Isoquinoline Moiety Research Articles

Crystal structures of human cholinesterases in complex with huprine W and tacrine: elements of specificity for anti-Alzheimer's drugs targeting acetyl- and butyryl-cholinesterase

The multifunctional nature of Alzheimer's disease calls for MTDLs (multitarget-directed ligands) to act on different components of the pathology, like the cholinergic dysfunction and amyloid aggregation. Such MTDLs are usually on the basis of cholinesterase inhibitors (e.g. tacrine or huprine) coupled with another active molecule aimed at a different target. To aid in the design of these MTDLs, we report the crystal structures of hAChE (human acetylcholinesterase) in complex with FAS-2 (fasciculin 2) and a hydroxylated derivative of huprine (huprine W), and of hBChE (human butyrylcholinesterase) in complex with tacrine. Huprine W in hAChE and tacrine in hBChE reside in strikingly similar positions highlighting the conservation of key interactions, namely, π-π/cation-π interactions with Trp86 (Trp82), and hydrogen bonding with the main chain carbonyl of the catalytic histidine residue. Huprine W forms additional interactions with hAChE, which explains its superior affinity: the isoquinoline moiety is associated with a group of aromatic residues (Tyr337, Phe338 and Phe295 not present in hBChE) in addition to Trp86; the hydroxyl group is hydrogen bonded to both the catalytic serine residue and residues in the oxyanion hole; and the chlorine substituent is nested in a hydrophobic pocket interacting strongly with Trp439. There is no pocket in hBChE that is able to accommodate the chlorine substituent.

Borylated Arylisoquinolines: Photophysical Properties and Switching Behavior of Promising Tunable Fluorophores

A series of nine borylated arylisoquinolines has been prepared with systematic variation in their electronic properties and their photophysical properties were investigated. The color of their fluorescence can be finely tuned by changing the properties of the aryl moiety, which is involved in internal-charge-transfer processes. For example, methoxy-substituted compound 5 showed an intense green emission, whereas dimethylamino-substituted compound 6 showed an orange-red emission. These new fluorophores were tested for their potential as molecular switches with external ionic stimuli, such as protons and fluoride ions. On the one hand, protonation of the isoquinoline moiety led to fluorescence enhancement for compounds that showed weak charge transfer and fluorescence quenching for compounds that showed strong charge transfer. On the other hand, the formation of ate complexes with fluoride led to strong fluorescence quenching in all of the investigated cases.

Quinoline-based fluorescent zinc sensors with enhanced fluorescence intensity, Zn/Cd selectivity and metal binding affinity by conformational restriction

Two cyclohexanediamine-based tetrakisquinoline derivatives, N,N,N',N'-tetrakis(2-quinolylmethyl)-trans-1,2-cyclohexanediamine (TQDACH) and N,N,N',N'-tetrakis(1-isoquinolylmethyl)-trans-1,2-cyclohexanediamine (1-isoTQDACH), have been prepared and their zinc-induced fluorescent response was investigated. In DMF-H2O (1 : 1) solution, TQDACH exhibits increase of fluorescence at 455 nm in the presence of 1 eq. of zinc ion (λ(ex) = 317 nm, φ = 0.010). Similarly, 1-isoTQDACH exhibited fluorescence enhancement upon binding with zinc (λ(ex) = 325 nm, λ(em) = 352 and 475 nm, φ = 0.032). The fluorescence intensity ratio induced by cadmium relative to zinc (I(Cd)/I(Zn)) for these 1,2-cyclohexanediamine probes is lower than those for the corresponding ethylenediamine derivatives, TQEN and 1-isoTQEN. Crystal structures of the zinc and cadmium complexes of TQDACH and 1-isoTQDACH reveal the superior metal binding ability of the 1,2-cyclohexanediamine and isoquinoline moieties in comparison to ethylenediamine and quinoline. The conformational restriction afforded by the 1,2-cyclohexanediamine skeleton upon zinc binding leads to enhanced fluorescence intensity and strong metal binding affinity.

Creation of readily accessible and orally active analogue of cortistatin a.

Syntheses of structurally simplified analogues of cortistatin A (1), a novel antiangiogenic steroidal alkaloid from Indonesian marine sponge, and their biological activities were investigated. The analogues were designed by considering the 3-D structure of 1. Compound 30, in which the isoquinoline moiety was appended to the planar tetracyclic core structure, showed potent antiproliferative activity against human umbilical vein endothelial cells (HUVECs) together with high selectivity and also showed in vivo antiangiogenic activity and significant antitumor effect by oral administration.

