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A platform to accelerate optimization of proteolysis targeting chimeras (PROTACs) has been developed using a direct-to-biology (D2B) approach with a focus on linker effects. A large number of linker analogs-with varying length, polarity, and rigidity-were rapidly prepared and characterized in four cell-based assays by streamlining time-consuming steps in synthesis and purification. The expansive dataset informs on linker structure-activity relationships (SAR) for in-cell E3 ligase target engagement, degradation, permeability, and cell toxicity. Unexpected aspects of linker SAR was discovered, consistent with literature reports on "linkerology", and the method dramatically speeds up empirical optimization. Physicochemical property trends emerged, and the platform has the potential to rapidly expand training sets for more complex prediction models. In-depth validation studies were carried out and confirm the D2B platform is a valuable tool to accelerate PROTAC design-make-test cycles.

A novel series of histone deacetylase (HDAC) inhibitors lacking a zinc-binding moiety has been developed and described herein. HDAC isozyme profiling and kinetic studies indicate that these inhibitors display a selectivity preference for HDACs 1, 2, 3, 10, and 11 via a rapid equilibrium mechanism, and crystal structures with HDAC2 confirm that these inhibitors do not interact with the catalytic zinc. The compounds are nonmutagenic and devoid of electrophilic and mutagenic structural elements and exhibit off-target profiles that are promising for further optimization. The efficacy of this new class in biochemical and cell-based assays is comparable to the marketed HDAC inhibitors belinostat and vorinostat. These results demonstrate that the long-standing pharmacophore model of HDAC inhibitors requiring a metal binding motif should be revised and offers a distinct class of HDAC inhibitors.

[Image: see text] The selectivity of histone deacetylase inhibitors (HDACis) is greatly impacted by the zinc binding groups. In an effort to search for novel zinc binding groups, we applied a parallel medicinal chemistry (PMC) strategy to quickly synthesize substituted benzamide libraries. We discovered a series containing 2-substituted benzamides as the zinc binding group which afforded highly selective and potent HDAC3 inhibitors, exemplified by compound 16 with a 2-methylthiobenzamide. Compound 16 inhibited HDAC3 with an IC(50) of 30 nM and with unprecedented selectivity of >300-fold over all other HDAC isoforms. Interestingly, a subtle change of the 2-methylthio to a 2-hydroxy benzamide in 20 retains HDAC3 potency but loses all selectivity over HDAC 1 and 2. This significant difference in selectivity was rationalized by X-ray crystal structures of HDACis 16 and 20 bound to HDAC2, revealing different binding modes to the catalytic zinc ion. This series of HDAC3 selective inhibitors served as tool compounds for investigating the minimal set of HDAC isoforms that must be inhibited for the HIV latency activation in a Jurkat 2C4 cell model and potentially as leads for selective HDAC3 inhibitors for other indications.

[Image: see text] DNA-encoded library (DEL) screens have emerged as a powerful hit-finding tool for a number of biological targets. In this Innovations article, we review published hit-to-lead optimization studies following DEL screens. Trends in molecular property changes from hit to lead are identified, and specific optimization tactics are exemplified in case studies. Across the studies, physicochemical property and structural changes post-DEL screening are similar to those which occur during hit-to-lead optimization following high throughputscreens (HTS). However, unique aspects of DEL—the combinatorial synthetic methods which enable DEL synthesis and the linker effects at the DNA attachment point—impact the strategies and outcomes of hit-to-lead optimizations.

[Image: see text] By employing a phenotypic screen, a set of compounds, exemplified by 1, were identified which potentiate the ability of histone deacetylase inhibitor vorinostat to reverse HIV latency. Proteome enrichment followed by quantitative mass spectrometric analysis employing a modified analogue of 1 as affinity bait identified farnesyl transferase (FTase) as the primary interacting protein in cell lysates. This ligand-FTase binding interaction was confirmed via X-ray crystallography and temperature dependent fluorescence studies, despite 1 lacking structural and binding similarity to known FTase inhibitors. Although multiple lines of evidence established the binding interaction, these ligands exhibited minimal inhibitory activity in a cell-free biochemical FTase inhibition assay. Subsequent modification of the biochemical assay by increasing anion concentration demonstrated FTase inhibitory activity in this novel class. We propose 1 binds together with the anion in the active site to inhibit farnesyl transferase. Implications for phenotypic screening deconvolution and HIV reactivation are discussed.

