11-Step and Scalable Total Synthesis of Hamigeran M Enabled by Five C-H Functionalizations.

We report the convergent total synthesis of (±)-hamigeran M, enabled by five C-H functionalization reactions and proceeding in 11 steps in 3.9% overall yield. The C-H functionalizations include a hydroxy-directed C-H borylation, one C-H metalation-1,2-addition, one C-H metalation-Negishi coupling, a late-stage oxazole-directed C-H borylation-oxidation, and one electrophilic bromination. Two of these five C-H functionalizations forged strategic C-C bonds in the seven-membered ring of hamigeran M. The oxazole-directed C-H borylation-oxidation was unprecedented and ensured a late-stage hydroxylation. Other key steps include a tandem Suzuki reaction-lactonization to join the cyclopentane building block with the aromatic moiety and a hydrogen-atom transfer reaction to reduce a challenging tetrasubstituted double bond.

Recent advances in total syntheses of natural products containing the benzocycloheptane motif.

Covering: 2010 to 2020Benzocycloheptane is a fundamental and unique structural motif found in pharmaceuticals and natural products. The total syntheses of natural products bearing the benzocycloheptane subunit are challenging and there are only a few efficient approaches to access benzocycloheptane. Thus, new methods and innovative strategies for preparing such natural products need to be developed. In this review, recent progress in the total syntheses of natural products bearing the benzocycloheptane motif is presented, and key transformations for the construction of benzocycloheptane are highlighted. This review provides a useful guide for those engaged in the syntheses of natural products containing the benzocycloheptane motif.

Two-Carbon Ring Expansion of 1-Indanones via Insertion of Ethylene into Carbon-Carbon Bonds.

A rhodium-catalyzed direct insertion of ethylene into a relatively unstrained carbon-carbon bond in 1-indanones is reported, which provides a two-carbon ring expansion strategy for preparing seven-membered cyclic ketones. As many 1-indanones are commercially available and ethylene is inexpensive, this strategy simplifies synthesis of benzocycloheptenones that are valuable synthetic intermediates for bioactive compounds but challenging to prepare otherwise. In addition, the reaction is byproduct-free, redox neutral, and tolerant of a wide range of functional groups, which may have implications on unconventional strategic bond disconnections for preparing complex cyclic molecules.

Exploring S1 plasticity and probing S1' subsite of mammalian aminopeptidase N/CD13 with highly potent and selective aminobenzosuberone inhibitors.

In order to probe the S1 and S1' mammalian aminopeptidase N subsites, racemic 1- or 4-substituted 7-aminobenzocyclohepten-6-one derivatives were synthesized and evaluated for their ability to inhibit mammalian aminopeptidase N. We focused on improving the physicochemical and ADME properties of this series by targeting lipophilicity and LELP score. Some 4-heteroaryl substituted analogues displayed reduced lipophilicity and enhanced inhibition potency with Ki values in the nanomolar range.

Synthesis, GluN2B affinity and selectivity of benzo[7]annulen-7-amines.

Due to their beneficial side effect profile, NMDA receptor antagonists interacting selectively with the allosteric ifenprodil binding site of the GluN2B subunit are of major interest for the treatment of neurological and neurodegenerative disorders. A series of benzo[7]annulen-7-amines 6 was designed by conformational restriction of ifenprodil (1). At first the benzo[7]annulen-7-one 11 was prepared in a three-step synthesis comprising of a double Knoevenagel condensation of phthalaldehyde (7) with dimethyl 3-oxoglutarate (8), hydrogenation of 9 and saponification/decarboxylation of 10. Reductive amination of the ketone 11 with primary amines and NaBH(OAc)3 led to the secondary amines 6a-d, cis-6h and trans-6i. The tertiary amines 6e-g were obtained by SN2-substitution of the nosylate 13. Although H-bond forming substituents in 2- and 5-position are missing, the amines 6 exhibit high affinity towards GluN2B containing NMDA receptors. A distance of four to five bond lengths between the basic amino moiety and the phenyl ring in the side chain appears to be optimal for high GluN2B affinity. The phenylcyclohexylamine cis-6h and the 4-benzylpiperidine 6g show the highest GluN2B affinities (Ki=2.3nM and 2.9nM, respectively). With respect to selectivity against the PCP binding site, σ1 and σ2 receptors the phenylpiperazine 6f is the most promising GluN2B antagonist.

