Generation and Reactions of an Octacyclic Hindered Pyramidalized Alkene.

Octacyclo[10.6.1.01,10.03,7.04,9.08,19.011,16.013,17]nonadeca-5,8,14-triene (27), a hindered pyramidalized alkene, has been generated from a diiodide precursor. Contrary to the usual behavior of known pyramidalized alkenes, no Diels-Alder adducts were obtained from the present alkene when it was generated by different standard procedures in the presence of different dienes. However, products derived from the reduction, t-BuLi addition, condensation with the solvent, or dimerization were isolated from these reactions, depending on the conditions used to generate it. No [2 + 2] cross product among this pyramidalized alkene and tricyclo[3.3.1.03,7]non-3(7)-ene was formed when a mixture of the corresponding precursor diiodides was reacted with sodium amalgam. The analysis of selected geometrical and orbital parameters determined from quantum mechanical calculations indicates that the degree of pyramidalization of this alkene and its higher steric hindrance compared with other polycyclic pyramidalized alkenes may explain its peculiar reactivity.

Neuroprotective Effects of the Multitarget Agent AVCRI104P3 in Brain of Middle-Aged Mice.

Molecular factors involved in neuroprotection are key in the design of novel multitarget drugs in aging and neurodegeneration. AVCRI104P3 is a huprine derivative that exhibits potent inhibitory effects on human AChE, BuChE, and BACE-1 activities, as well as on AChE-induced and self-induced Aß aggregation. More recently, cognitive protection and anxiolytic-like effects have also been reported in mice treated with this compound. Now, we have assessed the ability of AVCRI104P3 (0.43 mg/kg, 21 days) to modulate the levels of some proteins involved in the anti-apoptotic/apoptotic processes (pAkt1, Bcl2, pGSK3ß, p25/p35), inflammation (GFAP and Iba1) and neurogenesis in C57BL/6 mice. The effects of AVCRI104P3 on AChE-R/AChE-S isoforms have been also determined. We have observed that chronic treatment of C57BL/6 male mice with AVCRI104P3 results in neuroprotective effects, increasing significantly the levels of pAkt1 and pGSK3ß in the hippocampus and Bcl2 in both hippocampus and cortex, but slightly decreasing synaptophysin levels. Astrogliosis and neurogenic markers GFAP and DCX remained unchanged after AVCRI104P3 treatment, whereas microgliosis was found to be significantly decreased pointing out the involvement of this compound in inflammatory processes. These results suggest that the neuroprotective mechanisms that are behind the cognitive and anxiolytic effects of AVCRI104P3 could be partly related to the potentiation of some anti-apoptotic and anti-inflammatory proteins and support the potential of AVCRI104P3 for the treatment of brain dysfunction associated with aging and/or dementia.

Behavioural effects of novel multitarget anticholinesterasic derivatives in Alzheimer's disease.

The current pharmacological approach to Alzheimer's disease (AD) treatment, mostly based on acetylcholinesterase inhibitors (AChEIs), is being revisited, especially in terms of the temporal frames and the potential benefits of their noncanonic actions, raising the question of whether inhibitors of AChE might also act in a disease-modifying manner. Besides, in the last decades, the pharmacophoric moieties of known AChEIs have been covalently linked to other pharmacophores in the pursuit of multitarget hybrid molecules that are expected to induce long-lasting amelioration of impaired neurotransmission and clinical symptoms but also to exert disease-modifying effects. Our research consortium has synthesized and defined the pharmacological profile of new AChEIs derivatives of potential interest for the treatment of AD. Among these, huprines and derivatives have been characterized successfully. Huprine X, a reversible AChE inhibitor, designed by molecular hybridization of tacrine and huperzine A, has been shown to affect the amyloidogenic process in vitro, and the AD-related neuropathology in vivo in mice models of the disease. More recently, we have shown that a group of donepezil-huprine heterodimers exerts a highly potent and selective inhibitory action on AChE both in vitro and ex vivo, simultaneously interacting with both peripheral and catalytic binding sites, and inhibiting the ß-amyloid aggregation, whereas some levetiracetam-huprine hybrids have been shown to reduce epileptiform activity, neuroinflammation and amyloid burden in an animal model of AD. Here, we summarize the behavioural correlates of these noncanonic actions as assessed in three distinct biological scenarios: middle-age, cognitive deficits associated with ageing and AD-like phenotype in mice. Besides the improvement in the hallmark cognitive symptomatology without inducing side effects, these drugs have shown to be able to modulate emotional and anxiety-like behaviours or to reduce spontaneous seizures, all of them related to the so-called 'behavioural and psychological symptoms of dementia'. Overall, the studies show that these novel multitarget anticholinesterasics exert noncanonic actions providing symptomatic and disease-modifying benefits of potential interest for the management of AD.