Studies on human genetics have suggested that inhibitors of the Nav1.7 voltage-gated sodium channel hold considerable promise as therapies for the treatment of chronic pain syndromes. Herein, we report novel, peripherally-restricted benzoxazolinone aryl sulfonamides as potent Nav1.7 inhibitors with excellent selectivity against the Nav1.5 isoform, which is expressed in the heart muscle. Elaboration of initial lead compound 3d afforded exemplar 13, which featured attractive physicochemical properties, outstanding lipophilic ligand efficiency and pharmacological selectivity against Nav1.5 exceeding 1000-fold. Key structure-activity relationships associated with oral bioavailability were leveraged to discover compound 17, which exhibited a comparable potency/selectivity profile as well as full efficacy following oral administration in a preclinical model indicative of antinociceptive behavior.

[Image: see text] Access to high quality photoaffinity probe molecules is often constrained by synthetic limitations related to diazirine installation. A survey of recently published photoaffinity probe syntheses identified the Suzuki–Miyaura (S–M) coupling reaction, ubiquitous in drug discovery, as being underutilized to incorporate diazirines. To test whether advances in modern cross-coupling catalysis might enable efficient S–M couplings tolerant of the diazirine moiety, a fragment-based screening approach was employed. A model S–M coupling reaction was screened under various conditions in the presence of an aromatic diazirine fragment. This screen identified reaction conditions that gave good yields of S–M coupling product while minimally perturbing the diazirine reporter fragment. These conditions were found to be highly scalable and exhibited broad scope when applied to a chemistry informer library of 24 pharmaceutically relevant aryl boron pinacol esters. Furthermore, these conditions were used to synthesize a known diazirine-containing probe molecule with improved synthetic efficiency.

3-Hydroxy-4-pyridinones and 5-hydroxy-4-pyrimidinones were identified as inhibitors of catechol-O-methyltransferase (COMT) in a high-throughput screen. These heterocyclic catechol mimics exhibit potent inhibition of the enzyme and an improved toxicity profile versus the marketed nitrocatechol inhibitors tolcapone and entacapone. Optimization of the series was aided by X-ray cocrystal structures of the novel inhibitors in complex with COMT and cofactors SAM and Mg(2+). The crystal structures suggest a mechanism of inhibition for these heterocyclic inhibitors distinct from previously disclosed COMT inhibitors.

Studies on human genetics have suggested that inhibitors of the Na

Selective inhibition of Kv1.5, which underlies the ultra-rapid delayed rectifier current, IKur, has been pursued as a treatment for atrial fibrillation. Here we describe the discovery of MK-1832, a Kv1.5 inhibitor with improved selectivity versus the off-target current IKs, whose inhibition has been associated with ventricular proarrhythmia. MK-1832 exhibits improved selectivity for IKur over IKs (>3000-fold versus 70-fold for MK-0448), consistent with an observed larger window between atrial and ventricular effects in vivo (>1800-fold versus 210-fold for MK-0448). MK-1832 also exhibits an improved preclinical pharmacokinetic profile consistent with projected once daily dosing in humans.

A series of N -heterocyclic pyridinone catechol- O -methyltransferase (COMT) inhibitors were synthesized. Physicochemical properties, including ligand lipophilic efficiency (LLE) and c log P , were used to guide compound design and attempt to improve inhibitor pharmacokinetics. Incorporation of heterocyclic central rings provided improvements in physicochemical parameters but did not significantly reduce in vitro or in vivo clearance. Nevertheless, compound 11 was identified as a potent inhibitor with sufficient in vivo exposure to significantly affect the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), and indicate central COMT inhibition.

Reduced dopamine neurotransmission in the prefrontal cortex has been implicated as causal for the negative symptoms and cognitive deficit associated with schizophrenia; thus, a compound which selectively enhances dopamine neurotransmission in the prefrontal cortex may have therapeutic potential. Inhibition of catechol-O-methyltransferase (COMT, EC 2.1.1.6) offers a unique advantage, since this enzyme is the primary mechanism for the elimination of dopamine in cortical areas. Since membrane bound COMT (MB-COMT) is the predominant isoform in human brain, a high throughput screen (HTS) to identify novel MB-COMT specific inhibitors was completed. Subsequent optimization led to the identification of novel, non-nitrocatechol COMT inhibitors, some of which interact specifically with MB-COMT. Compounds were characterized for in vitro efficacy versus human and rat MB and soluble (S)-COMT. Select compounds were administered to male Wistar rats, and ex vivo COMT activity, compound levels in plasma and cerebrospinal fluid (CSF), and CSF dopamine metabolite levels were determined as measures of preclinical efficacy. Finally, novel non-nitrocatechol COMT inhibitors displayed less potent uncoupling of the mitochondrial membrane potential (MMP) compared to tolcapone as well as nonhepatotoxic entacapone, thus mitigating the risk of hepatotoxicity.

