Search

The control of Parkinson's disease (PD) is challenged by the motor and non-motor fluctuations as well as dyskinesias associated with levodopa long-term therapy. As such, pharmacological alternatives to reduce the reliance on this drug are needed. Melanostatin (MIF-1), a positive allosteric modulator (PAM) of D2 receptors (D2R), is being explored as a novel pharmacological approach focused on D2R potentiation. In this work, 3-furoic acid (3-Fu) was successfully employed as an l-proline (Pro) surrogate, affording two potent MIF-1 analogues, methyl 3-furoyl-l-leucylglycinate (4a) and 3-furoyl-l-leucylglycinamide (6a). In this series, the C-terminal carboxamide moiety was found crucial to enhancing the potency and toxicological profile, yet it is not considered a requisite for the PAM activity. Conformational analysis excludes 4a from adopting the claimed type II β-turn. The discovery and validation of 6a as a lead compound open a new avenue for the development of a novel class of anti-Parkinson therapeutics targeting the D2R.

Supplementary Materials: The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/ijms23158271/s1., Cancer is still a challenging disease to treat, both in terms of harmful side effects and therapeutic efficiency of the available treatments. Herein, to develop new therapeutic molecules, we have investigated the anticancer activity of halogenated derivatives of different components of the bioluminescent system of marine Coelenterazine: Coelenterazine (Clz) itself, Coelenteramide (Clmd), and Coelenteramine (Clm). We have found that Clz derivatives possess variable anticancer activity toward gastric and lung cancer. Interestingly, we also found that both brominated Clmd (Br-Clmd) and Clm (Br-Clm) were the most potent anticancer compounds toward these cell lines, with this being the first report of the anticancer potential of these types of molecules. Interestingly, Br-Clm possessed some safety profile towards noncancer cells. Further evaluation revealed that the latter compound induced cell death via apoptosis, with evidence for crosstalk between intrinsic and extrinsic pathways. Finally, a thorough exploration of the chemical space of the studied Br-Clm helped identify the structural features responsible for its observed anticancer activity. In conclusion, a new type of compounds with anticancer activity toward gastric and lung cancer was reported and characterized, which showed interesting properties to be considered as a starting point for future optimizations towards obtaining suitable chemotherapeutic agents., The Portuguese “Fundação para a Ciência e Tecnologia“ (FCT) is acknowledged for funding project PTDC/QUI-QFI/2870/2020, the R&D Units CIQUP (UIDB/00081/2020), GreenUPorto (UIDB/05748/2020), LAQV/REQUIMTE (UIDB/50006/2020), and the Associated Laboratory IMS (LA/P/0056/2020). L. Pinto da Silva acknowledges funding from FCT under the Scientific Employ ment Stimulus (2021.00768.CEECIND). Patricia González-Berdullas acknowledges funding for her postdoctoral position in the framework of project PTDC/QUI/QFI/2870/2020. Carla Magalhães acknowledges FCT for her PhD grant (SRFH/BD/143211/2019). Renato B. Pereira acknowledges PRIMA Foundation (H2020- PRIMA 2018—Section 2, Project MILKQUA) and FCT (PTDC/QUI QFI/2870/2020) for the funding.

Neurodegenerative disorders of the central nervous system are a class of heterogeneous pathologies affecting millions of people worldwide and represent a global health burden in developed and developing countries. Without restorative treatments currently available, research on neuroprotective drugs is considered a health priority. In this study, new analogues of the glycyl-l-prolyl-l-glutamic acid (Glypromate) neuropeptide were designed, synthesized, and biologically evaluated using (1R,3S,4S)-2-azanorbornane-3-carboxylic acid as a hybrid construct of l-proline and l-pipecolic acid. Neuroprotection assays carried out in human neuroblastoma SH-SY5Y cells using 6-hydroxydopamine as a stress inducer showed great percentage of recovery (29.7-40.0%) at 100 μM. Among this series, [(1R,3S,4S)-2-glycyl-2-azanorbornane-3-carbonyl]-l-aspartic acid (2a) stands out with a remarkable percentage of recovery (40.0%, at 100 μM) and safe toxicological profile in SH-SY5Y and human adipose mesenchymal stem cells.

Neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, are a class of heterogeneous pathologies of the central nervous system (CNS) affecting millions of people worldwide. CNS-related pathologies represent a global health burden in developed and developing countries with no curative treatments currently available. Thus, the development of novel multitarget neuroprotective drugs is a health priority. In this work, a bioinspired methodology in solution-phase for the assembly and regioselective conjugation of Glypromate® neuropeptide with active pharmaceutical ingredients (APIs) is described. The main purpose is to design new hybrid molecules which may offer increased systemic resistance of Glypromate® towards proteases and/or allow the controlled release of both APIs and the neuroprotective peptide within CNS. For the synthesis of such peptide-hybrid compounds (R)-1-aminoindane, amantadine, and memantine were selected as APIs for conjugation with Glypromate®. Furthermore, capping strategies are explored to prepare Glypromate® conjugates with more favorable pharmacodynamic profiles by masking polar exposed groups. Overall, this synthetic approach led to the development of a small library of 12 conjugates with improved drug-like properties in comparison with Glypromate®, paving the way for the discovery of novel CNS multitarget drugs. Additionally, by exploring the bis-functionalization of glutamate, the formation of chiral glutarimides is disclosed for the first time employing TBTU as the coupling reagent. This unusual reactivity of TBTU with glutamate offers a new synthetic approach for the preparation of chiral glutarimide alkaloids.

This work describes an improved and greener methodology of solution-phase synthesis for the preparation of Glypromate® (glycyl-L-prolyl-L-glutamic acid, GPE), a potent neuropeptide for applications in neurodegenerative conditions such as Huntington's, Parkinson's and Alzheimer's diseases. This protocol comprises the assembly of the perbenzylated form of Glypromate® [Cbz-Gly-Pro-Glu(OBn)-OBn (5)] from L-proline. Following a tandem sequential peptide coupling strategy, two chemoselective peptide bonds are formed without the need for purifying the intermediates ensuing a one-pot fashion synthesis. EcoScale score and E-factor were selected as the green metrics to assess the environmental impact of the preparation of tripeptide 5 using this protocol. After optimization and application of greener conditions, intermediate 5 was obtained with 95% global yield and 99% purity (NMR, HRMS, and rp-HPLC), with excellent final EcoScale score of 75 out of 100 and global E-factor of 1.8. Glypromate® is achieved by removing N- and C-protecting groups by hydrogenolysis using Pd/C as the catalyst in 98% yield, avoiding chromatographic techniques. Moreover, the protocol ensures stereochemical integrity (determined by VT-NMR and rp-HPLC) and was also successfully applied for the preparation of structurally-related Glypromate® analogues with higher degree of molecular complexity compatible with functionalized amino acids with different side chains. For the first time a one-pot protocol for the assembly of tripeptides with the removal of protecting groups in the same reaction vessel is reported.

This work describes the synthesis and pharmacological evaluation of picolinoyl-based peptidomimetics of melanocyte stimulating hormone release inhibiting factor 1 (MIF-1) as dopamine modulating agents. Eight novel peptidomimetics were tested for their ability to enhance the maximal effect of tritiated N-propylapomorphine ([3H]-NPA) at dopamine D2 receptors (D2R). Methyl picolinoyl-l-valyl-l-alaninate (compound 6b) produced a statistically significant increase in the maximal [3H]-NPA response at 0.01 nM (11.9 ± 3.7%), which is close to the effect of MIF-1 in this assay at same concentration (18.3 ± 9.1%). Functional assays measuring cAMP mobilization in the presence of dopamine corroborate the activity of peptidomimetic 6b as a positive allosteric modulator (PAM) of D2R. In this assay, 6b produced a typical bell-shaped dose-response curve similar to that of the parent neuropeptide (18.3 ± 7.1% for 6b vs 15.4 ± 5.5% for MIF-1, both at 0.1 nM). Dose-response curves for dopamine in the presence of 6b show EC50 (0.33 ± 0.21 μM for 6b vs 0.17 ± 0.07 μM for MIF-1) and Emax (86.0 ± 5.4% for 6b vs 93.6 ± 4.4% for MIF-1) comparable to those of MIF-1, both at 0.01 nM. Furthermore, peptidomimetic 6b was tested for agonist activity at the human D2R and the results show that it displays no intrinsic agonism effect, endorsing its activity as a PAM of D2R. Cytotoxic and neurotoxic assays were performed for peptidomimetic 6b using HEK 293T cells and cortex neurons from 19 day old Wistar-Kyoto rat embryos, respectively, suggesting this analogue displays no toxicity effect in these assays up to 100 μM. Conformational energy minimization for 6b shows that this peptidomimetic cannot adopt the postulated type-II β-turn bioactive conformation, endorsing the possibility of an extended bioactive conformation as claimed by other researchers as a second bioactive conformation of MIF-1. Overall, the pharmacological and toxicological profile of peptidomimetic 6b together with its favorable druglike properties and structural simplicity makes it a potential lead compound for further development and optimization.