Alternative Access to Functionalized 2,8-Ethanonoradamantane Derivatives.

7a-(Methoxycarbonyl)-N-methyl-1,3a,5,6,7,7a-hexahydro-4H-1,4,6-(epiethane[1,1,2]triyl)indene-4,9-dicarboximide has been prepared through a modification of a previous synthetic sequence, in which the benzyloxymethyl hydroxyl protecting group has been replaced by methoxymethyl, to avoid the apparent formation of a benzyl ester derivative as a side product. The overall yield of the new synthetic sequence is comparable to the previous one. Two advantages of the new procedure are: (a) no benzyl ester was formed and (b) a stereoisomeric mixture of syn- and anti-alcohols at the beginning of the synthetic sequence could be separated and the rest of the synthesis could be carried out with the main syn-stereoisomer instead of the corresponding stereoisomeric mixture as it was the case in the previous process. Additionally, several functional 2,8-ethanonoradamantane derivatives have been prepared.

Short Access to Belt Compounds with Spatially Close C=C Bonds and Their Transannular Reactions.

Two domino Diels-Alder adducts were obtained from 3,7-bis(cyclopenta-2,4-dien-1-ylidene)-cis-bicyclo[3.3.0]octane and dimethyl acetylenedicarboxylate or N-methylmaleimide under microwave irradiation. From the first adduct, a C20H24 diene with C2v symmetry was obtained by Zn/AcOH reduction, hydrolysis, oxidative decarboxylation, and selective hydrogenation. Photochemical [2+2] cycloaddition of this diene gave a thermally unstable cyclobutane derivative, which reverts to the diene. However, both the diene and the cyclobutane derivatives could be identified by X-ray diffraction analysis upon irradiation of the diene crystal. New six-membered rings are formed upon the transannular addition of bromine or iodine to the diene. The N-type selectivity of the addition was examined by theoretical calculations, which revealed the distinct susceptibility of the doubly bonded carbon atoms to the bromine attack.

Multigram synthesis and in vivo efficacy studies of a novel multitarget anti-Alzheimer's compound.

We describe the multigram synthesis and in vivo efficacy studies of a donepezil‒huprine hybrid that has been found to display a promising in vitro multitarget profile of interest for the treatment of Alzheimer's disease (AD). Its synthesis features as the key step a novel multigram preparative chromatographic resolution of intermediate racemic huprine Y by chiral HPLC. Administration of this compound to transgenic CL4176 and CL2006 Caenorhabditis elegans strains expressing human Aß42, here used as simplified animal models of AD, led to a significant protection from the toxicity induced by Aß42. However, this protective effect was not accompanied, in CL2006 worms, by a reduction of amyloid deposits. Oral administration for 3 months to transgenic APPSL mice, a well-established animal model of AD, improved short-term memory, but did not alter brain levels of Aß peptides nor cortical and hippocampal amyloid plaque load. Despite the clear protective and cognitive effects of AVCRI104P4, the lack of Aß lowering effect in vivo might be related to its lower in vitro potency toward Aß aggregation and formation as compared with its higher anticholinesterase activities. Further lead optimization in this series should thus focus on improving the anti-amyloid/anticholinesterase activity ratio.

An entry to functionalized 2,8-ethanonoradamantane derivatives.

The synthesis of a functionalized derivative containing the 2,8-ethanonoradamantane carbocyclic skeleton, whose key-step consists of an intramolecular Diels-Alder reaction, is described. Chemoselective reduction of an intermediate enone required protection of the maleimide function through their Diels-Alder adducts with furan.

Expanding the multipotent profile of huprine-tacrine heterodimers as disease-modifying anti-Alzheimer agents.

