Publications

Two closely related binding modes have previously been proposed for the ATP-competitive benzimidazole class of checkpoint kinase 2 (CHK2) inhibitors; however, neither binding mode is entirely consistent with the reported SAR. Unconstrained rigid docking of benzimidazole ligands into representative CHK2 protein crystal structures reveals an alternative binding mode involving a water-mediated interaction with the hinge region; docking which incorporates protein side chain flexibility for selected residues in the ATP binding site resulted in a refinement of the water-mediated hinge binding mode that is consistent with observed SAR. The flexible docking results are in good agreement with the crystal structures of four exemplar benzimidazole ligands bound to CHK2 which unambiguously confirmed the binding mode of these inhibitors, including the water-mediated interaction with the hinge region, and which is significantly different from binding modes previously postulated in the literature.

Optimization of the imidazo[4,5-b]pyridine-based series of Aurora kinase inhibitors led to the identification of 6-chloro-7-(4-(4-chlorobenzyl)piperazin-1-yl)-2-(1,3-dimethyl-1H-pyrazol-4-yl)-3H-imidazo[4,5-b]pyridine (27e), a potent inhibitor of Aurora kinases (Aurora-A K(d) = 7.5 nM, Aurora-B K(d) = 48 nM), FLT3 kinase (K(d) = 6.2 nM), and FLT3 mutants including FLT3-ITD (K(d) = 38 nM) and FLT3(D835Y) (K(d) = 14 nM). FLT3-ITD causes constitutive FLT3 kinase activation and is detected in 20-35% of adults and 15% of children with acute myeloid leukemia (AML), conferring a poor prognosis in both age groups. In an in vivo setting, 27e strongly inhibited the growth of a FLT3-ITD-positive AML human tumor xenograft (MV4-11) following oral administration, with in vivo biomarker modulation and plasma free drug exposures consistent with dual FLT3 and Aurora kinase inhibition. Compound 27e, an orally bioavailable dual FLT3 and Aurora kinase inhibitor, was selected as a preclinical development candidate for the treatment of human malignancies, in particular AML, in adults and children.

Acquired resistance to selective FLT3 inhibitors is an emerging clinical problem in the treatment of FLT3-ITD(+) acute myeloid leukaemia (AML). The paucity of valid pre-clinical models has restricted investigations to determine the mechanism of acquired therapeutic resistance, thereby limiting the development of effective treatments. We generated selective FLT3 inhibitor-resistant cells by treating the FLT3-ITD(+) human AML cell line MOLM-13 in vitro with the FLT3-selective inhibitor MLN518, and validated the resistant phenotype in vivo and in vitro. The resistant cells, MOLM-13-RES, harboured a new D835Y tyrosine kinase domain (TKD) mutation on the FLT3-ITD(+) allele. Acquired TKD mutations, including D835Y, have recently been identified in FLT3-ITD(+) patients relapsing after treatment with the novel FLT3 inhibitor, AC220. Consistent with this clinical pattern of resistance, MOLM-13-RES cells displayed high relative resistance to AC220 and Sorafenib. Furthermore, treatment of MOLM-13-RES cells with AC220 lead to loss of the FLT3 wild-type allele and the duplication of the FLT3-ITD-D835Y allele. Our FLT3-Aurora kinase inhibitor, CCT137690, successfully inhibited growth of FLT3-ITD-D835Y cells in vitro and in vivo, suggesting that dual FLT3-Aurora inhibition may overcome selective FLT3 inhibitor resistance, in part due to inhibition of Aurora kinase, and may benefit patients with FLT3-mutated AML.

We describe a computational method, plane of best fit (PBF), to quantify and characterize the 3D character of molecules. This method is rapid and amenable to analysis of large diverse data sets. We compare PBF with alternative literature methods used to assess 3D character and apply the method to diverse data sets of fragment-like, drug-like, and natural product compound libraries. We show that exemplar fragment libraries underexploit the potential of 3D character in fragment-like chemical space and that drug-like molecules in the libraries examined are predominantly 2D in character.