Synthesis and evaluation as potential anticancer agents of novel tetracyclic indenoquinoline derivatives.

We report the synthesis and evaluation as potential anticancer agents of a series of tetracyclic indenoquinolines. The compounds, which are obtained through the photoisomerization of Diels-Alder adducts formed between purpurogallin derivatives and nitrosobenzene, have in vitro antiproliferative activities in the µM to nM range against breast (MCF-7), lung epithelial (A-549), and cervical (HeLa) adenocarcinoma cells. The cytotoxicities of several of the novel tetracycles are comparable to or better than that of camptothecin. A strong correlation between the activity of the compounds and their aromaticity and planarity was observed, suggesting a mode of action similar to that of topoisomerase poisons.

Synthesis of amino-hydroxy-benzocycloheptenones as potent, selective, non-peptidic dinuclear zinc metalloaminopeptidase inhibitors.

Racemic trisubstituted benzocycloheptanes were synthesized and evaluated for their ability to inhibit metalloaminopeptidase activities. A highly selective nanomolar inhibitor of a prototypical 'two zinc' aminopeptidase from the M28 family was observed with these tridentate species, while bidentate analogs proved to be highly selective for the 'one zinc' M1 family of enzymes. The selectivity profile of these new, low molecular weight structures may guide the design of specific, non-peptidic inhibitors of binuclear aminopeptidases.

Synthesis of structurally diverse benzosuberene analogues and their biological evaluation as anti-cancer agents.

Diversely functionalized, fused aryl-alkyl ring systems hold a prominent position as well-established molecular frameworks for a variety of anti-cancer agents. The benzosuberene (6,7 fused, also referred to as dihydro-5H-benzo[7]annulene and benzocycloheptene) ring system has emerged as a valuable molecular core component for the development of inhibitors of tubulin assembly, which function as antiproliferative anti-cancer agents and, in certain cases, as vascular disrupting agents (VDAs). Both a phenolic-based analogue (known as KGP18, compound 39) and its corresponding amine-based congener (referred to as KGP156, compound 45), which demonstrate strong inhibition of tubulin assembly (low micromolar range) and potent cytotoxicity (picomolar range for KGP18 and nanomolar range for KGP156) are noteworthy examples of such benzosuberene-based compounds. In order to extend the structure-activity relationship (SAR) knowledge base related to benzosuberene anti-cancer agents, a series of eleven analogues (including KGP18) were prepared in which the methoxylation pattern on the pendant aryl ring as well as functional group incorporation on the fused aryl ring were varied. The synthetic approach to these compounds featured a sequential Wittig olefination, reduction, Eaton's reagent-mediated cyclization strategy to achieve the core benzosuberone intermediate, and represented a higher-yielding synthesis of KGP18 (which we prepared previously through a ring-expansion strategy). Incorporation of a fluorine or chlorine atom at the 1-position of the fused aryl ring or replacement of one of the methoxy groups with hydrogen (on the pendant aryl ring of KGP18) led to benzosuberene analogues that were both strongly inhibitory against tubulin assembly (IC50 approximately 1.0 µM) and strongly cytotoxic against selected human cancer cell lines (for example, GI50=5.47 nM against NCI-H460 cells with fluoro-benzosuberene analogue 37). A water-soluble phosphate prodrug salt of KGP18 (referred to as KGP265, compound 44) and a water-soluble serinamide salt (compound 48) of KGP156 were also synthesized and evaluated in this study.

Novel radioiodinated {gamma}-hydroxybutyric acid analogues for radiolabeling and Photolinking of high-affinity {gamma}-hydroxybutyric acid binding sites.