This work describes the synthesis and pharmacological evaluation of 2-furoyl-based Melanostatin (MIF-1) peptidomimetics as dopamine D2 modulating agents. Eight novel peptidomimetics were tested for their ability to enhance the maximal effect of tritiated N-propylapomorphine ([3H]-NPA) at D2 receptors (D2R). In this series, 2-furoyl-l-leucylglycinamide (6a) produced a statistically significant increase in the maximal [3H]-NPA response at 10 pM (11 ± 1%), comparable to the effect of MIF-1 (18 ± 9%) at the same concentration. This result supports previous evidence that the replacement of proline residue by heteroaromatic scaffolds are tolerated at the allosteric binding site of MIF-1. Biological assays performed for peptidomimetic 6a using cortex neurons from 19-day-old Wistar-Kyoto rat embryos suggest that 6a displays no neurotoxicity up to 100 μM. Overall, the pharmacological and toxicological profile and the structural simplicity of 6a makes this peptidomimetic a potential lead compound for further development and optimization, paving the way for the development of novel modulating agents of D2R suitable for the treatment of CNS-related diseases. Additionally, the pharmacological and biological data herein reported, along with >20â000 outcomes of preclinical assays, was used to seek a general model to predict the allosteric modulatory potential of molecular candidates for a myriad of target receptors, organisms, cell lines, and biological activity parameters based on perturbation theory (PT) ideas and machine learning (ML) techniques, abbreviated as ALLOPTML. By doing so, ALLOPTML shows high specificity Sp = 89.2/89.4%, sensitivity Sn = 71.3/72.2%, and accuracy Ac = 86.1%/86.4% in training/validation series, respectively. To the best of our knowledge, ALLOPTML is the first general-purpose chemoinformatic tool using a PTML-based model for the multioutput and multicondition prediction of allosteric compounds, which is expected to save both time and resources during the early drug discovery of allosteric modulators., This research was funded by Fundação para a Ciência e Tecnologia (FCT, Portugal), through grants UIDB/50006/2020 (to LAQV-REQUIMTE Research Unit) and for project grants PTDC/BIA-MIB/29059/2017 and PEst-OE/QUI/UI0674/2013. This work was also supported by the Collaborative Project of Genomic Data Integration (CICLOGEN)., The support of Ikerbasque, Basque Foundation for Science and the research grants from Ministry of Economy and Competitiveness, MINECO, Spain (FEDER CTQ2016–74881-P), and Basque government (IT1045–16) are also acknowledged. The financial support (ED431G 2019/02) from the Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2019–2022) and the European Union (European Regional Development Fund—ERDF) is gratefully acknowledged. I.E.S.-D. thanks FCT for the doctoral grant SFRH/BD/93632/2013. X.G.-M. thanks Xunta de Galicia for financial support (GPC2014/003).

Herein we present a new synthesis methodology for the transprotection of the 1-phenylethyl protected tertiary amines to tert-butyloxycarbonyl (Boc) derivatives under exocyclic N–C hydrogenolysis catalyzed by Pd/C. We provide mechanistic insights into the N-dealkylation of hindered tertiary amines under the unrecognized role of tert-butyloxycarbonyl anhydride (Boc2O) as an additive to effectively promote the exocyclic N–C hydrogenolysis of tertiary amines by disclosing the role of Boc2O, which was not fully understood and studied until now. NMR and in silico experiments suggest the formation of a transient charged carbamate as the plausible intermediate. This selective transprotection enabled the development of a robust stereoselective methodology for the preparation of both enantiomers of 2-azanorbornane-3-exo-carboxylates by highly asymmetric aza-Diels–Alder reactions using (−)-8-phenylmenthol (8PM) and (+)-8-phenylneomenthol (8PnM) as chiral auxiliaries.

The conversion of nitroarenes to aminoarenes is of great industrial interest since they are prevalent pollutants in water and aminoarenes are important intermediates in the synthesis of pharmaceuticals, natural products and in bulk chemical production. In this work, two new catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) were prepared by immobilization of gold nanoparticles onto the surface of K10 montmorillonite clay (K10) functionalized with two new l -serine derivative organosilanes. Transmission electron microscopy showed the presence of 4–5 nm gold nanoparticles after catalysis. The reduction reaction of 4-NP to 4-AP at 25 °C, using NaBH4 as reducing agent, led to nearly 100% conversion in only 1 minute, presenting pseudo-first-order rate constants normalized for Au loading of K = 630 and 430 mmol−1 s−1. The catalysts showed high stability, leading to substrate conversions of 95–100% after 10 consecutive cycles, with negligible Au leaching.

