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Properly substituted tetrahydrofuran (THF) rings are important building blocks in the synthesis of many natural metabolites. Having reliable procedures to control the stereoselectivity at the THF core while decorating it with different substituents is a fundamental requirement to achieve and fulfill the complexity of nature. We recently reported a new chemical approach to control the stereochemistry in the alkylation and arylation of furanoside derivatives by using a rhenium(V) complex to form an intermediate oxo-carbenium species able to react with proper soft nucleophiles. Here, we describe theoretical calculations, performed at the DFT B3LYP level, to disclose the important mechanistic features which regulate the entire catalytic cycle of the reaction of mono- and disubstituted furanosides with allyltrimethylsilane catalyzed by Re(O)Cl

A chiral organic cage is able to detect the surrogate of 99TcO4− in water, fruit juice and artificial urine medium.

Iron porphyrin methoxy complexes, of the general formula [Fe(porphyrin)(OCH3)], are able to catalyze the reaction of diazo compounds with alkenes to give cyclopropane products with very high effici...

The role of the cyclic 2,3-N,O-carbamate protecting group in directing the selectivity of mannosylation reactions of diacetone- d -glucose, promoted by BSP/Tf2O via α-triflate intermediates, has been investigated through a combined computational and experimental approach. DFT calculations were used to locate the transition states leading to the α or β anomers. These data indicate the preferential formation of the β−adduct with mannosyl donors either equipped with the 4,6-O-benzylidene protection or without it. The synthetic results confirmed this preference, showing in both cases an α/β selectivity of 4:6. This highlights a role for the 2,3-N,O-carbamate in sharp contrast with what described in the case of 2,3-O-carbonate mannosyl donors.

Herein, we present an example of covalent cages, whose flexible framework undergoes extending-shrinking motion under halide control. In the absence of halide anions, the free cage assumes a flattened conformation: the cavity is compressed along the C3 axis passing through the tertiary amines, and the two tribenzylamine platforms are eclipsed. Halide encapsulation promotes a large conformational rearrangement of the cage, involving an extension of the cavity along the C3 axis and shrinkage along the equatorial plane. Interestingly, the rearrangement is accompanied by the pyramidal inversion of the tertiary amines and by the rotation of the tribenzylamine-based platforms, which become staggered. The imidazolium-containing arms wrap around the spherical anion, leading to a racemic mixture of the M and P helical complexes. As expected from the flexible structure of the cage, the switch between the two limit conformations can be repeated for several cycles under alternating chemical stimuli (AgNO3/TBACl). This result is consistent with the low activation barriers determined by computational investigations. These also allowed us to quantify the energy difference between the shrunk and expanded cage conformations and to hypothesize an energetic pathway along which the conformational rearrangement can occur.

Iron porphyrin methoxy complexes, of the general formula [Fe(porphyrin)(OCH3)], are able to catalyze the reaction of diazo compounds with alkenes to give cyclopropane products with very high efficiency and selectivity. The overall mechanism of these reactions was thoroughly investigated with the aid of a computational approach based on density functional theory calculations. The energy profile for the processes catalyzed by the oxidized [FeIII(Por)(OCH3)] (Por = porphine) as well as the reduced [FeII(Por)(OCH3)]− forms of the iron porphyrin was determined. The main reaction step is the same in both of the cases, that is, the one leading to the terminal-carbene intermediate [Fe(Por)(OCH3)(CHCO2Et)] with simultaneous dinitrogen loss; however, the reduced species performs much better than the oxidized one. Contrarily to the iron(III) profile in which the carbene intermediate is directly obtained from the starting reactant complex, the favored iron(II) process is more intricate. The initially formed reactant adduct between [FeII(Por)(OCH3)]− and ethyl diazoacetate (EDA) is converted into a closer reactant adduct, which is in turn converted into the terminal iron porphyrin carbene [Fe(Por)(OCH3)(CHCO2Et)]−. The two corresponding transition states are almost isoenergetic, thus raising the question of whether the rate-determining step corresponds to dinitrogen loss or to the previous structural and electronic rearrangement. The ethylene addition to the terminal carbene is a downhill process, which, on the open-shell singlet surface, presents a defined but probably short-living diradicaloid intermediate, though other spin-state surfaces do not show this intermediate allowing a direct access to the cyclopropane product. For the crucial stationary points, the more complex catalyst [Fe(2)(OCH3)], in which a sterically hindered chiral bulk is mounted onto the porphyrin, was investigated. The corresponding computational data disclose the very significant effect of the porphyrin skeleton on the reaction energy profile. Though the geometrical features around the reactive core of the system remain unchanged, the energy barriers become much lower, thus revealing the profound effects that can be exerted by the three-dimensional organic scaffold surrounding the reaction site., The DFT study of the Fe(porphyrin)(OCH3)-catalyzed cyclopropanation of alkenes by diazo compounds disclosed the profound effects that can be exerted by the ligand environment surrounding the reaction site in the formation of the intermediate terminal iron carbene, consisting in a significative lowering of the energy barrier for its formation.