Synthesis of New Derivatives of Heterocyclic Compounds Containing Pyridine, Pyrimidine and Triazole Ortho-Fused to Isoquinoline Moiety

4-Amino-9,10-dimethoxy-2-phenyl-6,7-dihydro-2(H)-pyrido[2,1-a]isoquinoline-1,3-dicarbonitrile derivatives 4a-c were obtained from the reaction of 6,7-dimethoxy-3,4-dihydroisoqinoline-1-acetonitrile 1 with arylidenemalononitrile 2a-c in boiling acetonitile in the presence of piperidine. The reaction of 4a-c with triethyl orthoformate in acetic anhydride at reflux give the ethoxymethyleneamino derivatives 5a-c. Compounds 5a-c were reacted with hydrazine hydrate and give the corresponding 4-amino-3-imino-2-aryl-3,4,8,9-tetrahydro-2(H)-pyrimido[5?,4?:5,6]pyrido[2,1-a]isoquinoline-1-carbonitrile derivatives 6a-c. Refluxing compound 6a in an excess of triethyl orthoformate give 7a. When compounds 6a-c were refluxed with acetic anhydride or benzoyl chloride in pyridine, they afford the corresponding 4-methyl and 4-phenyl derivatives 8a-c and 9a-c, respectively. Compound 6a was refluxed in diethyloxalate and give product 10. Also, the reaction of 6a with C-acylhydrazonoyl halides 13a,b in refluxing chloroform in the presence of triethylamine afford 14a,b. Correct elemental analyses and spectral data (IR, 1H NMR, 13C NMR and MS) confirm the structure of the synthesized compounds.

Cytotoxicity of Aporphine Alkaloids from the Roots of <i>Annona </i><i>R</i><i>eticulata</i> on Human Cancer Cell Lines

Phytochemical and pharmacological activities of Annona reticulata components suggest a wide range of clinical application in lieu of cancer therapy. Present study includes investigation of bioactive constituents from roots of Annona reticulata for cytotoxic properties against different cancer cell lines. Three aporphine alkaloids liriodenine (AAR-01), norushinsunine (AAR-02) and reticuline (AAR-03) isolated from the roots of Annona reticulata. The structures of the compounds were established by 1 HNMR, 13 CNMR and Mass spectral analysis. All the isolated compounds subjected for cytotoxicity evaluation against A-549, K- 562, HeLa, MDA-MB cancer cell lines and normal cell lines (Vero cells) by MTT assay. All the isolated compounds exhibited prominent dose-dependent cytotoxicity against all the cancer cell lines at dilutions 5, 10 and 20 μg/ml, whereas AAR-02 showed strong cytotoxicity against cancer cell lines with IC50 values ranging from 7.4 to 8.8 µg/ml. Simultaneously, the effect of all the isolated compounds against Vero cell lines was lower in comparison with the cancer cell lines. The prominent cytotoxicity of three aporphine alkaloids viz liriodenine (AAR-01), norushinsunine (AAR-02) and reticuline (AAR -03) may be because of isoquinoline moiety in their structures. The appearance of hydroxyl group at C-7 in AAR-02 could be favorable for increased cytotoxicity against cancer cell lines and lower cytotoxicity against Vero cell line seems that the aporphine alkaloids (AAR-01, AAR-02 and AAR-03) may be used as chemopreventive agents in cancer therapy.

Efficient synthesis of [11C]H-1152, a PET probe specific for Rho-kinases, highly potential targets in diagnostic medicine and drug development

A novel PET probe, [11C]H-1152, specific for Rho-kinases, was synthesized efficiently for the first time based on rapid Pd0-mediated C-[11C]methylation using [11C]methyl iodide and a tributylstannyl precursor, giving the isolated radioactivity of 3.8±1.2 GBq (n=3), specific radioactivity of 97±10 GBq μmol−1 (n=3), and high chemical and radiochemical purities (>99%). The decay-corrected radiochemical yield based on 11CH3I was 63±14%. New potentials of a trifluoroacetyl (TFA) group as a tolerant protecting and facile deprotecting group of a secondary amine were demonstrated by highly selective stannylation (via lithiation of isoquinoline moiety using t-C4H9Li) and ready removal by hydroxide ion leaving the arylstannyl moiety intact, respectively. The role of excess hexamethylphosphoric triamide (HMPA) to realize an efficient stannylation of the isoquinoline lithium species is also discussed briefly.