Agonists of somatostatin receptor subtype 2 (sst(2)) have been proposed as therapeutics for the treatment of proliferative diabetic retinopathy and exudative age-related macular degeneration. An HTS screen identified 2-quinolones as weak agonists of sst(2), and these were optimized to provide small molecules with sst(2) binding and functional potency comparable to peptide agonists. Agonist 21 was shown to inhibit rat growth hormone secretion following systemic administration and to inhibit ocular neovascular lesion formation after local administration.

Glycine transporter 1 (GlyT1) represents a novel target for the treatment of schizophrenia via the potentiation of glutamatergic NMDA receptors. The discovery of 4,4-disubstituted piperidine inhibitors of GlyT1 which exhibit improved pharmacokinetic properties, including oral bioavailability, is discussed.

Straightforward procedures for the derivatization of tri- and tetrahalogenated quinolines utilizing sequential selective Pd-catalyzed cross-coupling reactions are described. Taking advantage of intrinsic halide reactivity, substrate control, and appropriate reaction conditions, highly selective reactions at the quinoline 3-, 4-, and 6-position are possible.

The preparation of oxazole-4-carboxamides and their subsequent thermal rearrangement to 5-aminooxazole-4-carboxylates is optimized in a high-speed microwave-assisted procedure. The reaction sequence is effective with a variety of substituted oxazoles, and produces products in good yield and high purity.

This article describes recent progress towards validation of the N-methyl-D-aspartate (NMDA) receptor hypofunction hypothesis of schizophrenia in preclinical models. Schizophrenia, a complex disease characterized by positive, negative and cognitive symptoms, affects 1% of the world population and requires lifelong, daily maintenance therapy. For the last several decades, thinking in this field has been dominated by the hypothesis that hyperfunction of dopamine pathways played a key role in schizophrenia. However, the therapeutic agents developed from this hypothesis have a slow onset of action and tend to improve only the positive symptoms of the disease. The NMDA receptor antagonist PCP has been shown to induce the positive, negative and cognitive symptoms of schizophrenia in healthy patients and cause a resurgence of symptoms in stable patients. These observations led to the NMDA receptor hypofunction hypothesis as an alternative theory for the underlying cause of schizophrenia. According to this hypothesis, any agent that can potentiate NMDA receptor currents has the potential to ameliorate the symptoms of schizophrenia. To date, NMDA receptor currents can be modulated by either direct action on modulatory sites on the NMDA receptor (i.e., the glycine co-agonist binding site) or indirectly by activation of G-protein coupled receptors (GPCRs) known to potentiate NMDA receptor function (i.e., mGluR5). This review will discuss the NMDA receptor hypofunction hypothesis, the NMDA receptor as an emerging target for the development of novel antipsychotic agents and progress towards in vivo target validation with GlyT1 inhibitors and mGluR5 positive allosteric modulators. Other potential targets for modulating NMDA receptor currents (polyamine sites, muscarinic receptors, etc...) will also be addressed briefly.

Yatakemycin represents the newest and now most potent member of a class of naturally occurring antitumor compounds that includes CC-1065 and the duocarmycins, which derive their biological properties from a characteristic DNA alkylation reaction. Herein, the first description of the yatakemycin DNA alkylation properties is detailed, constituting the first such study of a naturally occurring "sandwiched" member of this class. Thus, the event, sequence selectivity, relative rate and efficiency, and reversibility of the DNA alkylation reaction of yatakemycin are described.

Microwave-assisted organic synthesis (MAOS) addresses the need for accelerated chemical synthesis by providing many advantages over classical thermal conditions. Microwave instruments produced by Biotage, CEM and Milestone enable chemistry to be safely and reproducibly performed on various scales and in a parallel fashion. To illustrate the high utility of this technology for lead development, our Akt kinase program will be described wherein MAOS played a pivotal role in the identification of isozyme-selective Akt inhibitors.