Transforming growth factor-beta (TGF-beta) signalling plays a key role in colorectal cancer (CRC). Bone morphogenetic protein-4 (BMP4) is a member of the TGF-beta family of signal transduction molecules. To examine if germline mutation in BMP4 causes CRC we analysed 504 genetically enriched CRC cases (by virtue of early-onset disease, family history of CRC) for mutations in the coding sequence of BMP4. We identified three pathogenic mutations, p. R286X (g.8330C>T), p.W325C (g.8449G>T) and p.C373S (g.8592G>C), amongst the CRC cases which were not observed in 524 healthy controls. p. R286X localizes to the N-terminal of the TGF-beta 1 prodomain truncating the protein prior to the active domain. p.W325C and p.C373S mutations are predicted from protein homology modelling with BMP2 to impact deleteriously on BMP4 function. Segregation of p.C373S with adenoma and hyperplastic polyp in first-degree relatives of the case suggests germline mutations may confer a juvenile polyposis-type phenotype. These findings suggest mutation of BMP4 is a cause of CRC and the value of protein-based modelling in the elucidation of rare disease-causing variants. (C) 2010 Wiley-Liss, Inc.

Deregulation of protein kinases is associated with numerous diseases, making them important targets for drug discovery. The majority of drugs target the catalytic site of these proteins, but due to the high level of similarity within the ATP binding sites of protein kinases, it is often difficult to achieve the required pharmacological selectivity. In this study, we describe the identification and subsequent analysis of water patterns in the ATP binding sites of 171 protein kinase structures, comprising 19 different kinases from various branches of the kinome, and demonstrate that structurally similar binding sites often have significantly different water patterns. We show that the observed variations in water patterns of different, but structurally similar kinases can be exploited in the structure-based design of potent and selective kinase inhibitors. Proteins 2011; © 2011 Wiley-Liss, Inc.

New pyrimido[4,5-d]azepines 7 are disclosed as potent 5-HT(2C) receptor agonists. A preferred example, 7b had minimal activation at either the 5-HT(2A) or 5-HT(2B) receptors combined with robust efficacy in a preclinical canine model of stress urinary incontinence (SUI) and attractive pharmacokinetic and safety properties. Based on this profile, 7b (PF-3246799) was identified as a candidate for clinical development for the treatment of SUI. In addition, it proved to be critical to build an understanding of the translation between recombinant cell-based systems, native tissue preparations and in vivo preclinical models. This was a significant undertaking and proved to be crucial in compound selection.

The scaffold diversity of 7 representative commercial and proprietary compound libraries is explored for the first time using both Murcko frameworks and Scaffold Trees. We show that Level 1 of the Scaffold Tree is useful for the characterization of scaffold diversity in compound libraries and offers advantages over the use of Murcko frameworks. This analysis also demonstrates that the majority of compounds in the libraries we analyzed contain only a small number of well represented scaffolds and that a high percentage of singleton scaffolds represent the remaining compounds. We use Tree Maps to clearly visualize the scaffold space of representative compound libraries, for example, to display highly populated scaffolds and clusters of structurally similar scaffolds. This study further highlights the need for diversification of compound libraries used in hit discovery by focusing library enrichment on the synthesis of compounds with novel or underrepresented scaffolds.

Transforming growth factor-β (TGF-β) signalling plays a key role in colorectal cancer (CRC). Bone morphogenetic protein-4 (BMP4) is a member of the TGF-β family of signal transduction molecules. To examine if germline mutation in BMP4 causes CRC we analysed 504 genetically enriched CRC cases (by virtue of early-onset disease, family history of CRC) for mutations in the coding sequence of BMP4. We identified three pathogenic mutations, p.R286X (g.8330C>T), p.W325C (g.8449G>T) and p.C373S (g.8592G>C), amongst the CRC cases which were not observed in 524 healthy controls. p.R286X localizes to the N-terminal of the TGF-β1 prodomain truncating the protein prior to the active domain. p.W325C and p.C373S mutations are predicted from protein homology modelling with BMP2 to impact deleteriously on BMP4 function. Segregation of p.C373S with adenoma and hyperplastic polyp in first-degree relatives of the case suggests germline mutations may confer a juvenile polyposis-type phenotype. These findings suggest mutation of BMP4is a cause of CRC and the value of protein-based modelling in the elucidation of rare disease-causing variants.