Palladium catalyzed ring opening of furans as a route to α,β-unsaturated aldehydes

Furans may be ring opened via pallado-catalyzed reactions leading to α,β-unsaturated aldehydes and ketones tethered to indole and isoquinoline moieties. Besides their synthetic interest, these fragmentations bring interesting elements into the discussion around the reaction mechanisms involved in palladium C-H activations of electron-rich heterocycles.

Catalytic Asymmetric Allylation of 3,4-Dihydroisoquinolines and Its Application to the Synthesis of Isoquinoline Alkaloids

A catalytic asymmetric allylation of 3,4-dihydroisoquinoline was carried out with allyltrimethoxylsilane-Cu as the nucleophile in the presence of DTBM-SEGPHOS as the chiral ligand to afford corresponding chiral 1-allyltetrahydroisoquinoline derivatives in good yield and stereoselectivity. The allyl adduct thus obtained was applied to the synthesis of several isoquinoline alkaloids such as crispine A and homolaudanosine. The reaction was further used for the synthesis of the isoquinoline moiety of schulzeine A.

Luminescent Cyclometalated Dialkynylgold(III) Complexes of 2‐Phenylpyridine‐Type Derivatives with Readily Tunable Emission Properties

A novel class of luminescent dialkynylgold(III) complexes containing various phenylpyridine and phenylisoquinoline-type bidentate ligands has been successfully synthesized and characterized. The structures of some of them have also been determined by X-ray crystallography. Electrochemical studies demonstrate the presence of a ligand-centered reduction originating from the cyclometalating C^N ligand, whereas the first oxidation wave is associated with an alkynyl ligand-centered oxidation. The electronic absorption and photoluminescence properties of the complexes have also been investigated. In dichloromethane solution at room temperature, the low-energy absorption bands are assigned as the metal-perturbed π-π* intraligand (IL) transition of the cyclometalating C^N ligand, with mixing of charge-transfer character from the aryl ring to the pyridine or isoquinoline moieties of the cyclometalating C^N ligand. The low-energy emission bands of the complexes in fluid solution at room temperature are ascribed to originate from the metal-perturbed π-π* IL transition of the cyclometalatng C^N ligand. For complex 4 that contains an electron-rich amino substituent on the alkynyl ligand, a structureless emission band, instead of one with vibronic structures as in the other complexes, was observed, which was assigned as being derived from an excited state of a [π(C≡CC(6) H(4) NH(2) )→π*(C^N)] ligand-to-ligand charge-transfer (LLCT) transition.

QSAR guided synthesis of simplified antiplasmodial analogs of naphthylisoquinoline alkaloids

Naphthylisoquinoline alkaloids have attracted considerable interest because of their intriguing structure, their unique biosynthetic origin, and their biological activities against several pathogens causing tropical diseases. Their promising pharmacologic properties make them suitable lead structures for new agents, in particular against malaria. Since these natural products are not easy to isolate in sufficient quantities or to synthesize stereoselectively, quantitative structure–activity relationship studies were accomplished to find new antiplasmodial analogs that are structurally related to the naturally occurring naphthylisoquinoline alkaloids, but more easily accessible, more active against Plasmodium falciparum, and, last but not least, less toxic. We report on the synthesis of several simplified compounds by a Suzuki coupling between the naphthalene and the isoquinoline moieties and on their activities against different pathogens causing infectious diseases. Some structures were found to exhibit excellent – and selective – activities against P. falciparum in vitro.

Combinatorial protocol in multiple linear regression/partial least-squares directed rationale for the caspase-3 inhibition activity of isoquinoline-1,3,4-trione derivatives

The caspase-3 inhibition activity of isoquinoline-1,3,4-trione derivatives has been analysed with the topological and molecular features from Dragon software. Analysis of the structural features in conjunction with the biological endpoints in combinatorial protocol in multiple linear regression (CP-MLR) led to the identification of 45 descriptors for modelling the activity. The study clearly suggested the role of rotatable bonds, mean information on the distance degree equality, radial centricity, bond and structural information content of five-order neighbourhood symmetry, atomic van der Waals volumes and the presence or absence of certain structural fragments to optimise the caspase-3 inhibitory activity of titled compounds. The models developed and the participating descriptors advocate that the substituent groups of the isoquinoline moiety hold scope for further modification in the optimization of the caspase-3 inhibitory activity. Analysis of these descriptors in partial least squares (PLS) highlighted their relative significance in modulating the biological response. The selected descriptors are enriched with information corresponding to the activity when compared to the remaining ones.