In this work, we employed for the first time a dinuclear bis[tris(2-aminoethyl)amine] cryptate to obtain the self-assembly of pseudorotaxane structures in an aqueous solution. The goal was achieved by exploiting the well-known affinity of the dicopper azacryptate with diphenyl spacers for the terephthalate anion. In particular, a series of molecular threads were synthesized by appending either alkyl or polyoxyethylene chains on both sides of the terephthalate benzene ring. The obtained dicarboxylic acids were precipitated as sodium salts, and their affinity toward the dicopper azacryptate was determined in a methanol/water mixture (pH 7). Experimental investigations showed that the chains' length and nature have a small impact on the 1:1 binding constants, whose values range between 4.98 and 5.18 log units. Computational studies indicated that the molecular axle is threaded through the azacryptate cavity, with the terephthalate group wedged between the two copper ions, coordinating both of them in the apical position (the one that, in the free azacryptate, is occupied by a water molecule). Compared to the inclusion complex with the plain terephthalate anion, a slight strain was found in the pseudorotaxane structure, induced by the inner chain of the thread inside the cavity. These results may be of great interest in all of the fields of science and technology in which host-guest recognition and molecular cages are applied.

In this work, we combined smartphone sensing with the indicator displacement approach for the determination of trans,trans-muconic acid (i.e.tt-MA), a benzene biomarker, in urine. Dicopper(II) azacryptate was employed as the receptor. The good match of tt-MA with the receptor cavity was suggested by DFT calculations, and confirmed experimentally by UV-vis titrations in buffered aqueous solutions. The binding constant was determined through fluorimetric titrations using the indicator displacement approach. This method also confirmed the high affinity of the azacryptate for tt-MA in artificial and spiked urine samples. A portable device was then obtained by adsorption of the chemosensing ensemble on silica gel using ELISA-like plastic wells as the support. Indicator displacement was detected and quantified by exposing the microplate to a UV-lamp (366 nm) and recording the RGB values with a smartphone. A good correlation was found between the R index values and urinary tt-MA in the occupational concentration range.

In this work, the synthesis of the cannabinoid receptor 1 neutral antagonists 8-chloro-1-(2,4-dichlorophenyl)-N-piperidin-1-yl-4,5-dihydrobenzo-1H-6-oxa-cyclohepta[1,2-c]pyrazole-3-carboxamide 1a and its deaza N-cyclohexyl analogue 1b has led to a deepening of the structure-activity studies of this class of compounds. A series of novel 4,5-dihydrobenzo-oxa-cycloheptapyrazoles analogues of 1a,b, derivatives 1c&ndash, j, was synthesized, and their affinity towards cannabinoid receptors was determined. Representative terms were evaluated using in vitro tests and isolated organ assays. Among the derivatives, 1d and 1e resulted in the most potent CB1 receptor ligands (KiCB1 = 35 nM and 21.70 nM, respectively). Interestingly, both in vitro tests and isolated organ assays evidenced CB1 antagonist activity for the majority of the new compounds, excluding compound 1e, which showed a CB1 partial agonist behaviour. CB1 antagonist activity of 1b was further confirmed by a mouse gastrointestinal transit assay. Significant activity of the new CB1 antagonists towards food intake was showed by preliminary acute assays, evidencing the potentiality of these new derivatives in the treatment of obesity.