Tetracarbonylmolybdenum(0) complexes of the type cis-[Mo(CO)4(L)] containing chiral 7-(1-pyrindanyl) amine ligands were prepared and found to be effective precatalysts for the epoxidation of achiral (cis-cyclooctene) and prochiral (DL-limonene and trans-β-methylstyrene) olefins at 55 °C. Epoxides were the only products formed from cis-cyclooctene (100% yield) and trans-β-methylstyrene (100% selectivity at 82–85% conversion), and the main products formed from DL-limonene (80–82% 1,2-epoxide selectivity at 85% conversion). Characterization of recovered catalysts revealed that the precatalysts were transformed in situ to stable polyoxomolybdate salts containing the β-octamolybdate anion [β-Mo8O26]4−, which was responsible for the catalytic reaction.

In this work, the synthesis of several racemic derivatives of 1-pyrindane as rasagiline analogues is described. The 1-pyrindane moiety was functionalised at C-7 position to afford the respective propargyl and isobutyl ethers, propargyl, isopropyl, n-propyl, and cyclopropyl amines and N,N-dimethyl- and diethylcarbamoyl derivatives. All the new prepared compounds were fully characterised by NMR spectroscopy and mass spectrometry.

(2S,3S,4R)- Dihydroxyhomoprolines were obtained from a six- carbon- atom lactone intermediate obtained from D- erythrose in a short synthesis, by facile operational methodology, in very good overall yields., Thanks are due to Fundacao para a Ciencia e a Tecnologia (FCT) for financial support to the research Unit LAQV/REQUIMTE (UID/QUI/50006/2013), FCT and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support to CQ/UM, and to the NMR Portuguese network (PTNMR, Bruker Avance III 400-Univ. Minho).

Cancer is a very challenging disease to treat, both in terms of treatment efficiency and side-effects. To overcome these problems, there have been extensive studies regarding the possibility of improving treatment by employing combination therapy, and by exploring therapeutic modalities with reduced side-effects (such as photodynamic therapy (PDT)). Herein, this work has two aims: (i) to develop self-activating photosensitizers for use in light-free photodynamic therapy, which would eliminate light-related restrictions that this therapy currently possesses, (ii) to assess their co-treatment potential when combined with reference chemotherapeutic agents (Tamoxifen and Metformin). We synthesized three new photosensitizers capable of self-activation and singlet oxygen production via a chemiluminescent reaction involving only a cancer marker and without requiring a light source. Cytotoxicity assays demonstrated the cytotoxic activity of all photosensitizers for prostate and breast tumor cell lines. Analysis of co-treatment effects revealed significant improvements for breast cancer, producing better results for all combinations than just for the individual photosensitizers and even Tamoxifen. By its turn, co-treatment for prostate cancer only presented better results for one combination than for just the isolated photosensitizers and Metformin. Nevertheless, it should be noted that the cytotoxicity of the isolated photosensitizers in prostate tumor cells was already very appreciable.

In this work, rearrangement reactions subsequent to the oxidation of tertiary amines were studied in 2-(cyanoethyl)-2-azanorbornane/ene systems. [1,2]- and [2,3]-Meisenheimer rearrangements, as well as the Cope elimination reaction, were observed with virtually complete selectivity. It was found that 2-(cyanoethyl)-2-azanorbornanes afford N-hydroxylamines through Cope elimination reactions and 2-(cyanoethyl)-2-azanorbornenes are prone to Meisenheimer rearrangements. In addition, the endo/exo configuration of 2-azanorbornenes plays a key role in the Meisenheimer rearrangement outcome. All the synthesized compounds were fully characterized by NMR spectroscopy and HRMS.

An efficient and straightforward orthogonal methodology was successfully developed to achieve constrained l-prolyl-l-leucylglycinamide (PLG) analogues starting from two proline mimetics based on a 2-azanorbornane scaffold. A preliminary dopamine D2 receptor radiolabeled binding assay with [3H]-N-propylnorapomorphine shows that enantiopurity of PLG peptidomimetics based on 2-azanorbornane is a requirement to achieve statistically significant positive modulators of the D2 receptor. This is the first documented active peptidomimetic of PLG whose bioactivity is not correlated with the C-terminal carboxamide pharmacophore and which cannot adopt the hypothesized type II β-turn conformation.