The synthesis and examination of a novel class of reversed CPyI analogues of CC-1065 and the duocarmycins are described. Capable of a unique metal cation activation of DNA alkylation, these agents allowed the effects of the DNA binding domain (10(4)-fold increase in DNA alkylation rate and efficiency) to be partitioned into two components: that derived from enhanced DNA binding affinity and selectivity (10-80-fold) and that derived from a contribution to catalysis (250-5000-fold). In addition, the reversed enantiomeric selectivity of these sequence selective DNA alkylating agents provides further strong support for a previously disclosed model where it is the noncovalent binding selectivity of the compounds, and not the alkylation subunit or the source of catalysis, that controls the DNA alkylation selectivity.

Convergent total syntheses of anhydrolycorinone, hippadine, and anhydrolycorinium chloride are detailed, enlisting sequential inverse electron demand Diels-Alder reactions of an unsymmetrical N-acyl-6-amino-1,2,4,5-tetrazine.

The synthesis of 1,2,8,8a-tetrahydrocyclopropa[c]pyrrolo[3, 2-e]indol-4(5H)-one (CPI), the parent CC-1065 and duocarmycin SA alkylation subunit, is detailed. The parent CPI alkylation subunit lacks the C7 methyl substituent of the CC-1065 alkylation subunit and the C6 methoxycarbonyl group of duocarmycin SA, and their examination permitted the establishment of the impact of these natural product substituents. The studies revealed a CPI stability comparable to the CC-1065 alkylation subunit but which was 6x more reactive than the (+)-duocarmycin SA alkylation subunit, and it displayed the inherent reaction regioselectivity (4:1) of the natural products. The single-crystal X-ray structure of (+)-N-BOC-CPI depicts a near identical stereoelectronic alignment of the cyclopropane accounting for the identical reaction regioselectivity and a slightly diminished vinylogous amide conjugation relative to (+)-N-BOC-DSA suggesting that the stability distinctions stem in part from this difference in the vinylogous amide as well as alterations in the electronic nature of the fused pyrrole. Establishment of the DNA binding properties revealed that the CPI-based agents retain the identical DNA alkylation selectivities of the natural products. More importantly, the C6 methoxycarbonyl group of duocarmycin SA was found to increase the rate (12-13x) and efficiency (10x) of DNA alkylation despite its intrinsic lower reactivity while the CC-1065 C7 methyl group was found to slow the DNA alkylation rate (4x) and lower the alkylation efficiency (ca. 4x). The greater DNA alkylation rate and efficiency for duocarmycin SA and related analogues containing the C6 methoxycarbonyl is proposed to be derived from the extended length that the rigid C6 methoxycarbonyl provides and the resulting increase in the DNA binding-induced conformational change which serves to deconjugate the vinylogous amide and activate the alkylation subunit for nucleophilic attack. The diminished properties resulting from the CC-1065 C7 methyl group may be attributed to the steric impediment this substituent introduces to DNA minor groove binding and alkylation. Consistent with this behavior, the duocarmycin SA C6 methoxycarbonyl group increases biological potency while the CC-1065 C7 methyl group diminishes it.

The design, synthesis, and evaluation of a predictably more potent analogue of CC-1065 entailing the substitution replacement of a single skeleton atom in the alkylation subunit are disclosed and were conducted on the basis of design principles that emerged from a fundamental parabolic relationship between chemical reactivity and cytotoxic potency. Consistent with projections, the 7-methyl-1,2,8,8a-tetrahydrocyclopropa[c]thieno[3,2-e]indol-4-one (MeCTI) alkylation subunit and its isomer 6-methyl-1,2,8,8a-tetrahydrocyclopropa[c]thieno[2,3-e]indol-4-one (iso-MeCTI) were found to be 5-6 times more stable than the MeCPI alkylation subunit found in CC-1065 and slightly more stable than even the DSA alkylation subunit found in duocarmycin SA, placing it at the point of optimally balanced stability and reactivity for this class of antitumor agents. Their incorporation into the key analogues of the natural products provided derivatives that surpassed the potency of MeCPI derivatives (3-10-fold), matching or slightly exceeding the potency of the corresponding DSA derivatives, consistent with projections made on the basis of the parabolic relationship. Notable of these, MeCTI-TMI proved to be as potent as or slightly more potent than the natural product duocarmycin SA (DSA-TMI, IC50 = 5 vs 8 pM), and MeCTI-PDE2 proved to be 3-fold more potent than the natural product CC-1065 (MeCPI-PDE2, IC50 = 7 vs 20 pM). Both exhibited efficiencies of DNA alkylation that correlate with this enhanced potency without impacting the intrinsic selectivity characteristic of this class of antitumor agents.