γ-Hydroxybutyric acid (GHB) is a therapeutic drug, a drug of abuse, and an endogenous substance that binds to low- and high-affinity sites in the mammalian brain. To target the specific GHB binding sites, we have developed a (125)I-labeled GHB analog and characterized its binding in rat brain homogenate and slices. Our data show that [(125)I]4-hydroxy-4-[4-(2-iodobenzyloxy)phenyl]butanoate ([(125)I]BnOPh-GHB) binds to one site in rat brain cortical membranes with low nanomolar affinity (K(d), 7 nM; B(max), 61 pmol/mg protein). The binding is inhibited by GHB and selected analogs, but not by γ-aminobutyric acid. Autoradiography using horizontal slices from rat brain demonstrates the highest density of binding in hippocampus and cortical regions and the lowest density in the cerebellum. Altogether, the findings correlate with the labeling and brain regional distribution of high-affinity GHB sites or [(3)H](E,RS)-(6,7,8,9-tetrahydro-5-hydroxy-5H-benzocyclohept-6-ylidene)acetic acid ([(3)H]NCS-382) binding sites. Using a (125)I-labeled photoaffinity derivative of the new GHB ligand, we have performed denaturing protein electrophoresis and detected one major protein band with an apparent mass of 50 kDa from cortical and hippocampal membranes. [(125)I]BnOPh-GHB is the first reported (125)I-labeled GHB radioligand and is a useful tool for in vitro studies of the specific high-affinity GHB binding sites. The related photoaffinity linker [(125)I]4-hydroxy-4-[4-(2-azido-5-iodobenzyloxy)phenyl]butanoate can be used as a probe for isolation of the elusive GHB binding protein.

Synthesis and evaluation of novel tricyclic benzo[4.5]cyclohepta[1.2]pyridine derivatives as NMDA/NR2B antagonists.

A novel series of annulated tricyclic compounds was synthesized and evaluated as NMDA/NR2B antagonists. Structure-activity development was directed towards in vitro optimization of NR2B activity and selectivity over the hERG K(+) channel. Preferred compounds were subsequently evaluated for selectivity in an alpha(1)-adrenergic receptor binding counter-screen and a cell-based assay of NR2B activity.

A Computer - Aided Drug Designing for Pharmacological Inhibition of Mutant ALK for the Treatment of Non-small Cell Lung Cancer.

BACKGROUND: Lung cancer is the most common among all the types of cancer worldwide with 1.8 million people diagnosed every year, leading to 1.6 million deaths every year according to the American cancer society. The involvement of mutated Anaplasic Lymphoma Kinase (ALK) positive fusion protein in the progression of NSCLC has made a propitious target to inhibit and treat NSCLC. In the present study, the main motif is to screen the most effective inhibitor against ALK protein with the potential pharmacological profile. The ligands selected were docked with Molegro Virtual Docker (MVD) and CEP-37440 (PubChem CID- 71721648) was the best docked pre-established compound with a permissible pharmacological profile. METHODS: The selected ligands were docked with Molegro Virtual Docker (MVD). With reference to the obtained compound with the lowest re-rank score, PubChem database was virtually screened to retrieve a large set of similar compounds which were docked to find the compound with higher affinity. Further comparative studies and in silico prediction included pharmacophore studies, proximity energy parameters, ADMET and BOILED-egg plot analysis. RESULTS: CEP-37440 (PubChem CID- 71721648) was the best docked pre-established compound with preferable pharmacological profile and PubChem compound CID-123449015 came out as the most efficient virtually screened inhibitor. Interestingly, the contours of the virtual screened compound PubChem CID- 123449015 fall within our desired high volume cavity of protein having admirable property to control the ALK regulation to prevent carcinogenesis in NSCLC. BOILED-Egg plot analysis depicts that both the compounds have analogous characteristics in the divergent aspects. Moreover, in the evaluations of Blood Brain Barrier, Human Intestinal Absorption, AMES toxicity, and LD50, the virtually screened compound (PubChem CID-123449015) was found within high optimization. CONCLUSION: These investigations denote that the virtually screened compound (PubChem CID- 123449015) is more efficient to be a better prospective candidate for NSCLC treatment having good pharmacological profile than the pre-established compound CEP-37440 (PubChem CID- 71721648) with low re-rank score. The identified virtually screened compound has high potential to act as an ALK inhibitor and can show promising results in the research of non-small cell lung cancer (NSCLC).

