A strategy for generating diverse collections of small molecules has been developed that features a multicomponent assembly process (MCAP) to efficiently construct a variety of intermediates possessing an aryl aminomethyl subunit. These key compounds are then transformed via selective ring-forming reactions into heterocyclic scaffolds, each of which possesses suitable functional handles for further derivatizations and palladium-catalyzed cross coupling reactions. The modular nature of this approach enables the facile construction of libraries of polycyclic compounds bearing a broad range of substituents and substitution patterns for biological evaluation. Screening of several compound libraries thus produced has revealed a large subset of compounds that exhibit a broad spectrum of medicinally-relevant activities.

Expedient synthesis of norbenzomorphan library via multicomponent assembly process coupled with ring-closing reactions.

A 124-member norbenzomorphan library has been prepared utilizing a novel multicomponent assembly process (MCAP) followed by a variety of ring-closing reactions to generate norbenzomorphan scaffolds that were readily derivatized via a series of aryl halide cross-coupling and nitrogen functionalization reactions. Biological screening has revealed some novel activities that have not been previously associated with this class of compounds.