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Curcumin (CUR) is a natural compound that exhibits anti-inflammatory, anti-bacterial, and other biological properties. However, its application as an effective drug is problematic due to its poor oral bioavailability, solubility in water, and poor absorption from the gastrointestinal tract. The aim of this work is to synthesize monocarbonyl analogs of CUR based on the 9-methyl-9-azabicyclo[3.2.1]nonan-3-one (pseudopelletierine, granatanone) scaffold to improve its bioavailability. Granatane is a homologue of tropane, whose structure is present in numerous naturally occurring alkaloids, e.g., l-cocaine and l-scopolamine. In this study, ten new pseudopelletierine-derived monocarbonyl analogs of CUR were successfully synthesized and characterized by spectral methods and X-ray crystallography. Additionally, in vitro test of the cytotoxicity and anti-inflammatory properties of the synthesized compounds were performed.

Das Alkaloid Pseudopelletierin ist zusammen mit Pelletierin und N-Methylpelletierin in der Rinde des Granatapfelbaums abgelagert. Wahrend Pelletierin und N-Methylpelletierin fur lange Zeit therapeutische Bedeutung als Entwurmungsmittel hatten, ist das Pseudopelletierin als Ausgangssubstanz fur die erste Cyclooctatetraen-Synthese von historischem Interesse. Wir beschreiben seine Isolierung aus der Wurzelrinde von punica granatum und den vollstandigen Satz seiner analytischen Spektren. Die NMR-Spektren und das EI-Massenspektrum werden ausfuhrlich diskutiert und die 13C-chemischen Verschiebungen mit theoretisch ermittelten Werten verglichen. The alkaloid pseudopelletierine is, together with pelletierine and N-methylpelletierine, deposited in the bark of the pomegranate tree. Whereas pelletierine and the N-methylpelletierine were used a long while as vermifuges, pseudepelletierine gained historical interest as starting product of the first cyclooctatetraene synthesis. We describe its isolation from cortex punica granatum and the full set of its analytical spectra. The NMR spectra and the EI-mass spectrum are discussed in detail and the 13C-chemical shifts compared with the theoretically derived data.

A method for the rapid in situ identification of bioactive compounds in fresh plants has been developed using in vivo nanospray coupled to high-resolution mass spectrometry (HR-MS). Using a homemade in vivo nanospray ion source, the plant liquid was drawn out from a target region and ionized in situ. The ionized bioactive compounds were then identified using Q-Orbitrap HR-MS. The accurate mass measurements of these bioactive compounds were performed by full-scan or selected ion monitoring (SIM), and tandem mass spectrometry (MS/MS) was used in the structural elucidation. Without sample pretreatment, 12 bioactive compounds in 7 different plant species were identified, namely, isoalliin in onion; butylphthalide in celery; N-methylpelletierine, pelletierine, and pseudopelletierine in pomegranate; chlorogenic acid in crabapple; solamargine, solasonine, and solasodine in nightshade; aloin and aloe-emodin in aloe; and menthone in mint. This work demonstrates that in vivo nanospray HR-MS is a good method for rapid in situ identification of bioactive compounds in plants.

Background: Punica granatum (family: Lythraceae) is mainly found in Iran, which is considered to be its primary centre of origin. Studies on pomegranate peel have revealed antioxidant, anti-inflammatory, antiangiogenesis activities, with prevention of premature aging and reducing inflammation. In addition to this it is also useful in treating various diseases like diabetes, maintaining blood pressure and treatment of neoplasms such as prostate and breast cancer. Objectives: In this study we identified anti-cancer targets of active compounds like corilagin (tannins), quercetin (flavonoids) and pseudopelletierine (alkaloids) present in pomegranate peel by employing dual reverse screening and binding analysis. Materials and Methods: The potent targets of the pomegranate peel were annotated by the PharmMapper and ReverseScreen 3D, then compared with targets identified from different Bioassay databases (NPACT and HIT’s). Docking was then further employed using AutoDock pyrx and validated through discovery studio for studying molecular interactions. Results: A number of potent anti-cancerous targets were attained from the PharmMapper server according to their fit score and from ReverseScreen 3D server according to decreasing 3D scores. Conclusion: The identified targets now need to be further validated through in vitro and in vivo studies.