Design, synthesis and biological evaluation of dihydronaphthalene and benzosuberene analogs of the combretastatins as inhibitors of tubulin polymerization in cancer chemotherapy.

A novel series of dihydronaphthalene and benzosuberene analogs bearing structural similarity to the combretastatins in terms of 1,2-diarylethene, trimethoxyphenyl, and biaryl functionality has been synthesized. The compounds have been evaluated in regard to their ability to inhibit tubulin assembly and for their cytotoxicity against selected human cancer cell lines. From this series of compounds, benzosuberene analogs 2 and 4 inhibited tubulin assembly at concentrations comparable to that of combretastatin A-4 (CA4) and combretastatin A-1 (CA1). Furthermore, analog 4 demonstrated remarkable cytotoxicity against the three human cancer cell lines evaluated (for example GI(50)=0.0000032 microM against DU-145 prostate carcinoma).

Design, Synthesis, Pharmacological Evaluation and Docking Studies of GluN2B-Selective NMDA Receptor Antagonists with a Benzo[7]annulen-7-amine Scaffold.

Antagonists that selectively target GluN2B-subunit-containing N-methyl-d-aspartate (NMDA) receptors are of major interest for the treatment of various neurological disorders. In this study, relationships between variously substituted benzo[7]annulen-7-amines and their GluN2B affinity were investigated. 2-Nitro-5,6,8,9-tetrahydrobenzo[7]annulen-7-one (8) represents the central building block for the introduction of various substituents at the 2-position and various 7-amino moieties. N-(3-Phenylpropyl)-6,7,8,9-tetrahydro-5H-benzo[7]annulen-7-amines with a 2-NO2 (7 c), 2-Cl (15 c), or 2-OBn group (22 c) show very high GluN2B affinity (Ki =1.6-3.6 nm). Docking studies revealed the same binding poses for benzo[7]annulen-7-amines and ifenprodil at the interface of GluN1b and GluN2B subunits. The large 2-OBn moiety of 22 c occupies a previously unrecognized subpocket, which explains its high GluN2B affinity (Ki =3.6 nm). In two-electrode voltage clamp experiments and cytoprotection assays, the high-affinity GluN2B ligands 7 c, 15 c, and 22 c could not inhibit the glutamate-/glycine-evoked current and cytotoxic effects. However, the analogous phenols 16 c ((3-phenylpropyl)amino moiety) and 16 d ((4-phenylbutyl)amino moiety) with 10-fold lower GluN2B affinity (Ki =28 and 21 nm, respectively) showed promising inhibition of glutamate-/glycine-evoked effects in both assays. The presence of a phenolic hydroxy group seems to be essential for inducing conformational changes of the receptor protein, which finally results in closure of the ion conduction pathway.

Stereochemical considerations and the antiinflammatory activity of 6-amino-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ols and related derivatives.

The antiinflammatory activity of a series of 6-amino-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ols and related derivatives was examined using the reverse passive Arthus reaction (RPAR). The antiinflammatory activity of these compounds was markedly influenced by the stereochemistry of the amino alcohol moiety. The threo diastereomer exhibited activity in the RPAR, while the erythro diastereomer was devoid of any significant antiinflammatory activity. The antiinflammatory activity of the amino alcohols was also significantly influenced by the position and nature of the aromatic substituent. Latentiation of the amino alcohol function resulted in analogues exhibiting antiinflammatory activity equivalent to their amino alcohol precursors. Masking the amino alcohol function as a more stable derivative led to analogues exhibiting an antiinflammatory profile unique to their structural class.

Topography and conformational preferences of 6,7,8,9-tetrahydro-1-hydroxy-N,N-dipropyl-5H-benzocyclohepten-6- ylamin e. A rationale for the dopaminergic inactivity.