l -Serine derivatives were covalently immobilized onto three clays with different nature, morphology or crystallite size: K10, which is a chemically-treated montmorillonite; laponite, which is a synthetic clay; and halloysite, which is a natural clay. To achieve that goal, the l -serine derivatives were firstly silylated with the organosilane 3-(triethylsilyl)propyl isocyanate, characterized by mass spectrometry, Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) and then covalently grafted to the clays. The resulting materials were characterized by elemental analyses (N, C and Si), FTIR and 13C solid-state NMR which confirmed the successful grafting of l -serine derivatives to the clays with increasing loading in the following order: halloysite nanoscrolls l -serines onto the clays, involving the reaction between two ethoxy groups of the l -serine based organosilanes and the clay edge/surface silanol groups of laponite and K10. For halloysite, the results suggested that the grafting involved the inner surface Al-OH groups at the internal walls or the Si-OH groups at the edges or external surface defects. It was also found that the remaining ethoxy groups of the T2-grafted organosilanes in K10 were partially hydrolyzed, resulting in free silanol groups or in lateral condensation.

In this work, we describe the reactivity of chlorodiphenylphosphine and its oxide, as well as diphenylphosphine, with some glyoxylate derivative systems: methyl glyoxylate, methyl or 8-phenylneomenthyl glyoxylate oximes, and methyl cyanoformate. By analyzing the reactions outcomes and with the aid of computational chemistry, we propose some reaction mechanisms and molecular rearrangements.

In this work, the enantiopure synthesis of 7-(1-pyrindanyl)propargyl ethers – rasagiline analogues – via chemical and/or enzymatic resolution of the racemic precursor 1-pyrindan-7-ol is described. (R)-Methoxyphenylacetic acid – (R)-MPAA – and (S)-methoxyphenylacetic acid – (S)-MPAA were used as chemical resolution agents, whereas Candida antarctica lipase B (CALB) was employed as kinetic resolution catalyst. The enzymatic resolution was successfully achieved by two different approaches: (1) transesterification of racemic 1-pyrindan-7-ol, which was found to selectively acylate the (R)-enantiomer with high efficiency; (2) hydrolysis of the racemic 7-(1-pyrindanyl)acetate, which was also highly selective to the (R)-enantiomer. The enzymatic hydrolysis was performed in a non-aqueous solvent using a lipase with significant absorbed water content. The configuration of the two enantiomers of 1-pyrindan-7-ol (and consequently of the 7-(1-pyrindanyl)propargyl ethers) were unequivocally determined by X-ray crystallography and/or specific optical rotation.

This study describes a methodological advancement in solution-phase peptide synthesis via the development of a convenient and operational protocol to synthesize oligopeptides in a one-pot three-step cascade method, in which two peptide bonds are introduced chemoselectively. Tri- to hexapeptides were obtained in high global yields (80–95%) with virtually no epimerization as determined via HPLC. The methodology described herein represents a faster, easier and milder approach to the synthesis of peptides, and it operates at equimolar amounts. This protocol comprises the formation of secondary and tertiary amides and is compatible with Z, Boc and Fmoc N-protecting groups as well as the use of D/L and non-proteinogenic amino acids.

Exo-2-azabicyclo[2.2.1]hept-5-enes were obtained by cycloaddition reactions between cyclopentadiene and protonated (S)- and (R)-1-phenylethylimines of (1R,endo)-benzonorbornen-2-yl glyoxylate. The non-natural (1R,endo)-benzonorbornen-2-ol proved to be an efficient chiral auxiliary in these asymmetric aza-Diels–Alder reactions, which afforded only exo-cycloadducts with 1S : 1R diastereomeric ratios of 15 : 85 for (S)-(1-phenylethyl)imine and 93 : 7 for (R)-(1-phenylethyl)imine. The obtained diastereoisomers were effortlessly and efficiently isolated using a chromatographic column. The absolute configuration of all the formed adducts was unequivocally assigned through NMR, specific optical rotation and X-ray data.

A straightforward synthetic approach for the preparation of non N -functionalized isoxazolidines from BF 3 -catalyzed 1,3-cycloaddition reactions between methyl glyoxylate oxime and alkenes is described. Subsequently, isoxazolidines were N -functionalized with three chemically active groups (2-chloroethyl, cyanomethyl and 2-acetoxyethyl), thus allowing the preparation of a wide array of N -functionalized isoxazolidines. The compounds were characterized by means of 1 H and 13 C NMR spectroscopy and mass spectrometry. X-ray analysis was used for stereochemical elucidation.