Tropinone (8-methyl-8-azabicyclo[3.2.1]octan-3-one) metal (Li, Na, K, Mg) enolates were used to achieve α-alkylation. The reactions, regardless of the metal or conditions used, were low-yielding. N , N -Dimethylhydrazones of tropinone and granatanone (pseudopelletierine, 9-methyl-9-azabicyclo[3.3.1]nonan-3-one) were prepared and α-alkylated using n -butyllithium as the lithiating reagent. Lithium amides, including a polymer-supported lithium amide, were less effective. The reactions were modelled using DFT calculations at the B3LYP 6-31G(d) level and the CPCM solvent model, revealing that the face-selective alkylations of tropinone and granatanone hydrazones favoured the exo -isomers. Granatanone and α-isopropyl tropinone derivatives resisted typical mild hydrolytic hydrazone cleavage (aqueous trifluoroacetic acid) and required more forceful conditions ( p -TsOH, boiling dioxane). Using the hydrazone alkylation strategy, 16 α-alkyl derivatives (benzyl, methyl, propyl, isopropyl, allyl, pentyl, heptyl, p -methoxybenzyl) were prepared in 52–90% yields overall. For the α-alkylated tropinones and granatanones (10 examples), the DFT calculations and experimental thermodynamic distributions in base catalysed equilibrations showed that except for the α-isopropyl derivatives, the endo -isomers were more stable than the exo -isomers and were the major products. For 2-isopropyltropinone, the bulky substituent favoured the exo (axial) position in the bicyclic skeleton. The thermodynamic distribution for the α,α′-dibenzyl tropinone isomers was also evaluated.

The exo,anti/exo,syn-diastereoselectivity of water promoted direct aldol reactions of tropinone and granatanone (pseudopelletierine) is strongly dependent on the amount of water added and aromatic aldehyde used. DFT methods were applied to calculate the free energies of tropinone and granatanone enols, transition states, and isomeric aldol products. A theoretical model was verified by comparison of results from several DFT methods and functionals with experiments. The 6-31g(d)/CPCM method proved most suited to the problem, although all methods tested predicted similar trends. Explicit inclusion of a water molecule bonded to the amino ketones resulted in increased stability of the enol forms. The dependence of the anti/syn-diastereoselectivity on the amount of water used may be rationalized on the basis of change in the polarity of the reaction medium. The predicted stabilities of competing products agreed with experimental results supporting the notion of thermodynamic control. The isomeric products distributions for the aldol reaction of several aromatic aldehydes in solventless (neat) conditions were accurately calculated from free energies of the aldol addition step in the gas phase using B3LYP/6-31g(d) method and in aqueous conditions using the CPCM-B3LYP/6-31g(d) model. Our methodology can be useful for predicting the outcome of this type of aldol reactions.

Experimental diastereoselectivities of the direct solvent-less (neat) aldol reactions of tropinone (8-methyl-8-azabicyclo[3.2.1]octan-3-one) and granatanone (pseudopelletierine, 9-methyl-9-azabicyclo[3.3.1]nonan-3-one) in the presence of catalytic amounts of water are most accurately reproduced by thermodynamic distributions of isomeric products calculated in the gas phase at the B3LYP/6-31g(d) level of theory. Less than 30% systematic errors, on average, exist in the predicted anti / syn -diastereomeric ratio ( dr ) for the solvent-less reaction of tropinone with several aromatic aldehydes. The CPCM-B3LYP/6-31g(d) method reproduces the anti / syn -diastereomeric ratio of the aqueous aldol reaction of tropinone with several aromatic aldehydes with reasonable deviation (0–88%), excellent (0–10)% agreement was found for the reactions of tropinone and granatanone with benzaldehyde. Qualitatively satisfactory agreement was also found for dr values in different solvents (DMF, THF, and Et 3 N). The density functional theory (DFT) results support the notion of the thermodynamic control of the reaction.

Tropane (8-methyl-8-azabicyclo[3.2.1]octane) and granatane (9-methyl-9-azabicyclo[3.3.1]nonane) derivatives undergo fast N-methyl inversion. The distribution of axial and equatorial N-methyl invertomers of protonated and free amine forms in aqueous and methanol solutions was studied by room and low temperature NMR spectroscopy on tropinone, tropine, granatan-3-one (pseudopelletierine or pseudopelletrierin) and α-granatan-3-ol. Theoretical (DFT) distributions in both gas phase and solutions are also reported. Applicability of the computational model for the studied system was verified by comparison with invertomer distributions inferred from inverse-gated 13C NMR experiments. Among the tested functionals, the BH&HLYP/cc-pVDZ method yields the best agreement with experiment. Moreover, accounting for orbital relaxation upon immersion in the solution was found to be of importance in order to properly reproduce observed distributions.