Lead optimization studies using 7 as the starting point led to a new class of imidazo[4,5-b]pyridine-based inhibitors of Aurora kinases that possessed the 1-benzylpiperazinyl motif at the 7-position, and displayed favorable in vitro properties. Cocrystallization of Aurora-A with 40c (CCT137444) provided a clear understanding into the interactions of this novel class of inhibitors with the Aurora kinases. Subsequent physicochemical property refinement by the incorporation of solubilizing groups led to the identification of 3-((4-(6-bromo-2-(4-(4-methylpiperazin-1-yl)phenyl)-3H-imidazo[4,5-b]pyridin-7-yl)piperazin-1-yl)methyl)-5-methylisoxazole (51, CCT137690) which is a potent inhibitor of Aurora kinases (Aurora-A IC(50) = 0.015 +/- 0.003 muM, Aurora-B IC(50) = 0.025 muM, Aurora-C IC(50) = 0.019 muM). Compound 51 is highly orally bioavailable, and in in vivo efficacy studies it inhibited the growth of SW620 colon carcinoma xenografts following oral administration with no observed toxicities as defined by body weight loss.

Aurora kinases are a family of protein kinases that have a key role in multiple stages of mitosis. Over-expression of Aurora kinases, particularly Aurora A, has been demonstrated in a number of solid tumors and hematological malignancies. Not surprisingly, these serine/threonine kinases have become attractive small molecule targets for cancer therapeutics, with several inhibitors currently in early-phase clinical trials. A small number of compounds developed to date are highly selective for either Aurora A or Aurora B, while the majority inhibit both Aurora A and Aurora B; many of these compounds exhibit 'off-target' inhibition of kinases such as ABL, JAK2 and FLT3. It is currently unclear whether the therapeutic activity of these compounds in leukemia is primarily due to selective Aurora or multi-kinase inhibition. The most promising application for Aurora kinase inhibitors to date appears to be in FLT3-mutated acute myeloid leukemia (AML) and imatinib-resistant chronic myeloid leukemia/Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia, particularly when caused by the T315I mutation. Here we review the growing body of evidence supporting the use of Aurora kinase inhibitors as effective agents for AML and Ph+ leukemias. Leukemia (2010) 24, 671-678; doi: 10.1038/leu.2010.15; published online 11 February 2010

The production of selective protein kinase inhibitors is often frustrated by the similarity of the enzyme active sites. For this reason, it is challenging to design inhibitors that discriminate between the three Aurora kinases, which are important targets in cancer drug discovery. We have used a triple-point mutant of Aurora-A (AurA(x3)) which mimics the active site of Aurora-B to investigate the structural basis of MLN8054 selectivity. The bias toward Aurora-A inhibition by MLN8054 is fully recapitulated by AurAx3 in vitro. X-ray crystal structures of the complex suggest that the basis for the discrimination is electrostatic repulsion due to the T217E substitution, which we have confirmed using a single-point mutant. The activation loop of Aurora-A in the AurA(x3)-MLN8054 complex exhibits an unusual conformation in which Asp(274) and Phe(275) side chains point into the interior of the protein. There is to our knowledge no documented precedent for this conformation, which we have termed DFG-up. The sequence requirements of the DFG-up conformation suggest that it might be accessible to only a fraction of kinases. MLN8054 thus circumvents the problem of highly homologous active sites. Binding of MLN8054 to Aurora-A switches the character of a pocket within the active site from polar to a hydrophobic pocket, similar to what is observed in the structure of Aurora-A bound to a compound that induces DFG-out. We propose that targeting this pocket may be a productive route in the design of selective kinase inhibitors and describe the structural basis for the rational design of these compounds.

4-Amino-3,5-dihalopyridines have been efficiently prepared via microwave-assisted nucleophilic aromatic substitution of 3,4,5-trihalopyridines using 1-1.1 equiv of primary and secondary amines. The reaction is also applicable to electron rich arylamines. (C) 2010 Elsevier Ltd. All rights reserved.