ChemInform Abstract: Synthesis of Tetra‐ and Penta‐Heterocyclic Compounds Incorporated Isoquinoline Moiety.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and cytotoxic activity of new azepino[3′,4′:4,5]pyrrolo[2,1- a]isoquinolin-12-ones

A series of azepino[3′,4′:4,5]pyrrolo[2,1- a]isoquinolin-12-ones ( 3a–f), that were conformationally restricted analogs of lead compound 2, were designed as potential cytotoxic compounds and synthesized using a radical oxidative aromatic substitution reaction as the key step. Compounds 3a–f were tested on five tumor cell lines to determine the conformational requirements for biological activity of compound 2. The results show that conformational restrictions on compound 2, generating the derivatives 3a– f, do not appreciably reduce the cytotoxic activity of 2, although compound 3d (R = Br) showed good activity against U-251 cells. Preliminary structure–activity relationship studies with these compounds revealed the importance of halogens bonded to the isoquinoline moiety. Additionally, derivatives 3f (R = NO 2) and 3b (R = F) were cytotoxic to PC-3 and K-562 cells. However, none of the azepino[3′,4′:4,5]pyrrolo[2,1- a]isoquinolinones inhibited the enzymatic activity of CDK1/cyclin B, CDK5/p25, or GSK-3.

Synthesis of Tetra- and Pentaheterocyclic Compounds Incorporated Isoquinoline Moiety

7-Amino-2,3-dimethoxy-9-phenyl-5,6,9,6a-tetrahydropyridino[2,1-a]-isoquinoline-8,10-dicarbonitrile 5 was prepared via Michael addition reaction of benzylidenemalononitrile 2 with isoquinoline-1-carbonitrile 1. Reaction of 5 with triethyl orthoformate and formamide led to the formation of the corresponding 4-ethoxymethylene and 4-aminopyrimidine derivatives of benzo[a]quinolizines 6 and 7, respectively. Compound 6 reacted with hydrazine to give imino-amino compound 8. The latter compound reacted with formic acid, triethyl orthoformate, acetic anhydride or benzoyl chloride to give the triazolopyrimidine derivatives 9, 10 and 11, respectively. Compound 8 reacted with hydrazonoyl halides 12, 13 and diethyl oxalate to give triazinopyrimidine and triazolopyrimidine derivatives 16, 17 and 20, respectively.

1-(3-Phenylisoquinolin-1-yl)hydrazine

The title compound, C15H13N3, contains two independent mol­ecules in the asymmetric unit. The isoquinoline moiety and phenyl rings form dihedral angles of 4.38 (2) and 10.14 (3)° in the two independent mol­ecules. The crystal packing is stabilized by N—H⋯N mol­ecular dimers formed across a center of symmetry.

Synthesis of CD-ring structure of cortistatin A, an anti-angiogenic steroidal alkaloid from marine sponge

Stereoselective synthesis of the CD-ring structure of cortistatin A ( 1), a novel anti-angiogenic steroidal alkaloid from Indonesian marine sponge, was achieved. The stereogenic tertiary carbon center bearing the isoquinoline moiety was constructed by 1,3-chiral transfer method using Johnson–Claisen rearrangement of the chiral allylic alcohol 5. Subsequent intramolecular Michael-aldol reaction afforded the targeted trans-hydrindane skeleton with moderate stereoselectivity.

Polybinaphthyls incorporating chiral 2,2′-binaphthyl and isoquinoline moieties by Sonogashira reaction