Tropane, tropinone, pseudopelletierine and cocaine were oxidized in situ in a nuclear magnetic resonance (NMR) tube providing mixtures of exo/endo N-oxides. Observed (13)C chemical shifts were correlated with values calculated by gauge-including atomic orbitals density functional theory (DFT) OPBE/6-31G* method using DFT B3LYP/6-31G* optimized geometries. The same method of (13)C chemical shift calculation was applied on series of methyl-substituted 1-methylpiperidines and their epimeric N-oxides described in literature. The results show that using this undemanding calculation method enables assignment of configuration of N-O group in N-epimeric saturated heterocyclic N-oxides. The approach enables assigning of the configuration with high degree of certainty even if NMR data of only one isomer are available. An improved method of in situ oxidation of starting amines in an NMR tube is also described.

Granatanone (granatan-3-one, 9-methyl-9-azabicyclo[3.3.1]nonan-3-one, pseudopelletierine or pseudopelletrierin) undergoes deprotonation with lithium amides giving a lithium enolate, which reacts with aldehydes diastereoselectively giving exclusively exo isomers and anti/syn selectivity up to 98:2. Granatanone can be enantioselectively lithiated by chiral lithium amides and the resulting non-racemic enolate can be reacted with aldehydes giving aldols with enantiomeric excess up to 93% (99% ee after recrystallization). The absolute and relative configuration of the aldol products was determined by NMR spectroscopy and X-ray analysis. Granatanone; aldol reaction; asymmetric synthesis; enantioselective deprotonation; chiral lithium amide.

Direct aldol reactions of 4-methyl-1-piperidone, tropinone and granatanone (pseudopelletierine) take place spontaneously in the presence of water without any catalyst or additional reagents. The anti / syn -diastereoselectivity of the aqueous aldol reaction depends on the amount of water used. The syn -selectivity of the reaction is probably due to the thermodynamic control. Excellent atom economy and low E factors together with anti -selectivity as high as 98:2 for the tropinone aldol were obtained.

In recent literature doubts are expressed about the accepted structure of the anthelmintic substance pelletierine, one of the four alkaloids said to occur in the bark of the pomegranate tree (Punica granatum L.) It has been suggested that the “pelletierine” of the literature is in reality isopelletierine, which would reduce the number of alkaloidal components to three. The present investigation reports on the analyses by means of partition chromatography on paper of two samples of commercial “pelletierine sulphate” and of an extract made of pomegranate bark. Four (or five) spots were found, three of which had RF-values identical with those of synthetic pseudopelletierine, d,l-isopelletierine and d,l-methylisopelletierine. This is a convenient way of establishing the presence of these three compounds in pharmaceutical “pelletierine” preparations and of establishing the presence of one (or two) more substances not yet identified.

Amyloid β(1-40) peptide was immobilized on an Au-colloid modified gold electrode and an electrochemical impedance spectroscopy (EIS) system was elaborated for determining the association constants, Ka, between small molecular ligands and the peptide. The changes in the resistance of the modified electrode layer with deposited Aβ(1-40) peptide were measured with EIS in relation to a series of concentrations of the ligands studied. The association constants were calculated from Langmuir isotherms. The method is sensitive, reproducible and consumes only very little amounts of interacting species. The method was applied to determine the affinity of a series of pyridine and piperidine derivatives, mainly alkaloids of a known ability, to cross the blood-brain barrier. Along with nicotine and its main metabolite cotinine, the following agents were taken for the study: anabasine, arecoline, coniine, lobeline, pseudopelletierine, trigonelline, as well as pyridine and piperidine themselves. For the sake of comparison, two vitamins were also subjected to the study: ascorbic acid and pyridoxine. There was no association of these vitamins, which were tested as a negative control. For the compounds studied, a strong association with Aβ(1-40) was determined with Ka ranging from 1.7 x 107 M-1 for (±)- anabasine to 2.3 x 108 M-1 for arecoline hydrobromide. As a positive control, a well known amyloid specific binder, Congo Red, was tested, displaying Ka equal to 3.7 x 108 M-1.