The two glycoclusters α- and β-d-mannosylthioureidocalix[4]arenes 1 and 2 in the cone geometry have been submitted to a conformational investigation with the DFT approach at the standard B3LYP/6-31G(d) level and using a water continuum solvent model. After a reasoned choice of the level of calculation and the evaluation of the properties of the monomeric components of 1 and 2, the intrinsic conformational properties of cone calix[4]arenes with orientable groups at the upper rim were thoroughly analyzed. From the possible combinations of the directions that the groups may assume, 10 different geometries derive, all chiral. These geometries are interchangeable through two different processes, named breathing equilibrium and arrow rotation, that allow a dense network connection among them. When the modeling of whole macrocycles 1 and 2 was performed, a huge difference in their conformational behavior that heavily influences the presentation mode of their saccharidic moieties was found.

Three new ureido-pyridazinone derivatives, which are structurally related to the known STAT3 inhibitor AVS-0288, were designed by taking into account the structure–activity relationships determined for several ureido-oxadiazole derivatives previously studied by our group. Their synthesis was first attempted through suitable 5-aminopyridazinone intermediates (6a and 6b), which molecular structures were confirmed by means of X-ray diffraction data on 6a. Amine functionalization was unsuccessful, therefore, an alternative method was devised. Dual-luciferase and AlphaScreen-based assays were used to test their activity. The obtained data were rationalized on the basis of a modeling study, which focused our attention on the geometrical preferences of the ureido moiety. Computational results seem to indicate that both the 1,2,5-oxadiazole ring and the extended ZZ arrangement are essential and probably act in a synergistic way to confer significant activity against STAT3.

Two diazabicyclo analogues of maraviroc, in which the azabicyclooctane moiety is replaced by diazabicyclooctane or diazabicyclononane, were synthesized and tested, through a viral neutralization assay, on a panel of six pseudoviruses. The diazabicyclooctane derivative maintained a significant infectivity reduction power, whereas the diazabicyclononane was less effective. Biological data were rationalized through a computational study that allowed the conformational preferences of the compounds to be determined and a correlation between the inhibitory activity, the bridge length of the bicycle, and the rotational barrier around dihedral angle τ7 to be hypothesized. A high-field NMR analysis supported the modeling results.

International audience; The present study deals with the synthesis and characterisation of C2-symmetrical chiral Fe(iii)(porphyrin)(OMe) catalysts; these catalysts display a totem structure, where each section is assigned to have a specific catalytic activity. The chiral portions of the porphyrin ligand are constituted by amino acid residues, which form a chiral cavity by surrounding both faces of the porphyrin plane, as clearly displayed by the X-ray structure of a free-base porphyrin. The Fe(iii)(porphyrin)(OMe)-catalysed cyclopropanation of α-methylstyrene by diazo compounds occurred with excellent diastereoselectivities and a modest enantiocontrol. Thus, the obtained catalytic results have been rationalised by performing a DFT investigation and will be fundamental in the future modification of the molecular structure of chiral ligands to improve their catalytic performance.

Carbohydrate mimics have been studied for a long time as useful sugar substitutes, both in the investigation of biological events and in the treatment of sugar-related diseases. Here we report further evaluation of the capabilities of inositols as carbohydrate substitutes. The conformational features of an inositol-model of a simplified repeating unit corresponding to the capsular polysaccharide of Streptococcus pneumoniae 19F has been evaluated by computational analysis, and compared to the native repeating unit. The inositol mimic was synthesized, and its experimental spectroscopic data allowed for verification of the theoretical results.

