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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.

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.

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.

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.

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.

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 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.

A new series of 9-deazaxanthine derivatives with various substituents at the heterocyclic system were synthesized and evaluated for their binding affinities for the four human recombinant adenosine receptors, A(1)-A(3) subtypes. A number of the 9-deazaxanthines derivatives 3a-m showed moderate-to-high affinity for hA(2B) receptors, with compound 3f showing a 32-fold selectivity for A(2B) over A(1) and a 2750-fold selectivity for A(2B) over A(2A).

The synthesis of an important set of 3-furfurylxanthine derivatives is described. Binding affinities were determined for rat A(1) and human A(2A), A(2B) and A(3) receptors. Several of the 3-furfuryl-7-methylxanthine derivatives showed moderate-to-high affinity at human A(2B) receptors, the most active compound (10d) having a K(i) of 7.4 nM for hA(2B) receptors, with selectivities over rA(1) and hA(2A) receptors up to 14-fold and 11-fold, respectively. Affinities for hA(3) receptors were very low for all members of the set.

The aza-Diels–Alder reaction of cyclopentadiene with protonated ( S )-phenylethylimine of methyl carboxilate was studied using density functional theory (DFT) at the B3LYP/6-31G(d) level to elucidate the reported stereoselectivity of this reaction. Four independent reaction pathways were found, all of them proceeding through a concerted, asynchronous, mechanism. Inclusion of solvent effects revealed a high exo / endo stereoselectivity that decreases with increasing temperature, in good accordance with the experimental reports.

In order to identify a high-affinity, selective antagonist for the A2B subtype adenosine receptor, more than 40 1,8-disubstituted-3-(3-methoxypropyl) xanthines were prepared and evaluated for their binding affinity at recombinant human adenosine receptors, mainly of the A2A and A2B subtypes. Some of the 1-ethyl-3-(3-methoxypropyl)-8-aryl substituted derivatives 15(a-m) showed moderate-to-high affinity at human A2B receptors, with compound 15d showing A2B selectivity over the other A receptors assayed (A1, A2A, A3) of 34-fold or over. © 2009 Elsevier Ltd. All rights reserved.

The acid-catalyzed 1,4- and 1,3-cycloadditions between methyl glyoxylate oxime ( 1 ) and cyclopentadiene were investigated using various Lewis and/or Bronsted acids at different temperatures in dichloromethane as solvent. Besides the expected new adducts, (±)-methyl [(3- exo )-2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene]-3-carboxylate ( 2 ) and (±)-methyl [(3- endo )-2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene]-3-carboxylate ( 3 ), a third adduct, (±)-methyl (1 R ,4 R ,5 R )-(2-oxa-3-azabicyclo[3.3.0]oct-7-ene)-4-carboxylate ( 4 ), whose formation can be explained by a 1,3-dipolar cycloaddition, was obtained. Yields and product ratios were found to be more dependent on the catalyst than on the temperature; these results and the stereochemistry of the adducts, confirmed by spectroscopic data ( 1 H and 13 C NMR) and by X-ray crystallography, were used to analyze and propose a mechanistic explanation for both cycloadditions.

The asymmetric aza-Diels–Alder reaction of the (1R)-8-phenylmenthyl or (1R)-8-phenylisoneomenthyl glyoxylate-derived N-benzylimine with cyclopentadiene resulted in the enantioselective synthesis of the corresponding pure [(1S,3-exo)-2-benzyl-2-azabicyclo[2.2.1]hept-5-ene]-3-carboxylates (80 or 69% yield, respectively). Reduction of these cycloadducts with LiAlH4 afforded pure (−)-[(1S,3-exo)-2-benzyl-2-azabicyclo[2.2.1]hept-5-en-3-yl]methanol. Furthermore, a reaction sequence based on Barbier–Wieland degradation of both (1S,3-exo)-adducts afforded pure (+)-(1R)-2-benzoyl-2-azabicyclo[2.2.1]heptan-3-one. In the course of the two transformation sequences referred, the chiral auxiliaries were recovered in a virtually quantitative way.

The Diels–Alder reaction of protonated N -benzyl imine of methyl glyoxylate with cyclopentadiene in different solvents gave mixtures of exo / endo adducts. The exo / endo selectivity of the reaction was elucidated by NMR experiments. Theoretical calculations by means of density functional theory (DFT) at the B3LYP/6-31G(d) level have also been performed to elucidate the molecular mechanism of this reaction. The DFT results suggest a highly asynchronous concerted mechanism, which in turn can explain the preferred exo stereoselectivity of the reaction. Inclusion of solvent effects enhances the exo selectivity, and this effect increases with the polarity of the solvent, in good agreement with the experimental findings.