Novel approaches for treating chronic pain are required to address a widely recognized, yet largely underserved and unmet, clinical need. The recently discovered link between tetrahydrobiopterin (BH4) synthesis and pain in preclinical models and humans provides a promising new approach for treating neuropathic and other forms of chronic pain. The rate-limiting enzyme in BH4 synthesis, guanosine triphosphate cyclohydrolase 1 (GCH1), and sepiapterin reductase (SPR) are both promising drug targets based on initial active-site characterization of the SARs of these two enzymes. Reducing the elevated BH4 levels associated with pain to baseline, while maintaining sufficient BH4 levels to limit side effects is the goal of discovery programs for novel therapeutics targeting GCH1 or SPR.

The Wnt signaling pathway is frequently deregulated in cancer due to mutations in genes encoding APC, beta-catenin, and axin. To identify small-molecule inhibitors of Wnt signaling as potential therapeutics, a diverse chemical library was screened using a transcription factor reporter cell line in which the activity of the pathway was induced at the level of Disheveled protein. A series of deconvolution studies was used to focus on three compound series that selectively killed cancer cell lines with constitutive Wnt signaling. Activities of the compounds included the ability to induce degradation of beta-catenin that had been stabilized by a glycogen synthase kinase-3 (GSK-3) inhibitor. This screen illustrates a practical approach to identify small-molecule inhibitors of Wnt signaling that can seed the development of agents suitable to treat patients with Wnt-dependent tumors. Cancer Res; 70(14); 5963-73. (C) 2010 AACR.

Co-crystallisation of the imidazo[1,2-a]pyrazine derivative 15 (3-chloro-N-(4-morpholinophenyl)-6-(pyridin-3-yl)imidazo[1,2-a]pyrazin-8-amine) with Aurora-A provided an insight into the interactions of this class of compound with Aurora kinases. This led to the design and synthesis of potent Aurora-A inhibitors demonstrating up to 70-fold selectivity in cell-based Aurora kinase pharmacodynamic biomarker assays.

Cellular stress in early mitosis activates the antephase checkpoint, resulting in the decondensation of chromosomes and delayed mitotic progression. Checkpoint with forkhead-associated and RING domains (CHFR) is central to this checkpoint, and its activity is ablated in many tumors and cancer cell lines through promoter hypermethylation or mutation. The interaction between the PAR-binding zinc finger (PBZ) of CHFR and poly(ADP-ribose) (PAR) is crucial for a functional antephase checkpoint. We determined the crystal structure of the cysteine-rich region of human CHFR (amino acids 425-664) to 1.9 Å resolution, which revealed a multizinc binding domain of elaborate topology within which the PBZ is embedded. The PBZ of CHFR closely resembles the analogous motifs from aprataxin-like factor and CG1218-PA, which lie within unstructured regions of their respective proteins. Based on co-crystal structures of CHFR bound to several different PAR-like ligands (adenosine 5'-diphosphoribose, adenosine monophosphate, and P(1)P(2)-diadenosine 5'-pyrophosphate), we made a model of the CHFR-PAR interaction, which we validated using site-specific mutagenesis and surface plasmon resonance. The PBZ motif of CHFR recognizes two adenine-containing subunits of PAR and the phosphate backbone that connects them. More generally, PBZ motifs may recognize different numbers of PAR subunits as required to carry out their functions.

The relevance of the melanocortin system to sexual activity is well established, and nonselective peptide agonists of the melanocortin receptors have shown evidence of efficacy in human sexual dysfunction. The role of the MC4 receptor subtype has received particular scrutiny, but the sufficiency of its selective activation in potentiating sexual response has remained uncertain owing to conflicting data from studies in preclinical species. We describe here the discovery of a novel series of small-molecule MC4 receptor agonists derived from library hit 2. The addition of methyl substituents at C3 and C5 of the 4-phenylpiperidin-4-ol ring was found to be markedly potency-enhancing, enabling the combination of low nanomolar potencies with full rule-of-five compliance. In general, the series shows only micromolar activity at other melanocortin receptors. Our preferred compound 40a provided significant systemic exposure in humans on both sublingual and oral administration and was safe and well tolerated up to the maximum tested dose. In a pilot clinical study of male erectile dysfunction, the highest dose of 40a tested (200 mg) provided a similar level of efficacy to sildenafil.

This Letter reports the design and synthesis of several novel series of piperazinyl pyrimidinones as 5-HT2C agonists. Several of the compounds presented exhibit good in vitro potency and selectivity over the closely related 5-HT2A and 5-HT2B receptors. Compound 11 was active in in vivo models of stress urinary incontinence. (C) 2009 Elsevier Ltd. All rights reserved.