A rotational spectroscopy investigation has resolved the conformational equilibrium and structural properties of the alkaloid pseudopelletierine. Two different conformers, which originate from inversion of the N-methyl group from an axial to an equatorial position, have been unambiguously identified in the gas phase, and nine independent isotopologues have been recorded by Fourier-transform microwave spectroscopy in a jet expansion. Both conformers share a chair-chair configuration of the two bridged six-membered rings. The conformational equilibrium is displaced towards the axial form, with a relative population in the supersonic jet of Naxial /Nequatorial ≈2/1. An accurate equilibrium structure has been determined by using the semiexperimental mixed-estimation method and alternatively computed by quantum-chemical methods up to the coupled-cluster level of theory. A comparison with the N-methyl inversion equilibria in related tropanes is also presented.

Direct aldol reactions of 4-methyl-1-piperidone, tropinone and granatanone (pseudopelletierine) take place spontaneously in the presence of water without any catalyst or additional reagents. The anti / syn -diastereoselectivity of the aqueous aldol reaction depends on the amount of water used. The syn -selectivity of the reaction is probably due to the thermodynamic control. Excellent atom economy and low E factors together with anti -selectivity as high as 98:2 for the tropinone aldol were obtained.

The current methods for tropane alkaloid chromatographic separation and determination are summarised. The alkaloids included are: the medicinally applied tropic acid esters hyoscyamine and scopolamine and their derivatives, cocaine and derivatives, the metabolites and degradation products of these compounds occurring in plant material, calystegines as nortropane alkaloids, anatoxins as homonortropane alkaloids, pelletierines and pseudopelletierines as alkaloids with isomeric structures. Developments in GC, HPLC, CE and TLC are presented and the advantages of each method for plant analysis are discussed. A summary for each chromatographic method lists the instrumentation and parameters applied for tropane alkaloids.

Direct aldol reactions of tropinone and granatanone (pseudopelletierine) with aromatic aldehydes were promoted by the presence of water. The anti–syn-diastereoselectivity depended on the amount of water used or on the possibility of product precipitation from the reaction mixture. Some of the reactions showed excellent atom economy, a low E factor, and high diastereoselectivity (up to 98%). In several cases ‘seeding’ with the anti isomer, used to induce the deposition of solid products, improved the conversion (up to 1.8 times) and the anti–syn ratio (up to 98:2). The applicability of spontaneous direct aldol reactions in the presence of water was also extended to N-alkyl nortropanones or norgranatanones using an aqueous–organic medium. However, under these conditions only the exo,syn isomers of the N-substituted aldols were obtained. The syn-selectivity for the tropane- and granatane-related aldols is specific for water-promoted reactions and results from thermodynamic control.

The enzymes N-methylputrescine oxidase (MPO), the tropine-forming tropinone reductase (TRI), the pseudotropine-forming tropinone reductase (TRII), the tropine:acyl-CoA transferase (TAT) and the pseudotropine:acyl-CoA transferase (PAT) extracted from transformed root cultures of Datura stramonium and a Brugmansia candida x aurea hybrid were tested for their ability to accept a range of alternative substrates. MPO activity was tested with N-alkylputrescines and N-alkylcadaverines as substrates. TRI and TRII reduction was tested against a series of N-alkylnortropinones, N-alkylnorpelletierines and structurally related ketones as substrates. TAT and PAT esterification tests used a series of N-substituted tropines, pseudotropines, pelletierinols and pseudopelletierinols as substrates to assess the formation of their respective acetyl and tigloyl esters. The results generally show that these enzymes will accept alien substrates to varying degrees. Such studies may shed some light on the overall topology of the active sites of the enzymes concerned.

TpMo(CO)2(5-oxo-η3-pyranyl) and TpMo(CO)2(5-oxo-η3-pyridinyl) complexes 1 and 2 (Scheme 1, Tp = hydridotrispyrazolylborate) and their progeny have been developed as organometallic enantiomeric scaffolds for the asymmetric construction of a wide variety of heterocyclic systems.1 Readily available and easily synthesized,2 single enantiomers of these simple air-stable organometallic π-complexes function as scaffolds from which widely differing families of complex organic structures can be elaborated in an enantiospecific fashion. The organometallic nature of these enantiomeric scaffolds provides opportunities to implement conceptually unique synthetic design strategies. Herein is described one such strategy: a new molybdenum-mediated semipinacol rearrangement delivering α-quaternary pyranyl and pyridinyl systems that, when coupled sequentially with a molybdenum-mediated intramolecular 1,5-“Michael-like” reaction of 5-oxopyridinyl molybdenum complexes,1m can provide a novel enantiocontrolled entry to heteroatom-bridged [3.3.1]bicyclic systems bearing quaternary centers3,4,5 adjacent to the ring heteroatom (Scheme 1). The concept is highlighted via a synthesis of the azabicyclo[3.3.1]nonane natural product, (-)-adaline.6 Adaline possesses the 9-azabicyclo[3.3.1]nonane skeleton common to several insect- and plant-derived alkaloids, including pseudopelletierine,7 (+)-euphococcinine,8 and porantherine.9 This structure is a higher homolog of the medicinally-important tropane skeleton. A number of racemic10 and enantiospecific syntheses11 of adaline have been reported.