A set of 14 indane carbocyclic nucleosides were synthesized and experimentally assayed for their inhibitory effects in the proliferation of murine leukemia (L1210/0) and human T-lymphocyte (Molt4/C8, CEM/0) cells. The compounds have promising inhibitory activity judging from the IC 50 values obtained for all these cellular lines. Multiple linear regression analysis was then applied to build up consistent QSAR models based on quantum mechanics-derived molecular descriptors. The derived models reproduce well the experimental data of both three cells ( r 2 ≥0.90), display a good predictive power r CV 2 ≥0.86 and are, above all, easily interpretable. They show that frontier-orbital energies and hydrophobicity are mainly responsible for the activity of the synthesized compounds and also, suggest similar mechanisms of action. The final QSAR-models involve only two descriptors: the lowest unoccupied molecular orbital energy and the solvent accessible-hydrophobic surface area, but describe a sound correlation between predicted and experimental activity data ( r 2 =0.931, r 2 =0.936 and r 2 =0.931 for the cells L1210/0, Molt4/C8 and CEM/0, respectively).

Resolution of racemic endo- benzonorbornenol (±)- 4 was performed using Candida antarctica lipase (Novozym® 435) in benzene (50°C/50 hours) with vinyl acetate as the acyl donor to afford (−)- endo -2-benzonorbornenol (−)- 6 and their corresponding (+)- endo -2-benzonorbornenyl acetate (+)- 5 in high e.e.s of up to 99% and workable yields of up to 45–46%.

A group of chiral molybdenum(VI) complexes comprising MoO2Cl2L**, MoO2Cl(THF)L* and MoO2L2* [L**=chiral bis(oxazoline) and L*=chiral 2′-pyridyl alcoholate] have been prepared in good yields by reaction of the solvent substituted complex MoO2Cl2(THF)2 with one or two equivalents of chiral ligand. Optically active aminoalcohols (L*) were obtained by reaction of the appropriate organolithium compound with (−)-menthone, (+)-8-phenylisomenthone, (−)-8-phenylmenthone, (+)-camphor and (−)-thujone. The molybdenum complexes were characterized by multinuclear NMR (1H, 13C, 17O, 95Mo) spectroscopy, IR spectroscopy and elemental analysis. 95Mo-NMR data reflected the donor capability of the organic ligands, whereas 1H-NMR and IR data were comparatively indifferent to the changes in the Lewis base ligand. The complexes were evaluated as catalysts for the asymmetric epoxidation of trans-β-methylstyrene by tert-butylhydroperoxide. The bis(oxazoline) complexes showed good catalytic activity but had low optical yields. Complexes of the type MoO2Cl(THF)L* (L*=chiral 2′-pyridyl alcoholate) also exhibited high catalytic activity and enantiomeric excesses of up to 23%. The corresponding MoO2L2* alcoholate complexes were considerably less active with comparable optical yields.

New, improved and/or specific syntheses of the diastereoisomers of (−)-8-phenylmenthol are described. The configurations of these products, usable as chiral auxiliaries, were confirmed by X-ray diffractometry of their 3,5-dinitrobenzoates.

An efficient preparation of racemic and chiral 2-functionalized-3,5-bis(hydroxymethyl)pyrrolidines is described. The method uses 2-azabicyclo[2.2.1]hept-5-enes, readily obtained from glyoxylates of aliphatic amines and cyclopentadiene, as starting material. The hydroxylation of the double bond followed by the oxidative cleavage of the six-membered ring and in situ reduction of the dialdehyde intermediate gives the title pyrrolidines.

The recently reported compound (+)-(1 R , endo )-2-benzonorbornenol ( 2 ) proved to be an efficient chiral auxiliary in the asymmetric aza-Diels–Alder reaction between cyclopentadiene and the N -benzyl imine of its glyoxylate, which afforded a virtually all- exo mixture of cycloaducts with a 1 S :1 R diastereomeric ratio of 63:37.

(+)-8-Phenylneomenthol 2, the structure of which was confirmed by X-ray analysis of its 3,5-dinitrobenzoate, was efficiently prepared from commercially available (−)-8-phenylmenthol 3 by oxidation with the Sarett reagent, followed by L-Selectride reduction of the (+)-8-phenylmenthone 6 thus formed.

A new, straitghtforward and efficient method for preparing (+)-8-phenyl iso menthol 1 from its diastereomer (+)-8-phenyl isoneo menthol 2 is described. Conversion of 2 to (+)-8-phenyl-2-menthene 5 , followed by oxidation to the corresponding (+)- trans -epoxide 6 and reduction of 6 with LiBEt 3 H afforded 1 in 78% overall yield.