The genesis of any toxicological or safety outcome is multifactorial and complex; for this reason, it can be difficult for drug discovery projects to factor the avoidance of toxicity outcomes into their target design. A focus on readily measurable parameters from high-throughput in vitro assays (e.g., primary potency, clearance) is easier to handle and have become the mainstays of drug discovery projects. However, the fundamental origins of adverse safety or toxicity findings can be considered as deriving from four parameters, all of which are in the control of the drug designer. These can be described as primary pharmacology, off target pharmacology, the presence of a defined structural fragment that can be associated with adverse outcomes and the overall physicochemical properties of the molecule that may predispose it to adverse outcomes. In the drug discovery community, there has been recognition for many years of the influence of physicochemical drug properties (in particular lipophilicity) on the toxicology profile of compounds, and recent research is now beginning to quantify that risk in a probabilistic sense. This review focuses on the overall properties of classes of molecules that are associated with an increased probability of adverse outcomes in in vivo studies.

The SAR of a series of pyridazinone derived 5-HT(2C) agonists has been explored and resulted in identification of a compound with excellent levels of 5-HT(2C) functional agonism and selectivity over 5-HT(2A) and 5-HT(2B). This compound displayed good in vivo efficacy in pre-clinical models of stress urinary incontinence, despite having physiochemical properties commensurate with impaired CNS penetration.

Relationships between physicochemical drug properties and toxicity were inferred from a data set consisting of animal in vivo toleration (IVT) studies on 245 preclinical Pfizer compounds; an increased likelihood of toxic events was found for less polar, more lipophilic compounds. This trend held across a wide range of types of toxicity and across a broad swath of chemical space. (C) 2008 Elsevier Ltd. All rights reserved.

A novel series of 1-(2-phenoxyphenyl)methanamines is disclosed, which possess selective dual 5-HT and NA reuptake pharmacology. Analogues with good human in vitro metabolic stability, hERG selectivity and passive membrane permeability were identified.

Starting from 2, several highly potent C5a receptor antagonists were synthesised through alpha-amide substitution. Attempts to increase the polarity of these compounds through the introduction of basic centres or incorporation into weakly basic heterocycles is described.

The optimisation of a series of amides for C5a receptor binding and functional activity, and physicochemical properties is described. The initial hit, 1 (IC(50) 1 microM), was discovered during high throughput screening, from which highly potent C5a receptor antagonists (e.g.14, IC(50) 5 nM) were developed.

This paper reports the synthesis and biological activity of a novel series of aryl-morpholine dopamine receptor agonists. Several compounds show high levels of functional selectivity for the D3 over the D2 dopamine receptor. Compound 26 has > 1000-fold functional selectivity and has been successfully progressed in vivo using an intranasal delivery route. (c) 2007 Elsevier Ltd. All rights reserved.

6-Cyclohexyl-N-hydroxy-3-(1,2,4-oxadiazol-5-yl)hexanamides were previously disclosed as inhibitors of procollagen C-proteinase (PCP) culminating in the identification of amide 1. Our objective was to discover a second inhibitor that would have improved affinity for PCP and to optimize properties for transepidermal delivery (TED) to intact skin. Further investigation of this template identified a number of potent PCP inhibitors (IC50 values of 2-6 nM) with improved TED flux. Sulfonamide 56 had excellent PCP enzyme activity when measured with a peptide substrate (Ki 8.7 nM) or with the endogenous substrate procollagen (IC50 3.4 nM) and demonstrates excellent selectivity over MMPs involved in wound healing (>10 000-fold). In the fibroplasia model, 56 inhibited deposition of insoluble collagen by 76 +/- 2% at 10 microM and was very effective at penetrating human skin in vitro with a TED flux of 1.5 microg/cm2/h, which compares favorably with values for agents that are known to penetrate skin well in vivo. Based on this profile, 56 (UK-421,045) was selected as a candidate for further preclinical evaluation as a topically applied, dermal anti-scarring agent.