BACKGROUND: Multifactorial diseases such as Alzheimer's disease (AD) should be more efficiently tackled by drugs which hit multiple biological targets involved in their pathogenesis. We have recently developed a new family of huprine-tacrine heterodimers, rationally designed to hit multiple targets involved upstream and downstream in the neurotoxic cascade of AD, namely ß-amyloid aggregation and formation as well as acetylcholinesterase catalytic activity. OBJECTIVE: In this study, the aim was to expand the pharmacological profiling of huprine-tacrine heterodimers investigating their effect on muscarinic M(1) receptors as well as their neuroprotective effects against an oxidative insult. METHODS: Sprague-Dawley rat hippocampus homogenates were used to assess the specific binding of two selected compounds in competition with 1 nM [(3)H]pirenzepine (for M(1) receptors) or 0.8 nM [(3)H]quinuclidinyl benzilate (for M(2) receptors). For neuroprotection studies, SHSY5Y cell cultures were subjected to 250 µM hydrogen peroxide insult with or without preincubation with some huprine-tacrine heterodimers. RESULTS: A low nanomolar affinity and M(1)/M(2) selectivity has been found for the selected compounds. Huprine-tacrine heterodimers are not neurotoxic to SHSY5Y cells at a range of concentrations from 1 to 0.001 µM, and some of them can protect cells from the oxidative damage produced by hydrogen peroxide at concentrations as low as 0.001 µM. CONCLUSION: Even though it remains to be determined if these compounds act as agonists at M(1) receptors, as it is the case of the parent huprine Y, their low nanomolar M(1) affinity and neuroprotective effects expand their multitarget profile and increase their interest as disease-modifying anti-Alzheimer agents.

On the reaction of 1,3-diphenylisobenzofuran and (2-iodoethynyl)(phenyl)iodonium triflate. A unique case of oxygen transfer from the Diels-Alder adduct to the diene.

Reaction of 1,3-diphenylisobenzofuran (DPIBF) with 2-(iodoethynyl)(phenyl)-iodonium triflate at room temperature gave the expected Diels-Alder adduct, but using an excess of DFIBF (2 equiv.) and performing the reaction at 55 °C or heating at this temperature during the concentration stage, the initial orange solution or product mixture became dark brown and the products 1,2-phenylene-1,2-bis(phenylmethanone) and 2-(3-iodo-1,4-diphenylnaphthyl)(phenyl)iodonium triflate were obtained, which suggests an oxygen transfer between DPIBF and the initial adduct.

Huprines as a new family of dual acting trypanocidal-antiplasmodial agents.

A series of 19 huprines has been evaluated for their activity against cultured bloodstream forms of Trypanosoma brucei and Plasmodium falciparum. Moreover, cytotoxicity against rat myoblast L6 cells was assessed for selected huprines. All the tested huprines are moderately potent and selective trypanocidal agents, exhibiting IC(50) values against T. brucei in the submicromolar to low micromolar range and selectivity indices for T. brucei over L6 cells of approximately 15, thus constituting interesting trypanocidal lead compounds. Two of these huprines were also found to be active against a chloroquine-resistant strain of P. falciparum, thus emerging as interesting trypanocidal-antiplasmodial dual acting compounds, but they exhibited little selectivity for P. falciparum over L6 cells.

Clock/Sleep-Dependent Learning and Memory in Male 3xTg-AD Mice at Advanced Disease Stages and Extrinsic Effects of Huprine X and the Novel Multitarget Agent AVCRI104P3.

A new hypothesis highlights sleep-dependent learning/memory consolidation and regards the sleep-wake cycle as a modulator of ß-amyloid and tau Alzheimer's disease (AD) pathologies. Sundowning behavior is a common neuropsychiatric symptom (NPS) associated with dementia. Sleep fragmentation resulting from disturbances in sleep and circadian rhythms in AD may have important consequences on memory processes and exacerbate the other AD-NPS. The present work studied the effect of training time schedules on 12-month-old male 3xTg-AD mice modeling advanced disease stages. Their performance in two paradigms of the Morris water maze for spatial-reference and visual-perceptual learning and memory were found impaired at midday, after 4 h of non-active phase. In contrast, early-morning trained littermates, slowing down from their active phase, exhibited better performance and used goal-directed strategies and non-search navigation described for normal aging. The novel multitarget anticholinesterasic compound AVCRI104P3 (0.6 µmol·kg-1, 21 days i.p.) exerted stronger cognitive benefits than its in vitro equipotent dose of AChEI huprine X (0.12 µmol·kg-1, 21 days i.p.). Both compounds showed streamlined drug effectiveness, independently of the schedule. Their effects on anxiety-like behaviors were moderate. The results open a question of how time schedules modulate the capacity to respond to task demands and to assess/elucidate new drug effectiveness.