Pyrolytic decomposition of the sodium salt of pseudopelletierine tosylhydrazone in diglyme gave 80% yield of 9-methyl-9-azatricyclo[3.3.1.03,7]nonane (IIIa), while the decomposition in ethylene glycol afforded IIIa (11%) and 9-methyl-9-azabicyclo-[3.3.1]nonene-2 (IV) (35%) and the pyrolysis without solvent gave IIIa (53%) and IV (19%). The photolytic decomposition in ether gave also IIIa (30·3%) and IV (33·3%), but in this case, together with 1-azatricyclo[4.3.0.13,9]nonane (V) (6·1%) and 9-methyl-9-azatricyclo[3.3.1.01,3]nonane (VI) (4·3%). The Hofmann degradation of the methiodide (VIIa) of IIIa afforded 7-dimethylaminobicyclo[3.3.0]octene-2 (VIII) which was further converted to bicyclo[3.3.0] octene-2 (XII) by repeated Hofmann degradation after the hydrogenation. IIIa was converted to 9-azatricyclo[3.3.1.03,7]nonane (IIIc) via an N-oxide (XIII), followed by an N-acetyl derivative (IIIb), and also by direct oxidation of IIIa with mercuric acetate. Bromination of IIIa and VIIa afforded the corresponding perbromides VIIb and VIIc respectively.

The pKa values of pseudopelletierine (1), 10-methyl-3,10-diazabicyclo[4.3.1]decan-4-one (2), 10-methyl-3, 10-diazabicyclo[4.3.1]decane (3), 6,8-exo-ethanopseudopelloetierine (4), 7,9-exo-ethano derivatives 5 and 6 of 2 and 3 were measured potentiometrically in water-methyl cellosolve (20 : 80 v/v) at 20°C. The conformational problems in the 3,10-diazabicyclo[4.3.1]decane system were discussed based on the observed pKa′ (pKmcs) values. The characteristic conformational behavior of the monocation (7) of 3 was suggested by the higher value of its pKmcs than of 6.

From a comparison of the physical properties, pH values, and on the basis of chemical genesis it is suggested that the N-methyl-granatoline obtained by the reduction of pseudopelletierine with sodium and alcohol is sterically related to pseudotropanol. The isomeric N-methylgranatoline obtained by catalytic hydrogenation is placed in the same steric configuration as tropanol.

A new synthesis of pseudopelletierine is presented in which the diethyl ester of lobelinic acid was subjected to a Dieckmann type condensation to yield carbethoxy- pseudopelletierine which on hydrolysis and decarboxylation gave pseudopelletierine.A total synthesis of lobelinic acid was also accomplished by reduction of pyridyl-2,6-diacetic acid dianilide, followed by hydrolysis to give norlobelinic acid which was methylated by treatment with formaldehyde and formic acid to give lobelinic acid.Several new compounds prepared include pyridyl-2,6-diacetic acid diethyl ester hydrochloride; norlobelinic acid, its anilide and its dimethyl and diethyl esters as hydrochloride salts; and dimethyl and diethyl esters of lobelinic acid as hydrochloride salts.

The preparation and characterization of the tropic acid esters of tropan-3β-ol and granatan-3α and 3β-ol are reported. A rapid synthesis of pseudopelletierine is described.

The biosynthesis of isopeletierine [1-(2-piperidyl)propan-2-one], N-methylisopelletierine, and pseudopelletierine (9-methyl-9-azabicylo[3,3,1]nonan-3-one) in intact Punica granatum plants has been studied. N-Methylisopelletierine is shown to be derived from lysine and acetate. Acetate is shown to be the precursor of the three-carbon unit in isopelletierine and pseudopelletierine. N-Methylisopelletierine is shown to be the immediate precursor of psueudopelletierine.The derivation of anaferine from lysine and acetate has been demonstrated in intact Withania somnifera plants. Isopelletierine has also been shown to be a precursor of anaferine.

The oxidation of N-methyl groups in pseudo-pelletierine and tropinone to N-formyl groups by a photochemical reaction involving singlet oxygen is described.