Dysfunction of female sexual desire, arousal, or orgasm affects approximately 30% of women. Early attempts to treat female sexual dysfunction arose out of programs developed for male erectile dysfunction and have proven largely unsuccessful. A new wave of targets is now being pursued; many of these targets are postulated to modulate central pathways. Classical neurotransmitter systems, such as dopamine and serotonin, as well as the neuropeptide melanocortin, are receiving the most attention. Early clinical data look promising; however, clinical trial methodology in female sexual dysfunction is not well developed and only further testing will determine whether these treatments meet regulatory hurdles and satisfy patient need.

Thrombin-activatable fibrinolysis inhibitor (TAFI) has emerged as a key link between the coagulation and fibrinolysis cascades and represents a promising new target for the treatment of thrombosis. A novel series of imidazolepropionic acids has been designed that exhibit high potency against activated TAFI (TAFIa) and excellent selectivity over plasma carboxypeptidase N (CPN). Structure activity relationships suggest that the imidazole moiety plays a key role in binding to the catalytic zinc of TAFIa, and this has been supported by crystallographic studies using porcine pancreatic carboxypeptidase B as a surrogate for TAFIa. The SAR program led to the identification of 21 (TAFIa Ki = 10 nM, selectivity TAFIa/CPN > 1000) as a candidate for clinical development. Compound 21 exhibited antithrombotic efficacy in a rabbit model of venous thrombosis, yet had no effect on surgical bleeding in the rabbit. In addition, 21 exhibited an excellent preclinical and clinical pharmacokinetic profile, characterized by paracellular absorption, low clearance, and a low volume of distribution, fully consistent with its physicochemical properties of low molecular weight (MW = 239) and high hydrophilicity (log D = -2.8). These data indicate 21 (UK-396,082) has potential as a novel TAFIa inhibitor for the treatment of thrombosis and other fibrin-dependent diseases in humans.

Furosemide, a loop diuretic, causes hepatic necrosis in mice. Previous evidence suggested hepatotoxicity arises from metabolic bioactivation to a chemically reactive metabolite that binds to hepatic proteins. To define the nature of the toxic metabolite, we examined the relationship between furosemide metabolism in CD-1 mice and Wistar rats. Furosemide (1.21 mmol/kg) was shown to cause toxicity in mice, but not rats, at 24 h, without resulting in glutathione depletion. In vivo covalent binding to hepatic protein was 6- fold higher in the mouse (1.57 +/- 0.98 nmol equivalent bound/mg protein) than rat (0.26 +/- 0.13 nmol equivalent bound/mg protein). In vivo covalent binding to mouse hepatic protein was reduced 14- fold by a predose of the cytochrome P450 (P450) inhibitor, 1-aminobenzotriazole (ABT; 0.11 +/- 0.04 nmol equivalent bound/ mg protein), which also reduced hepatotoxicity. Administration of [14C] furosemide to bile duct-cannulated rats demonstrated turnover to glutathione conjugate (8.8 +/- 2.8%), gamma-ketocarboxylic acid metabolite ( 22.1 +/- 3.3%), N-dealkylated metabolite (21.1 +/- 2.9%), and furosemide glucuronide (12.8 +/- 1.8%). Furosemide-glutathione conjugate was not observed in bile from mice dosed with [C-14] furosemide. The novel gamma-ketocarboxylic acid, identified by nuclear magnetic resonance spectroscopy, indicates bioactivation of the furan ring. Formation of gamma-ketocarboxylic acid was P450-dependent. In mouse liver microsomes, a gamma-ketoenal furosemide metabolite was trapped, forming an N-acetylcysteine/N-acetyl lysine furosemide adduct. Furosemide (1 mM, 6 h) became irreversibly bound to primary mouse and rat hepatocytes, 0.73 +/- 0.1 and 2.44 +/- 0.3 nmol equivalent bound/ mg protein, respectively, which was significantly reduced in the presence of ABT, 0.11 +/- 0.03 and 0.21 +/- 0.1 nmol equivalent bound/ mg protein, respectively. Furan rings are part of new chemical entities, and mechanisms underlying species differences in toxicity are important to understand to decrease the drug attrition rate.