Exemestane, a 3rd-generation aromatase inhibitor, is clinically used in the treatment of breast cancer in postmenopausal women. The key step of the industrial synthetic process, i.e., a dehydrogenation to introduce the Δ1-unsaturation, is normally performed with quinones such as p-chloranil or DDQ. We observed the formation of two different hexacyclic by-products, depending on the quinone used in the oxidation step. These compounds arise from an initial [4+2] cycloaddition between the precursor 6-methylenandrost-4-ene-3,17-dione and the quinone reagent, followed by a twofold dehydrohalogenation (with p-chloranil) or dehydrogenation (with DDQ). The structures of these unprecedented hexacyclic adducts were determined by a combination of mass spectrometry, NMR techniques and crystallographic analysis.

Three new seco-cucurbitane triterpenes, viz. roseic acid (1) and roseolactones A (2) and B (3), all bearing a furan moiety condensed to the B-ring, were isolated from Russula aurora and R. minutula. Their structures were elucidated using 1D and 2D NMR spectroscopy, and ESI HRMS. Compounds 2 and 3 were found to be epimers at C-23. A detailed ab initio theoretical investigation was carried out to assess their relative stereochemistries. The conformations and NMR spectra of the two isomers were calculated, and the results were compared to the experimental data. The new compounds show a bright pink reaction with sulfo-vanillin at room temperature, and they are therefore responsible for the systematically significant reaction performed by mycologists on R. aurora and R. minutula fruiting bodies. A mixture of compounds 2 and 3 was found to be weakly active against HepG2, WISH, and CAKI-1 human tumour cells.

Signal Transducer and Activator of Transcription 3 (STAT3) is a cytoplasmic factor that mediates intracellular signaling commonly generated at cell surface receptors and transmits it to the nucleus. In previous research studies we synthesized several molecules inhibiting STAT3 and among them oxadiazole MD77 and pyridazinone I showed an interesting activity. For the first one, a direct inhibition mechanism was determined, while I interfered within the STAT3 pathway at a different level. In order to discover novel compounds possibly endowed with an improved activity, we decided to merge their scaffolds on the basis of their calculated conformational properties. Therefore we designed and synthesized the chimera diastereomers 3-oxo-N-(4-(trifluoromethyl)phenyl)-2,3,4,4a,5,6-hexahydrobenzo[h]cinnoline-6-carboxamide (1, 2) and 3-oxo-N-(4-(trifluoromethyl)phenyl)-2,3,5,6-tetrahydrobenzo[h]cinnoline-6-carboxamide (3) as racemate and their enantiomeric separation was performed. Modeling studies and theoretical prediction of [α]D values were carried out beside NMR studies which allowed us to assign 1 and 2 relative configurations.

A hydrolytically stable mimetic of the tumour antigen GM3 lactone is used to decorate multivalent scaffolds. Two of them positively interfere on melanoma cell adhesion, migration and resistance to apoptosis (anoikis). Notably, their ability to hamper melanoma-cells adhesion and reduce the metastatic potential is enhanced when the two scaffolds, presenting a different shape, are used in combination. © 2013 Elsevier Ltd.All rights reserved.

Glycosphingolipids (GSLs) are involved in HIV-1 entry. GM-3 ganglioside, a widespread GSL, affects HIV entry and infection in different ways, depending on the concentration, through its anchoring activity in lipid rafts. This explains why the induction of an altered GSLs metabolism was a tempting approach to reducing HIV-1 cell infection. This study assayed the biological properties of a synthetic GM-3 lactone mimetic, 1, aimed at blocking HIV-1 infection without inducing the adverse events expected by an altered metabolism of GLSs in vivo. The mimetic, conjugated to immunogenic protein ovalbumin and multivalently presented, was able to bind the CD4 molecule with high affinity and block its engagement with gp120, thus inhibiting virus entry. Elicited antimimetic antibodies were also able to block HIV-1 infection in vitro, with activity complementary to that observed for 1. These preliminary results show that the use of GSLs mimetics can be a novel promising mode to block HIV-1 infection and that 1 and other GSL mimetics deserve further attention.