New oxapolycyclic cage amines with NMDA receptor antagonist and trypanocidal activities.

The synthesis of several (1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-benzoxonin-3-yl)amines and related compounds is reported. Several of them display very similar activity to memantine as NMDA receptor antagonists. Several derivatives showed a significant level of trypanocidal activity.

Effect of huprine X on ß-amyloid, synaptophysin and α7 neuronal nicotinic acetylcholine receptors in the brain of 3xTg-AD and APPswe transgenic mice.

BACKGROUND: Several studies implicate acetylcholinesterase (AChE) in the pathogenesis of Alzheimer's disease (AD), raising the question of whether inhibitors of AChE also might act in a disease-modifying manner. Huprine X (HX), a reversible AChE inhibitor hybrid of tacrine and huperzine A, has shown to affect the amyloidogenic process in vitro. In this study, the aim was to investigate whether HX could affect the AD-related neuropathology in vivo in two mouse models. METHODS: Tg2576 (K670M/N671L) (APPswe) and 3xTg-AD (K670M/N671L, PS1M146V, tauP301L) mice were treated with HX (0.12 µmol/kg, i.p., 21 days) or saline at 6-7 months. Human ß-amyloid (Aß) was measured by ELISA, synaptophysin by Western blot and α7 neuronal nicotinic acetylcholine receptors (nAChRs) were analyzed by [(125)I]α-bungarotoxin autoradiography. RESULTS: Treatment with HX reduced insoluble Aß1-40 (about 40%) in the hippocampus of 3xTg-AD mice, while showing no effect in APPswe mice. Additionally, HX markedly increased cortical synaptophysin levels (about 140%) and decreased (about 30%) the levels of α7 nAChRs in the caudate nucleus of 3xTg-AD mice, while increasing (about 10%) hippocampal α7 nAChRs in APPswe mice. CONCLUSION: The two mouse models react differently to HX treatment, possibly due to their differences in brain neuropathology. The modulation of Aß and synaptophysin by HX in 3xTg-AD mice might be due to its suggested interaction with the peripheral anionic site on AChE, and/or via cholinergic mechanisms involving activation of cholinergic receptors. Our results provide further evidence that drugs targeting AChE affect some of the fundamental processes that contribute to neurodegeneration, but whether HX might act in a disease-modifying manner in AD patients remains to be proven.

Synthesis and pharmacological evaluation of (2-oxaadamant-1-yl)amines.

The synthesis of several (2-oxaadamant-1-yl)amines is reported. They were evaluated as NMDA receptor antagonists and several of them were more active than amantadine, but none was more potent than memantine. None of the tested compounds displayed antiviral activity. Two of the derivatives showed a significant level of trypanocidal activity.

Novel donepezil-based inhibitors of acetyl- and butyrylcholinesterase and acetylcholinesterase-induced beta-amyloid aggregation.

A novel series of donepezil-tacrine hybrids designed to simultaneously interact with the active, peripheral and midgorge binding sites of acetylcholinesterase (AChE) have been synthesized and tested for their ability to inhibit AChE, butyrylcholinesterase (BChE), and AChE-induced A beta aggregation. These compounds consist of a unit of tacrine or 6-chlorotacrine, which occupies the same position as tacrine at the AChE active site, and the 5,6-dimethoxy-2-[(4-piperidinyl)methyl]-1-indanone moiety of donepezil (or the indane derivative thereof), whose position along the enzyme gorge and the peripheral site can be modulated by a suitable tether that connects tacrine and donepezil fragments. All of the new compounds are highly potent inhibitors of bovine and human AChE and BChE, exhibiting IC50 values in the subnanomolar or low nanomolar range in most cases. Moreover, six out of the eight hybrids of the series, particularly those bearing an indane moiety, exhibit a significant A beta antiaggregating activity, which makes them promising anti-Alzheimer drug candidates.