While photodynamic therapy is known for significant advantages over conventional cancer therapies, its dependence on light has limited it to treating tumors on or just under the skin or on the outer lining of organs/cavities. Herein, we have developed a single-molecule photosensitizer capable of intracellular self-activation and with potential tumor-selectivity due to a chemiluminescent reaction involving only a cancer marker. Thus, the photosensitizer is directly chemiexcited to a triplet excited state capable of generating singlet oxygen, without requiring either a light source or any catalyst/co-factor. Cytotoxicity assays involving the photosensitizer show significant toxicity toward tumor cells, even better than reference drugs, while not inducing toxicity toward normal cells. This work provides a proof-of-concept for a novel type of photosensitizer that eliminates the current restrictions that photodynamic therapy presents regarding tumor size and localization.

A structural study of three synthesized stereoisomeric oximes, (−)-8-phenylmenthyl glyoxylate oxime (8-PMGO), (+)-8-phenylneomenthyl glyoxylate oxime (8-PnMGO), and (−)-8-phenylisoneomenthyl glyoxylate oxime (8-PinMGO), was performed by means of variable temperature 1H NMR spectroscopy, X-ray crystallography, and ab initio calculations. It was found that in 8-PMGO a conformation where the phenyl and oxime moieties are stacked is significantly favored, whereas in the other stereoisomers this preference was not so evident. The conformational differences found between the isomers were used to rationalize the outcome of the reaction (simultaneous 1,3-cycloaddition and aza-Diels–Alder reaction) between the referred oximes and cyclopentadiene, in which the stereoselectivity was evaluated and found to be nicely reproduced by a simple conformational analysis. The global results indicate that the stereoselectivity of the studied oximes, a bit higher for 8-PMGO, originates from their particular conformational distribution, in which the phenyl∙oxime aromatic interaction plays a decisive role.

This work describes that the conventional analysis by Fourier transform infrared spectroscopy of a set of coals grouped by means of multivariate analysis (nonlinear mapping and hierarchical cluster analysis) obtained results that show this methodology is a good approach to summarize and classify coals by their structural relationships and the geochemical processes of their origin.

Enantiopure 4-oxo-pipecolic acid derivatives were obtained by double asymmetric induction aza-Diels–Alder reactions between chiral glyoxylate N-phenylethylimines and Danishefsky's diene mediated by zinc iodide. The key to success was the use of iminoacetates possessing two chiral auxiliaries, N-(S)- or N-(R)-1-phenylethyl and (−)-8-phenylmenthyl or (+)-8-phenylneomenthyl. Adducts were formed in good yields (78–81%), with complete regioselectivity and high diastereoselectivity (87–96%). The absolute configuration of the adducts formed was unequivocally assigned through NMR, specific optical rotation and X-ray data of appropriated derivatives. These cycloadducts can serve as precursors for bioactive piperidinic azasugars and pipecolic acid derivatives.

An efficient and straightforward orthogonal methodology was successfully developed to achieve constrained l-prolyl-l-leucylglycinamide (PLG) analogues starting from two proline mimetics based on a 2-azanorbornane scaffold. A preliminary dopamine D

Covalent conjugation of the small ubiquitin-like modifier (SUMO) to proteins is a highly dynamic and reversible process. Cells maintain a fine-tuned balance between SUMO conjugation and deconjugation. In response to stress stimuli such as heat shock, this balance is altered resulting in a dramatic increase in the levels of SUMO conjugates. Whether this reflects an activation of the conjugation cascade, a decrease in the activity of SUMO-specific proteases (SENPs), or both, remains unknown. Here, we show that from the five human SENPs detected in HeLa cells (SENP1/2/3/6/7) the activities of all but one (SENP6) were largely diminished after 30min of heat shock. The decreased activity is not due to changes in their steady-state levels. Rather, in vitro experiments suggest that these SENPs are intrinsically heat-sensitive, a property most likely emerging from their catalytic domains. Heat shock inactivation seems to be a specific property of SENPs because numerous members of the related deubiquitinase family of cysteine proteases are not affected by this stress condition. Overall, our results suggest that SENPs are particularly sensitive to heat shock, a property that may be important for the adaptation of cells to this stress condition.