Polymers P- 1, P- 2, P- 3, P- 4 and P- 5 were synthesized by the polymerization of 5,8-bis(ethynyl)isoquinoline ( M- 1) with ( R)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthyl (( R)- M- 2), ( S)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthyl (( S)- M- 2), ( R)-6,6′-dibromo-2,2′-bisbutoxy-1,1′-binaphthyl (( R)- M- 3), ( S)-6,6′-dibromo-2,2′-bisbutoxy-1,1′-binaphthyl (( S)- M- 3), and rac-6,6′-dibromo-2,2′-bisbutoxy-1,1′-binaphthyl ( M- 4) under Sonogashira reaction, respectively. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV–vis spectroscopy, DSC–TGA, fluorescence spectroscopy, GPC and circular dichroism (CD) spectroscopy. CD spectra of polymers P- 1 and P- 2, P- 3 and P- 4 are almost identical except that they gave opposite signals at each wavelength. The long wavelength CD effect of P- 1 and P- 2 can be regarded as the more extended conjugated structure in the repeating unit and the helical backbone in the polymer chain. All five polymers have strong blue-green fluorescence due to the efficient energy migration from the extended π-electronic structure of the repeating unit of the polymers to the chiral binaphthyl core and are expected to provide understanding of structure–property relationships of the chiral conjugated polymers.

Propagation of Polar Substituent Effects in 1-(Substituted phenyl)-6,7-dimethoxy-3,4-dihydro- and -1,2,3,4-tetrahydroisoquinolines As Explained by Resonance Polarization Concept

[structures: see text] Propagation of inductive and resonance effects of phenyl substituents within 1-(substituted phenyl)-6,7-dimethoxy-3,4-dihydro- and -1,2,3,4-tetrahydroisoquinolines were studied with the aid of 13C and 15N NMR chemical shifts and ab initio calculations. The substituent-induced changes in the chemical shift (SCS) were correlated with a dual substituent parameter equation. The contributions of conjugative (rhoR) and nonconjugative effects (rhoF) were analyzed, and mapping of the substituent-induced changes is given over the entire isoquinoline moiety for both series. The experimental results can be rationalized with the aid of the resonance polarization concept. This means the consideration of the substituent-sensitive balance of different resonance structures, i.e., electron delocalization, and the effect of the aromatic ring substituents on their relative contributions. With tetrahydroisoquinolines, the delocalization of the nitrogen lone pair (stereoelectronic effect) particularly contributes. Correlation analysis of the Mulliken atomic charges for the dihydroisoquinoline derivatives was also performed. The results support the concept of the substituent-sensitive polarization of the isoquinoline moiety even if the polarization pattern achieved via the NMR approach is not quite the same as that predicted by the computational charges. Previously the concepts of localized pi-polarization and extended polarization have been used to explain polar substituent effects within aromatic side-chain derivatives. We consider that the resonance polarization model effectively contributes to the understanding of the polar substituent effects.

How human neuroblastoma cells make morphine

Recently, our laboratory demonstrated that human neuroblastoma cells (SH-SY5Y) are capable of synthesizing morphine, the major active metabolite of opium poppy. Now our experiments are further substantiated by extending the biochemical studies to the entire morphine pathway in this human cell line. L-[1,2,3-13C3]- and [ring-2',5',6'-2H3]dopa showed high isotopic enrichment and incorporation in both the isoquinoline and the benzyl moiety of the endogenous morphine. [2,2-2H2]Dopamine, however, was exclusively incorporated only into the isoquinoline moiety. Neither the trioxygenated (R,S)-[1,3-13C2]norcoclaurine, the precursor of morphine in the poppy plant, nor (R)-[1,3,4-2H3]norlaudanosoline showed incorporation into endogenous morphine. However, (S)-[1,3,4-2H3]norlaudanosoline furnished a good isotopic enrichment and the loss of a single deuterium atom at the C-9 position of the morphine molecule, indicating that the change of configuration from (S)- to (R)-reticuline occurs via the intermediacy of 1,2-dehydroreticuline. Additional feeding experiments with potential morphinan precursors demonstrated substantial incorporation of [7-2H]salutaridinol, but not 7-[7-2H]episalutaridinol, and [7-2H,N-C2H3]oripavine, and [6-2H]codeine into morphine. Human morphine biosynthesis involves at least 19 chemical steps. For the most part, it is a reflection of the biosynthesis in opium poppy; however, there is a fundamental difference in the formation of the key intermediate (S)-reticuline: it proceeds via the tetraoxygenated initial isoquinoline alkaloid (S)-norlaudanosoline, whereas the plant morphine biosynthesis proceeds via the trioxygenated (S)-norcoclaurine. Following the plant biosynthetic pathway, (S)-reticuline undergoes a change of configuration at C-1 during its transformation to salutaridinol and thebaine. From thebaine, there is a bifurcate pathway leading to morphine proceeding via codeine or oripavine, in both plants and mammals.