Through the use of computational modeling, a series of pyrimidinetrione-based inhibitors of MMP-13 was designed based on a lead inhibitor identified through file screening. Incorporation of a biaryl ether moiety at the C-5 position of the pyrimidinetrione ring resulted in a dramatic enhancement of MMP-13 potency. Protein crystallography revealed that this moiety binds in the S(1)(') pocket of the enzyme. Optimization of the C-4 substituent of the terminal aromatic ring led to incorporation of selectivity versus MMP-14 (MT-1 MMP). Structure activity relationships of the biaryl ether substituent are presented as is pharmacokinetic data for a compound that meets our in vitro potency and selectivity goals.

1,1'-Binaphthyl and 1,1'-dinaphthyl ether systems have been prepared via double benzyne-furan cycloadditions, and a dibenzofuran derivative was formed as a major product in the lithiation of two di-(chloroaryl) ethers. (C) 2004 Published by Elsevier Ltd.

The design, synthesis and biological properties of homochiral non-steroidal inhibitors of both isozymes of human 5 alpha-reductase are described. The o-hydroxy aniline moiety of the initial lead (1) can be replaced by a 3-acyl indole isostere, whilst the minimum energy conformation of the benzyl ether in the potent inhibitor (3) is mimicked by the conformationally locked benzodioxolane system in the potent non-steroidal inhibitor (7). Pharmacokinetics and oral efficacy in a rat model of BPH are presented for (3) and (7). Copyright (C) 1996 Elsevier Science Ltd

Zirconocene eta(2)-imine complexes formed by a C-H activation route from a variety of amines are trapped by omega-halo-alkenes or -alkynes to afford 2,3-disubstituited pyrrolidines, piperidines and perhydroazepines on work up and cyclisation. In some cases ii was necessary to use a protected hydroxyl group rather than the halide and cyclise in a separate step through selective formation of the O-mesylate.

Sequential addition of a magnesium amide and methyl magnesium chloride to zirconocene dichloride provides a practical synthesis of zirconocene methyl amides. Thermolysis of these zirconocene complexes in the presence of unactivated alkenes and alkynes gives, on protonolysis, alpha-alkylated or alpha-vinylated amines.

The formation of eta2-imine-zirconocene complexes (zirconaziridines) (CP2Zr(NR1CR2R3) by elimination of R4H from CP2Zr(R4)(NR1CHR2R3) has been investigated with regard to the variation in R1, R2, R3, and R4, in particular by making use of Hammett type structure/rate correlations (R1, R2, R4 = p-XC6H4, X = Me2N, MeO, H, Cl, CO2Me; R1, rho = 3.2; R2, rho = 0.5; R4, rho = -1.6). The elimination is first order in the zirconocene complex, has a deuterium isotope effect for the hydrogen eliminated of 8.2 at 20-degrees-C, and kinetic studies on Cp2Zr(Me)(NPhCHMe2) give the activation parameters DELTAH(double dagger) = 100 kJ mol-1 and DELTAS(double dagger) = -19 J K-1 mol-1 for the elimination of methane. A cyclometalation involving deprotonation alpha to nitrogen by (R4)- best fits the data. The relationship between the rate of the reaction and the structure of the amine shows a marked dependency on both electronic and steric effects ranging between no reaction after 48 h at 110-degrees-C for piperidine to below room temperature for silylamines and benzylanilines. For the first time.eta2-imine complexes have been formed even from simple amines such as dibutylamine and trapped with an alkyne to form secondary allylic amines on workup. In the absence of a trap eta2-(PhN=CMe2)ZrCP2 rearranges via a rapidly reversible hydride shift to afford a eta3-azaallyl-zirconocene hydride.

Beta-hydrogen activation via loss of methane from 6-(zirconocene(methyl))-3,4-dihydro-2H-pyran affords eta2-(3-oxacyclohexyne)-zirconocene which inserts unactivated alkenes and alkynes to afford elaborated dihydropyrans on aqueous work-up.

An improved method for the N-formylation of secondary amines using chlorotrimethylsilane and imidazole in NN-dimethylformamide is described. The reaction conditions are tolerant of ester functional groups, and an amine hydrochloride may be N-formylated using a slight modification of the procedure.

Eta(2)-Ketimine complexes of zirconocene can be generated by a C-H activation process from alpha,alpha-disubstituted amines and react with a variety of unsaturated substrates to afford alpha-trisubstituted amines.