5-Fluoro-2-aryloxazolo[5,4-b]pyridines were synthesized and investigated as potential (18)F containing β-amyloid PET ligands. In competition binding assays using human AD brain homogenates, compounds 14b, 16b, and 17b were identified as having favorable potency versus human β-amyloid plaque and were radiolabeled for further evaluation in in vitro binding and in vivo PET imaging experiments. These studies led to the identification of 17b (MK-3328) as a candidate PET ligand for the clinical assessment of β-amyloid plaque load.

Introduction An 18 F-labeled positron emission tomography (PET) tracer for amyloid plaque is desirable for early diagnosis of Alzheimer's disease, particularly to enable preventative treatment once effective therapeutics are available. Similarly, such a tracer would be useful as a biomarker for enrollment of patients in clinical trials for evaluation of antiamyloid therapeutics. Furthermore, changes in the level of plaque burden as quantified by an amyloid plaque PET tracer may provide valuable insights into the effectiveness of amyloid-targeted therapeutics. This work describes our approach to evaluate and select a candidate PET tracer for in vivo quantification of human amyloid plaque. Methods Ligands were evaluated for their in vitro binding to human amyloid plaques, lipophilicity and predicted blood–brain barrier permeability. Candidates with favorable in vitro properties were radiolabeled with 18 F and evaluated in vivo. Baseline PET scans in rhesus monkey were conducted to evaluate the regional distribution and kinetics of each tracer using tracer kinetic modeling methods. High binding potential in cerebral white matter and cortical grey matter was considered an unfavorable feature of the candidate tracers. Results [ 18 F]MK-3328 showed the most favorable combination of low in vivo binding potential in white matter and cortical grey matter in rhesus monkeys, low lipophilicity (Log D=2.91) and high affinity for human amyloid plaques (IC 50 =10.5±1.3 nM). Conclusions [ 18 F]MK-3328 was identified as a promising PET tracer for in vivo quantification of amyloid plaques, and further evaluation in humans is warranted.

The Merck Fragment Library was screened versus acid-sensing ion channel 3 (ASIC3), a novel target for the treatment of pain. Fragment hits were optimized using two strategies, and potency was improved from 0.7 mM to 3 μM with retention of good ligand efficiency and incorporation of reasonable physical properties, off-target profile, and rat pharmacokinetics.

The simple amino acid glycine is implicated in both inhibitory and excitatory neurotransmission in mammalian central nervous system, and it modulates excitatory neurotransmission through its role as a necessary co-agonist for glutamatergic N-methyl-D-aspartate (NMDA) receptors. Given the involvement of NMDA receptor-mediated neurotransmission in complex cerebral processes such as cognition, pharmacological manipulation of extracellular synaptic glycine biology is an active area of pharmaceutical research to develop novel treatments for neuropsychiatric disorders. A key component of cerebral glycine metabolism is the glycine transporter type 1 (GlyT1) and elevation of extracellular synaptic glycine concentration by blockade of GlyT1 has been hypothesized to potentiate NMDA receptor function in vivo and to represent a rational approach for the treatment of schizophrenia and cognitive disorders. The present article will review the wealth of scientific evidence supporting that hypothesis and the medicinal chemistry effort by many pharmaceutical companies and academic institutions to develop potent and selective GlyT1 inhibitors.

Employing an iterative analogue library approach, novel potent and selective glycine transporter 1 (GlyT1) inhibitors containing a 4-pyridin-2-ylpiperidine sulfonamide have been discovered. These inhibitors are devoid of time-dependent CYP inhibition activity and exhibit improved aqueous solubility versus the corresponding 4-phenylpiperidine analogues.

Straightforward procedures for the derivatization of tri- and tetrahalogenated quinolines utilizing sequential selective Pd-catalyzed cross-coupling reactions are described. Taking advantage of intrinsic halide reactivity, substrate control, and appropriate reaction conditions, highly selective reactions at the quinoline 3-, 4-, and 6-position are possible.