In an attempt to rationalize the inability of phenolic benzocycloheptenylamines to activate dopamine (DA) D2 receptors, we have studied the conformational preferences and topography of 6,7,8,9-tetrahydro-1-hydroxy-N,N-dipropyl-5H-benzocyclohepten-6-++ +ylamine (1). Preferred conformations of 1 have been defined by use of experimental (NMR spectroscopic studies) and theoretical (MMP2, AM1, and MNDO calculations) methods. Topographical characteristics were studied by use of molecular graphics. Results from the MMP2 calculations agree with those from the AM1 calculations and the NMR spectroscopic study--1 seems to preferentially adopt chair conformations with a pseudoequatorial C6 substituent. The MNDO calculations, however, produced results that deviate considerably from those of the other theoretical methods. Most likely, pharmacophore conformations of (S)-1 do not present volumes that are part of the DA D2 receptor essential volume. Therefore, it appears that the energy penalty paid by the pharmacophore conformations is responsible for the dopaminergic inactivity of (S)-1. The inactivity of (R)-1 may be due to high energies of pharmacophore conformations and/or to steric factors since these conformations produce large excess volumes that may be part of the DA D2 receptor essential volume. The model used in the present report--a flexible pharmacophore combined with a partial receptor-excluded volume--might be used in the design of new DA D2 receptor agonists.

Catechol derivatives of 6-aminobenzocycloheptene: assessment of dopaminergic effects.

The title compounds were prepared as congeners of the dopaminergically potent 2-amino-5,6-dihydroxytetralin series ("A-5,6-DTN"). None of the variously nitrogen-substituted benzocycloheptenes demonstrated any dopamine-like effects in a variety of assays. The primary amine had alpha 1-adrenoceptor stimulant effects. This lack of dopaminergic effect parallels the inactivity found in 6-aminobenzocycloheptenes bearing no oxygen substitutents, those bearing a single phenolic group, and those bearing a resorcinol 1,3-diphenolic substitution pattern.

Comparison of biological effects of N-alkylated congeners of beta-phenethylamine derived from 2-aminotetralin, 2-aminoindan, and 6-aminobenzocycloheptene.

Three series of bicyclic, semirigid congeners of beta-phenethylamine have been prepared for evaluation of the effect of ring size (and of concomitant conformational variation) on biological activity in a variety of assays for adrenergic and dopaminergic actions. Pharmacologic activity was associated with 2-aminotetralin and 2-aminoindan derivateves, but was not found with 6-aminobenzocycloheptene derivatives. Noteworthy is the ability of several aminotetralins and aminoindans to increase the hot-plate reaction time without eliciting dopaminergic effects. This action was not blocked by pretreatment with naloxone.

Nonisomerizable analogues of (Z)- and (E)-4-hydroxytamoxifen. Synthesis and endocrinological properties of substituted diphenylbenzocycloheptenes.

Substituted 8,9-diphenyl-6,7-dihydro-5H-benzocycloheptenes 6-8, which are ring-fused analogues of (Z)-trans-4-hydroxytamoxifen, (E)-cis-tamoxifen, and (E)-cis-4-hydroxytamoxifen, were synthesized from 7-methoxy-1-benzosuberone. The hydroxy compounds 6 and 8 were individually prepared via a common synthetic intermediate from which either the perfluoro-p-tolyl or the methyl ether functions could be cleaved specifically. Compounds were assayed for binding affinity to estrogen receptors in cytosol and in MCF-7 whole cells and for growth inhibition of MCF-7 cells in vitro and rat uteri in vivo. The endocrinological properties of the cyclic analogues 5-7 paralleled those of the corresponding derivatives of tamoxifen although in the MCF-7 assay 6 was slightly less effective than 4-hydroxytamoxifen at 10(-6) and 10(-7) M. The compound 8 analogues to cis-4-hydroxytamoxifen antagonized the growth stimulation by estradiol of MCF-7 cell or rat uterus growth, and it is therefore an antiestrogen, but its potency was somewhat less, both as an antiestrogen and an estrogen, than reported for cis-4-hydroxytamoxifen attributable to modification of the biochemical properties of the latter by isomerization to the more potent trans isomer. Curiously, in the absence of estradiol, compound 8 stimulated MCF-7 cell growth at low concentration (10(-8) M) but inhibited growth at higher concentration. In contrast, compound 7, which lacked the hydroxy function, was a full estrogen in the rat uterine growth assay. These compounds should be ideal for further structure-activity studies of triarylethylene-based antiestrogens without complications caused by isomerization.