β-Cyclodextrin was modified with 11-[(ethoxycarbonyl)thio]undecanoic acid and used as a capping agent, together with mercaptosuccinic acid, to prepare water-stable CdTe quantum dots. The water soluble quantum dot obtained displays fluorescence with a maximum emission at 425 nm (under excitation at 300 nm) with lifetimes of 0.53, 4.8, 181, and 44.1 ns, respectively. The S-βCD-MSA-CdTe can act as a nanoprobe that is due to the affinity of the cyclodextrin moiety for selected substances such as acetylsalicylic acid (ASA) and its metabolites as foreign species. The fluorescence of the S-βCD-MSA-CdTe is enhanced on addition of ASA. Linear calibration plots are observed with ASA in concentrations between 0 and 1 mg/l, with a limit of detection at 8.5 × 10− 9 mol/l (1.5 ng/ml) and a precision as relative standard deviation of 1% (0.05 mg/l). The interference effect of certain compounds as ascorbic acid and its main metabolites such as salicylic, gentisic and salicyluric acid upon the obtained procedure was studied.

Peroxin 5 (PEX5), the peroxisomal protein shuttling receptor, binds newly synthesized peroxisomal matrix proteins in the cytosol and promotes their translocation across the organelle membrane. During the translocation step, PEX5 itself becomes inserted into the peroxisomal docking/translocation machinery. PEX5 is then monoubiquitinated at a conserved cysteine residue and extracted back into the cytosol in an ATP-dependent manner. We have previously shown that the ubiquitin-PEX5 thioester conjugate (Ub-PEX5) released into the cytosol can be efficiently disrupted by physiological concentrations of glutathione, raising the possibility that a fraction of Ub-PEX5 is nonenzymatically deubiquitinated in vivo. However, data suggesting that Ub-PEX5 is also a target of a deubiquitinase were also obtained in that work. Here, we used an unbiased biochemical approach to identify this enzyme. Our results suggest that ubiquitin-specific protease 9X (USP9X) is by far the most active deubiquitinase acting on Ub-PEX5, both in female rat liver and HeLa cells. We also show that USP9X is an elongated monomeric protein with the capacity to hydrolyze thioester, isopeptide, and peptide bonds. The strategy described here will be useful in identifying deubiquitinases acting on other ubiquitin conjugates.

A route to selective functionalization of polyhydroxypyrrolidines is described. The method is based on orthogonal protection/deprotection along the process of synthesis of the referred pyrrolidines, which consist in hydroxylation of the double bond of 2-azabicyclo[2.2.1]hept-5-enes followed by its oxidative cleavage and in situ reduction of the intermediate dialdehyde. The synthesis of a novel N -hydroxypyrrolidine is also described.

The acid catalyzed cycloaddition reaction of methyl glyoxylate oxime with cyclopentadiene (CPD) afforded the corresponding aza-Diels–Alder adducts, the endo and exo isomers of (±)-methyl 2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylates, and as the major product a 1,3-cycloadduct, methyl (1RS,4RS,5RS)-(2-oxa-3-azabicyclo[3.3.0]oct-7-ene)-4-carboxylate. The similar reaction using cyclopentene (CP) provided only the 1,3-cycloadduct methyl (1SR,4RS,5SR)-(2-oxa-3-azabicyclo[3.3.0]octane)-4-carboxylate. The influence of various parameters on the reaction outcome was studied and, based on the results obtained, a mechanism for the formation of both 1,3- and 1,4-cycloadducts is proposed. The structure of all adducts was confirmed by NMR spectroscopic data and/or by X-ray crystallography.

Both exo and endo isomers of (±)-methyl N-diphenylphosphoryl-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate and (±)-methyl N-diphenylphosphoryloxy-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate were dihydroxylated with OsO4. The unexpected formation of (±)-methyl 5,6-dihydroxy-N-diphenylphosphoryl-2-azabicyclo[2.2.1]heptane-3-endo-carboxylate from (±)-methyl N-diphenylphosphoryloxy-2-azabicyclo[2.2.1]hept-5-ene-3-endo-carboxylate is discussed based on NMR analyses and experimental observations. The two N-diphenylphosphoryl dihydroxybicycles are analyzed in terms of their crystalline structure by X-ray crystallography.

Alzheimers disease (AD) is highly complex. While several pathologies characterize this disease, amyloid plaques, composed of the β-amyloid peptide, are hallmark neuropathological lesions in Alzheimers disease brain. Indeed, a wealth of evidence suggests that β-amyloid is central to the pathophysiology of AD and is likely to play an early role in this intractable neurodegenerative disorder. The BACE-1 enzyme is essential for the generation of β-amyloid. BACE-1 knockout mice do not produce β-amyloid and are free from Alzheimers associated pathologies, including neuronal loss and certain memory deficits. The fact that BACE-1 initiates the formation of β-amyloid, and the observation that BACE-1 levels are elevated in this disease provide direct and compelling reasons to develop therapies directed at BACE-1 inhibition, thus reducing β-amyloid and its associated toxicities. In this sense, quantitative structure-activity relationships (QSAR) could play an important role in studying these β-secretase inhibitors. QSAR models are necessary in order to guide the β-secretase synthesis. This work is aimed at reviewing different design and synthesis and computational studies for a very large and heterogeneous series of β-secretase inhibitors. First, we review design, synthesis, and Biological assay of β-secretase inhibitors. Next, we review 2D QSAR, 3D QSAR, CoMFA, CoMSIA and Docking with different compounds to find out the structural requirements. Next, we review QSAR studies using the method of Linear Discriminant Analysis (LDA) in order to understand the essential structural requirement for receptor binding for β- secretase inhibitors.