International audience; The catalytic activity of the iron(III) C2 chiral porphyrin Fe(2)(OMe) in alkene cyclopropanation is herein reported. The catalyst promoted the reaction of differently substituted styrenes with diazo derivatives with trans-diastereoselectivities and enantioselectivities up to 99:1 and 87 %, respectively. In addition, high TON and TOF values (up to 10 000 and 120 000 h−1, respectively) were observed indicating good activity and stability of the catalyst in optimized experimental conditions. The study of the cyclopropanation reaction revealed that the porphyrin skeleton is composed of two ‘totem’ parts which were independently responsible for the observed enantio- and diastereoselectivities. To further our research we also investigated the catalytic role of the methoxy axial ligand coordinated to the iron atom. The molecular structure of Fe(2)(OMe) was optimized by DFT calculations which were also employed to achieve a better understanding of the mechanistic details of the carbene transfer reaction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The thionation reaction of carbonyl compounds with Lawesson's reagent (LR) has been studied using density functional theory methods and topological analyses. After dissociation of LR, the reaction takes place through a two-step mechanism involving (i) a concerted cycloaddition between one monomer and the carbonyl compound to form a four-membered intermediate and (ii) a cycloreversion leading to the thiocarbonyl derivative and phenyl(thioxo)phosphine oxide. Topological analyses confirmed the concertedness and asynchronicity of the process. The second step is the rate-limiting one, and the whole process resembles the currently accepted mechanism for the lithium salt-free Wittig reaction. No zwitterionic intermediates are formed during the reaction, although stabilizing electrostatic interactions are present in initial stages. Phenyl(thioxo)phosphine oxide formed in the thionation reaction is capable of performing a second thionation, although with energy barriers higher than the first one. The driving force of the thionation reactions is the formation of trimers from the resulting monomers. In agreement with experimental observations, the amides are the most reactive when compared with esters, aldehydes, and ketones and the reaction is slightly influenced by the polarity of the solvent. Whereas for amides and esters substituents have little effect, aldehydes and ketones are influenced by both steric and electronic effects., This work was supported by the Spanish Ministerio de Economia y Competitividad (MINECO) (Project CTQ2013-44367-C2-1-P), by the Fondos Europeos para el Desarrollo Regional (FEDER), and by the Gobierno de Aragon (Zaragoza, Spain, Bioorganic Chemistry Group, E-10). M.A.C. thanks the University of Catania for partial financial support.

Falcipain-2 (FP-2) is a papain-family cysteine protease of Plasmodium falciparum whose primary function is to degrade the host red cell hemoglobin, within the food vacuole, in order to provide free amino acids for parasite protein synthesis. Additionally it promotes host cell rupture by cleaving the skeletal proteins of the erythrocyte membrane. Therefore, the inhibition of FP-2 represents a promising target in the search of novel anti-malarial drugs. A potent FP-2 inhibitor, characterized by the presence in its structure of the 1,4-benzodiazepine scaffold and an α,β-unsaturated methyl ester moiety capable to react with the Cys42 thiol group located in the active site of FP-2, has been recently reported in literature. In order to study in depth the inhibition mechanism triggered by this interesting compound, we carried out, through ONIOM hybrid calculations, a computational investigation of the processes occurring when the inhibitor targets the enzyme and eventually leads to an irreversible covalent Michael adduct. Each step of the reaction mechanism has been accurately characterized and a detailed description of each possible intermediate and transition state along the pathway has been reported.

Three diazabicyclo analogs of BMS-378806, in which theaxial methyl group present on its piperazine ring is replaced by a carbon bridge, were synthesized and tested, through a viral neutralization assay, on a panel of six pseudoviruses. The diazabicyclooctane and-nonane derivatives maintained a significant infectivity reduction power, whereas the diazabicycloheptane derivative was much less effective. A modeling study allowed to relate the antiviral activity to the conformational preferences of the compounds. Moreover, similarly to BMS-378806, theoretical calculations predict the existence of different conformational families corresponding to the possible arrangements at the two planar amido functions of the compounds. High-field 1H NMR spectra confirm these results, as they show two distinct series of signals. A viral neutralization assay on a panel of six HIV-related pseudoviruses allowed the determination of the antiviral activity of three diazabicyclo analogs of BMS-378806, in which the axial methyl group on its piperazine ring is replaced by a carbon bridge. The diazabicyclooctane and-nonane derivatives show a significant infectivity reduction power that is related to their conformational preference.