Over the past 5 years, researchers in industry and academia have reported the design, synthesis and evaluation of many non-peptide ligands for somatostatin receptors. Structurally diverse agonists and antagonists that, in some cases, exhibit selectivity among the somatostatin receptor subtypes have been published. These agents represent research tools for the clarification of individual receptor pharmacology and are also promising leads for the development of orally active therapeutics for endocrine disorders, proliferative diseases and mood disorders. This review summarizes recent developments in the identification of non-peptide ligands of somatostatin receptors.

This Letter describes the design, synthesis, and biological evaluation of novel 3-indole sulfonamides as potent non-nucleoside reverse transcriptase inhibitors (NNRTIs) with balanced profiles against common HIV RT mutants K103N and Y181C.

The total synthesis of cytostatin, an antitumor agent belonging to the fostriecin family of natural products, is disclosed. The convergent route features a key epoxide opening reaction to join the two stereotriad units and a single-step late stage, stereoselective installation of the sensitive triene through a β-chelation controlled nucleophilic addition. The synthesis provides rapid access to the C4-C6 and C 10-C 11 stereoisomers of cytostatin and additional analogues to define the substituent role in PP2A binding.

We have developed convenient and general MAOS protocols for the synthesis of functionalized 1,2,4-triazines, canthines, imidazoles, quinoxalines, pyrazines, quinoxalinones, and 5-aminooxazoles. The methodology described herein makes use of readily available building blocks, facilitating the generation of structurally diverse analog libraries to support nascent medicinal chemistry programs. Other advantages over classical heating conditions include shortened reaction times, increased yields, and the suppression of side product formation.

The total synthesis of cytostatin, an antitumor agent belonging to the fostriecin family of natural products, is described in full detail. The convergent approach relied on a key epoxide-opening reaction to join the two stereotriad units and a single-step late-stage stereoselective installation of the sensitive (Z,Z,E)-triene through a beta-chelation-controlled nucleophilic addition. The synthetic route provided rapid access to the C4-C6 stereoisomers of the cytostatin lactone, which were prepared and used to define the C4-C6 relative stereochemistry of the natural product. In addition to the natural product, each of the C10-C11 diastereomers of cytostatin was divergently prepared (11 steps from key convergence step) by this route and used to unequivocally confirm the relative and absolute stereochemistry of cytostatin. Each of the cytostatin diastereomers exhibited a reduced activity toward inhibition of PP2A (>100-fold), demonstrating the importance of the presence and stereochemistry of the C10-methyl and C11-hydroxy groups for potent PP2A inhibition. Extensions of the studies provided dephosphocytostatin, sulfocytostatin (a key analogue related to the natural product sultriecin), 11-deshydroxycytostatin, and an analogue lacking the entire C12-C18 (Z,Z,E)-triene segment, which were used to define the magnitude of the C9-phosphate (>4000-fold), C11-alcohol (250-fold), and triene (220-fold) contribution to PP2A inhibition. A model of cytostatin bound to the active site of PP2A is presented, compared to that of fostriecin, which is also presented in detail for the first time, and used to provide insights into the role of the key substituents. Notably, the alpha,beta unsaturated lactone of cytostatin, like that of fostriecin, is projected to serve as a key electrophile, providing a covalent adduct with Cys269 unique to PP2A, contributing to its potency (> or =200-fold for fostriecin) and accounting for its selectivity.

Clinically utilized antipsychotic agents share as a common mechanism the ability to antagonize dopamine D2 receptors and it is widely assumed that this activity contributes to their efficacy against the positive symptoms of schizophrenia. The efficacy of currently marketed antipsychotic agents on the negative and cognitive symptoms of this disease, however, is not optimal. One alternate hypothesis to the "dopamine hypothesis" of schizophrenia derives from the observation that antagonists of NMDA receptor activity better mimic the symptomatology of schizophrenia in its entirety than do dopamine agonists. Findings from this line of research have led to the NMDA receptor hypofunction (or glutamate dysfunction) hypothesis of schizophrenia, which complements existing research implicating dopamine dysfunction in the disease. According to the NMDA receptor hypofunction hypothesis, any treatment that enhances NMDA receptor activity may prove useful for the treatment of the complex symptoms that define schizophrenia. This idea is now supported by numerous clinical studies that have reported an efficacious response following treatment with activators of the NMDA receptor co-agonist glycineB site. One area of study, aimed at potentiating the NMDA receptor via activation of the glycineB site is small molecule blockade of the glycine reuptake transporter type 1 (GlyT1). Broadly, these efforts have focused on derivatives of the substrate inhibitor, sarcosine, and non-sarcosine based GlyT1 inhibitors. Accordingly, the following review discusses the development of both sarcosine and non-sarcosine based GlyT1 inhibitors and their current status as putative treatments for schizophrenia and other disorders associated with NMDA receptor hypoactivity.