The cycloaddition between glyoxylate imines possessing two chiral auxiliaries, N-(R)- or N-(S)-1-phenylethyl and 8-phenylmenthyl or 8-phenylneomenthyl, and cyclopentadiene is described. Computational calculations using density functional theory with the Becke, three-parameter, Lee–Yang–Parr functional and the 6-31G(d) basis set were performed to better understand the highly diastereoselective mechanism and the exo-selectivity observed experimentally for these ionic aza-Diels–Alder reactions. Copyright © 2011 John Wiley & Sons, Ltd.

The cycloaddition between protonated glyoxylate imines possessing two chiral auxiliaries, N-(S)- or N-(R)-1-phenylethyl and (-)-8-phenylmenthyl or (+)-8- phenylneomenthyl, and cyclopentadiene is described. The absolute configuration of all adducts formed was unequivocally assigned through NMR, specific optical rotation and X-ray data of appropriated derivatives. Experimental results confirm the highly exoselectivity for these aza-Diels–Alder reactions, single adducts being obtained from combinations of (8PM)-(R-PEA) and (8PNM)-(S-PEA)., Thanks are due to Fundacao para a Ciencia e Tecnologia (FCT) for financial support given to Faculdade de Ciencias do Porto (project PTDC/QUI/67407/2006) and for financial support through the re-equipment program REDE/1517/RMN/2005.

Two new anthocyanin-derived compounds corresponding to the ethylpyranomalvidin-3-glucoside and the pyranomalvidin-3-glucoside dimer linked through a methyl-methine bridge were synthesized for the first time and their structure characterized by LC-DAD/MS and NMR spectroscopy. The latter was obtained in a hydroalcoholic model solution through the reaction of the carboxypyranomalvidin-3-glucoside with ethylpyranomalvidin-3-glucoside and displays a blue/green color in solution.

A fluorescence derivatization method for the quantification of the anthelmintic drug niclosamide in organized media (methyl-β-cyclodextrin) is described. The derivatization reaction is based on a 3 h reduction reaction of the nitro group in niclosamide to an amino group by hydrogenation catalyzed by Pd/C in methanol:ethyl acetate (1:3). The aminoniclosamide exhibits a maximum of fluorescence at 431 nm (excitation at 280 nm) that is markedly enhanced when methyl-β-cyclodextrin is present. The methodology was assessed by the analysis of pure and dosage forms. The method showed a linear range between 0 and 2200 μg L−1 with a limit of detection of 45.7 nΜ and a precision (relative standard deviation) of 4.1% in niclosamide. The effect of various interferents, such as niclosamide, fructose and 2-cyano-6-metoxybenzothiazole, in several tolerance ratios, was investigated respected to aminoniclosamide.

A series of 1-arylnaphthalenes and 1,8-diarylnaphthalenes were synthesized by the Suzuki–Miyaura cross-coupling methodology showing significant differentiation in the yields and selectivity between aryl rings with electron donating (higher yields), and electron withdrawing substituents (lower yields). These results strongly support the relation between the nucleophilicity of the boronate complex and its reactivity, and emphasize the importance of the transmetalation step in the overall efficiency of this cross-coupling reaction. The results obtained with non-symmetric 1,8-diarylnaphthalenes indicate preference for arylation of an already arylated species (the 1-aryl-8-bromonaphthalene intermediate) over mono-arylation of 1,8-dibromonaphthalene. Evidences for the existence of intramolecular Pd⋯π and aromatic interactions in some Pd(II) complexes were found.

Starting from readily available N-benzyl protected methyl 3,5-bis(hydroxymethyl)pirrolidinecarboxylate a number of racemic methyl t-3,t-5-disubstitutedprolinates have been synthesised, thus opening a practical way towards the preparation of a variety of putative proline-mimetics. In this context, N-Boc protected derivatives proved to be better intermediates than their N-benzyl counterparts in terms of cleanness and overall yield of the synthetic procedure.