BMS-378806 (1) is an azaindole derivative known to interfere with the HIV-1 entry process by targeting the viral gp120 envelope glycoprotein and inhibiting its interaction to cellular CD4 receptors. To give a detailed comprehension of its conformational features, a theoretical study of 1 was performed at the B3LYP/6-31G(d) level of calculation. Tenths of populated conformations were located and grouped into four families corresponding to the possible arrangements at the two planar amido functions. In agreement with these results, the high-field 1H NMR spectrum of 1, recorded at 248 K, showed four distinct series of signals easily attributable to each family, thus confirming on experimental grounds the very high degree of conformational mobility of the compound. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Computer simulations of protein models on lattices have been widely used as an aid in the study of protein folding process. Following the suggestion of Raghunathan and Jernigan (1997, Protein Sci. 6:2072-2083) that the cubooctahedral lattice can allow a more realistic representation of proteins than other lattices, we propose here the use of a new set of internal coordinates theta for the description of a protein model on this lattice. An easy procedure for the conversion of the theta coordinates to the Cartesian coordinates is also described. When the Contact Interaction approach, already proposed by us for simulations on square or cubic lattices, was applied to the cubo-octahedral lattice, the system obeyed the correct thermodynamics derived from the definition of energy. Thus, lattice simulations of protein models, in which secondary structure elements such as alpha-helices or beta-strands can be easily identifiable, can be performed.

Alpha series of novel 3,6-diazabicyclo[3.1.1]heptane derivatives 4a-f was synthesized and their affinity and selectivity towards alpha4beta2 and alpha7 nAChR subtypes were evaluated. The results of the current study revealed a number of compounds (4a, 4b and 4c) having a very high affinity for alpha4beta2 (K(i) at alpha4beta2 ranging from 0.023 to 0.056 nM) versus alpha7 nAChR subtypes; among these compounds, the 3-(6-bromopyridin-3-yl)-3,6-diazabicyclo[3.1.1]heptane 4c was found to be the most alpha7alpha4beta2 selective term in receptor binding assays (alpha7alpha4beta2=1295). Moreover, compound 4d also had high affinity for the alpha4beta2 nAChR subtype (K(i)=1.2 nM) with considerably high selectivity (alpha7/alpha4beta2=23300).

A modeling study at the B3LYP/6–31G(d) level was performed on a group of natural odorants. These included α-, β-, and γ-ionones, β-irone, cis- and trans-α- and -γ-irones, and three synthetic α-ionone analogues, all containing an identical E-enone moiety and differing in the endo or exo positions of another double bond and an additional alkyl group at C(2) or at C(13). Data showed a shift of the conformational preference of the butenone chain from an axial or pseudoaxial orientation, as favored in α-ionone and in trans-α- and -γ-irones, to an equatorial or pseudoequatorial orientation, as favored in γ-ionone and in cis-α- and -γ-irones. These changes have been correlated with the enhanced olfactory potencies of the latter set of compounds. In the synthetic α-ionone analogues, bearing an ethyl, propyl, or isobutyl group at C(5) instead of the methyl group present in α-ionone, the hindrance due to this alkyl group does not affect the overall conformational behavior of the molecules. The odor properties seem to be modulated by specific hydrophobic interactions of each carbon of this C(5) alkyl chain with some olfactory receptors rather than by different distributions of the conformational populations.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The catalytic properties of penicillin G acylase (PGA) from Escherichia coli, when used in kinetically controlled N-acylation (kcNa) of cephalosporanic nuclei, can be strongly influenced by the moiety in 3-position of the cephem structure. In the synthesis of Cefonicid (1c), the adsorption of the cephalosporanic nucleus (7-SACA) in the PGA active site appeared sensitively increased by a positive ionic interaction between an arginine (ArgA145) in the enzyme active site and the sulphonic group of the β-lactam structure. Interestingly, when PGA was immobilized on solid supports, any effect depending on the substrate structure resulted minimized; the catalytic properties of this enzyme were affected with different outcomes depending on the type of matrix and binding chemistry. The PGA immobilized on glyoxyl-agarose (hydrophilic support activated with aldehyde groups) resulted in a good catalyst when used in kinetically controlled N-acylation of different cephalosporanic nuclei. This derivatives allow much better Vs/Vh1 (defined as the ratio between the rate of synthesis and the rate of hydrolysis of the acylating agent) than the same enzyme immobilized on Eupergit C, an acrylic hydrophobic supports activated with epoxy groups. The synthetic performances of the Eupergit derivative versus different nuclei were always much poorer if compared with glyoxyl-agarose or the soluble protein. The use of PGA immobilized on glyoxyl-agarose allowed the development of efficient processes for the preparation of Cefazolin in high yield and purity. The results obtained in the optimization of this process are presented.