This review presents a summary of reactions performed using microwave irradiation on a multigram scale. Results are described in the context of existing equipment, and equipment currently in development, for the processing of multigram to kilogram quantities of materials including single- and multimode microwave reactors and batch, batch-flow and continuous-flow systems. Although limited in number, reports found in the literature to date suggest that with appropriate controls, reproducible scale-up of microwave reactions is feasible and requires minimal re-optimization of laboratory-scale reaction conditions. This feature, along with the dramatic reductions in reaction time generally observed for microwave reactions suggests that application of this technology in process research could be beneficial.

This Letter describes the synthesis and SAR, developed through an iterative analog library approach, of potent and selective non-sarcosine-derived GlyT1 inhibitors.

Agonists of NR2E3 (PNR, RNR) have been identified and optimized to EC(50)< 200 nM. A tritiated analogue of one agonist was prepared to aid in the development of a binding assay.

This review presents a summary of reactions performed using microwave irradiation on a multigram scale. Results are described in the context of existing equipment, and equipment currently in development, for the processing of multigram to kilogram quantities of materials including single- and multimode microwave reactors and batch, batch-flow and continuous-flow systems. Although limited in number, reports found in the literature to date suggest that with appropriate controls, reproducible scale-up of microwave reactions is feasible and requires minimal re-optimization of laboratory-scale reaction conditions. This feature, along with the dramatic reductions in reaction time generally observed for microwave reactions suggests that application of this technology in process research could be beneficial.

Positive allosteric modulators of metabotropic glutamate receptors (mGluRs) are the subject of intensive research due to their emerging therapeutic potential for a range of psychiatric and neurological disorders such as pain, anxiety, cognition, Parkinson's disease and schizophrenia. Positive allosteric modulators, which are small molecules capable of enhancing agonist-mediated receptor activity while possessing no intrinsic agonist activity, have recently been described for group I (mGluR1 and mGluR5), group II (mGluR2) and group III (mGluR4) mGluRs. Relative to classical mGluR agonists, these molecules offer improved selectivity versus other mGluRs and chemical tractability, and may reduce the liability of receptor desensitization.

Functionalized quinoxalines and heterocyclic pyrazines are expediently prepared in excellent yields (69–99%) from common 1,2-diketone intermediates under microwave irradiation. In addition to being general for a variety of aryl/heteroaryl 1,2-diamines and 1,2-diketones, this protocol suppresses the formation of polymeric species, characteristic of traditional thermal conditions.

[reaction: see text] A simple, high-yielding synthesis of 2,4,5-trisubstituted imidazoles from 1,2-diketones and aldehydes in the presence of NH(4)OAc is described. Under microwave irradiation, alkyl-, aryl-, and heteroaryl-substituted imidazoles are formed in yields ranging from 80 to 99%. Short syntheses of lepidiline B and trifenagrel illustrate the utility of this approach.

The scope of intramolecular Diels-Alder and a novel tandem Diels-Alder/1,3-dipolar cycloaddition cascade of 1,3,4-oxadiazoles is disclosed. In the cases examined, the tandem cycloadditions construct three new rings with formation of four new C-C bonds and set all six stereocenters about a central six-membered ring in a single step including three contiguous and four total quaternary centers without a trace of a second diastereomer.

A convergent total synthesis of anhydrolycorinone is detailed, enlisting sequential intramolecular Diels−Alder reactions of a suitably substituted 2-amino-1,3,4-oxadiazole defining a novel oxadiazole → furan → benzene Diels−Alder strategy.

Convergent total syntheses of anhydrolycorinone, hippadine, and anhydrolycorinium chloride are detailed, enlisting sequential inverse electron demand Diels−Alder reactions of an unsymmetrical N-acyl-6-amino-1,2,4,5-tetrazine.