(R)- and (S)-5,6,7,8-tetrahydro-1-hydroxy-N,N-dipropyl-9H-benzocyclohepten- 8-ylamine. Stereoselective interactions with 5-HT1A receptors in the brain.

The enantiomers of 5,6,7,8-tetrahydro-1-hydroxy-N,N-dipropyl-9H-benzocyclohepten-8-++ +ylamine (3) have been synthesized and evaluated for central 5-hydroxytryptamine (5-HT) and dopamine (DA) receptor activity by use of behavioral and biochemical tests in rats. In addition, the ability of the compounds to displace [3H]-8-OH-DPAT from 5-HT1A binding sites was evaluated. The absolute configuration of the enantiomers of 3 was determined indirectly by X-ray diffraction of (+)-(8R,alpha R)-5,6,7,8-tetrahydro-1-methoxy-N-(alpha-phenethyl)-9H- benzocyclohepten-8-ylamine hydrochloride (9.HCl), a resolved synthetic precursor. The stereoselectivity of the interaction of 3 with 5-HT1A receptors was more pronounced than that of 8-hydroxy-2-(dipropylamino)tetralin (1; 8-OH-DPAT); only (R)-3 displayed 5-HT activity. However, (R)-3 was of lower potency than any of the enantiomers of 1. The enantiomer (S)-3, which was found to be inactive as a 5-HT-receptor agonist, appeared to be a weakly potent DA-receptor agonist whereas (R)-3 seemed to be devoid of dopaminergic activity. The conformational preferences of 3 were studied by use of NMR spectroscopy and molecular mechanics calculations. Preferred conformations of (R)-3 are similar in shape to those of the stereoselective 5-HT1A-receptor agonist (2R,3S)-8-hydroxy-3-methyl-2-(dipropylamino)tetralin.

[(3-Pyridylalkyl)piperidylidene]benzocycloheptapyridine derivatives as dual antagonists of PAF and histamine.

A series of [(3-pyridylalkyl)piperidylidene]- and (nicotinoylpiperidylidene)benzocycloheptapyridine derivatives, Ia,b, were prepared and evaluated for PAF antagonist and H1 antihistamine activity. PAF antagonist activity was investigated by the in vitro PAF-induced platelet aggregation assay (PPA) and the in vivo PAF-induced hypotension test in rats (PH) and mortality test in mice (PM). For the evaluation of H1 antihistamine activity, the in vitro histamine-induced contraction of the guinea-pig ileum assay (HC) and the in vivo histamine-induced hypotension test (HH) in normotensive rats were used. The potential antiallergic activity of the compounds was evaluated using the active anaphylactic shock test in mice. These compounds are structurally related to loratadine (1) and were generated by replacement of the ethoxycarbonyl group of 1 with substituted 3-pyridylmethyl and nicotinoyl moieties. Both anti-PAF and H1 antihistamine activities have shown a high dependence on the exact nature and position of the substituent in the pyridine ring. Optimum structure 19 (UR-12592) incorporating a (5-methyl-3-pyridyl)methyl radical displayed an unique dual activity inhibiting both PAF-induced effects (PPA, IC50 = 3.7 microM; PH, ID50 = 0.44 mg/kg iv; PM, ID50 = 1.9 mg/kg po) and histamine-induced effects (HC, IC50 = 3.9 nM; HH, ID50 = 1.4 mg/kg iv). Furthermore, 19 was highly active in the passive cutaneous anaphylactic shock in rats (ID50 = 1.2 mg/kg po) and strongly protected mice and rats from mortality induced by endotoxin (ID50 = 1.2 and 0.5 mg/kg iv, respectively). Compound 19 showed itself to be devoid of CNS depressant effects, neither modifying spontaneous motor activity nor prolonging barbiturate-sleeping time in mice at a dose of 100 mg/kg po, and is now under development.