Synthesis and absolute configuration of novel N,O-psiconucleosides using (R)-N-phenylpantolactam as a resolution agent.

A series of novel N,O-psiconucleosides has been prepared in both enantiomeric forms by resolution of an advanced racemic synthetic intermediate using (R)-N-phenylpantolactam as a chiral resolution agent. The absolute configuration of all of these compounds has been unequivocally established by chemical correlation with the novel (R)- or (S)-1-methyl-5-phenylpyrrolidine-2,3-dione, prepared from the known (R)- and (S)-1-methyl-5-phenylpyrrolidin-2-one, respectively.

Synthesis and pharmacological evaluation of several ring-contracted amantadine analogs.

The synthesis of several (3-noradamantyl)amines, [(3-noradamantyl)methyl]amines, (3,7-dimethyl-1-bisnoradamantyl)amines, and [(3,7-dimethyl-1-bisnoradamantyl)methyl]amines is reported. They were evaluated against a wide range of viruses and one of them inhibited the cytopathicity of influenza A virus at a concentration similar to that of amantadine. Several of the new polycyclic amines show an interesting activity as NMDA receptor antagonists. A rimantadine analogue displayed significant trypanocidal activity. Moreover, to further characterize the pharmacology of these compounds, their effects on dopamine uptake were also assessed.

Huprine X Attenuates The Neurotoxicity Induced by Kainic Acid, Especially Brain Inflammation.

Huprine X (HX) is a synthetic anticholinesterasic compound that exerts a potent inhibitory action on acetylcholinesterase (AChE) activity, an agonist effect on cholinergic receptors, neuroprotective activity in different neurotoxicity models in vivo and in vitro and cognition enhancing effects in non-transgenic (C57BL/6) and transgenic (3xTg-AD, APPswe) mice. In this study, we assessed the ability of HX (0.8 mg/kg, 21 days) to prevent the damage induced by kainic acid (KA; 28 mg/kg) regarding apoptosis, glia reactivity and neurogenesis in mouse brain. KA administration significantly modified the levels of pAkt1, Bcl2, pGSK3ß, p25/p35, increased the glial cell markers and reduced the neurogenesis process. We also observed that pre-treatment with HX significantly reduced the p25/p35 ratio and increased synaptophysin levels, which suggests a protective effect against apoptosis and an improvement of neuroplasticity. The increase in GFAP (88%) and Iba-1 (72%) induced by KA was totally prevented by HX pre-treatment, underlying a relevant anti-inflammatory action of the anticholinesterasic drug. Our findings highlight the potential of HX, in particular, and of AChEIs, in general, to treat a number of diseases that course with both cognitive deficits and chronic inflammatory processes.

Binding of 13-amidohuprines to acetylcholinesterase: exploring the ligand-induced conformational change of the gly117-gly118 peptide bond in the oxyanion hole.

The acetylcholinesterase (AChE) inhibitory activity of a series of 13-amido derivatives of huprine Y, designed to enlarge the occupancy of the catalytic binding site by mimicking the piridone moiety present in (-)-huperzine A, has been assessed. Although both 13-formamido and 13-methanesulfonamido derivatives are more potent human AChE inhibitors than tacrine and (-)-huperzine A, none of them equals the potency of huprine Y. Molecular modeling studies show that the two derivatives effectively trigger the Gly117-Gly118 conformational flip induced upon binding of (-)-huperzine A, leading to a similar pattern of interactions as that formed by the pyridone amido group of (-)-huperzine A. The detrimental effect on the binding affinity relative to the 13-unsubstituted huprine could be ascribed to a sizable deformation cost associated with the ligand-induced peptide flip. This finding can be interpreted as a mechanism selected by evolution to ensure the preorganization of the functionally relevant oxyanion hole in the binding site of AChE, where residues Gly117 and Gly118 play a relevant role in mediating substrate recognition.

Efficient and selective photogeneration of cholesterol-derived radicals by intramolecular hydrogen abstraction in model dyads.

Three model dyads have been synthesized by esterification of beta- and alpha-cholesterol (Ch) with (S)- and/or (R)-ketoprofen (Kp). The alpha-dyads are efficient photogenerators of the 7-allyl Ch radicals by intramolecular H abstraction. Subsequent cyclization via C-C coupling occurs in a stereoselective way.