(Chemical Equation Presented) Conformation analysis and synthesis of 2, a hydrolytically stable mimetic of the tumour antigen, GM3 lactone ganglioside (1 a), is reported (see figure for superimposed images of 1 a and 2). The interaction between 2 and wheat germ agglutinin lectin showed that 2 is a veritable mimetic of a sialyl-containing saccharide. DOPC/DOPE liposomes containing thioether 3 were also prepared and characterized; these could prove to be promising carriers for the production of monoclonal antibodies. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

We synthesized several sulfur isosters of ferulenol and related prenylcoumarins from Ferula communis preliminary to finding whether the antitubercular activity of these natural compounds might be dissociated from their antithrombin activity. Direct thionation of ferprenine, an instance of “diversity-oriented” synthesis, yielded a mixture of three thiocoumarin derivatives. When 4-hydroxy-2-deoxy-2-thiocoumarin was reacted with farnesal and other α,β-unsaturated aldehydes, the isosteric oxygen-sulfur substitution at position 2 surprisingly caused a regiochemical inversion in the tandem Knoevenagel-electrocyclic reaction, prevalently affording the linear adduct. An extensive investigation with variously substituted enals highlighted a competition between Knoevenagel and Michael addition. This result was rationalized by energy calculations that took into consideration steric and electronic factors as well as complex formation with the catalyst.

Roseic acid (Ia) and roseolactones A (IIb) and B (IIc) possessing an unusual furan moiety condensed to the B-ring are isolated from the title fungi.

This paper describes the first detailed computational mechanistic study of the Julia-Kocieński olefination between acetaldehyde (1) and ethyl 1-phenyl-1H-tetrazol-5-yl sulfone (2), considered a paradigmatic example of the reaction between unsubstituted alkyl PT sulfones and linear aliphatic aldehydes. The theoretical study was performed within the density functional approach through calculations at the B3LYP/6-311+G(d,p) level for all atoms except sulfur for which the 6-311+G(2df,p) basis set was used. All the different intermediates and transition states encountered along the reaction pathways leading to final E and Z olefins have been located and the relative energies calculated, both for the reactions with potassium- and lithium-metalated sulfones, in THF and toluene, respectively. We have essentially confirmed the complex multistep mechanistic manifold proposed by others; however, the formation of a spirocyclic intermediate in the Smiles rearrangement was excluded. Instead, we found that this step involves a concerted, though asynchronous, mechanism. Moreover, our calculations nicely fit with the diastereoselectivities observed experimentally for potassium- and lithium-metalated sulfones, in THF and toluene, respectively.

Six new galactoglycerolipid analogs, in which one or two 4-methylpentanoyl or trans-2-butenoyl groups are linked to the 2-O-β- d -galactosylglycerol skeleton, were tested for their anti-tumor-promoting activity using a short-term in vitro assay for Epstein–Barr virus early antigen (EBV-EA) activation. All these compounds were more active than their linear or saturated reference compounds in inhibiting the EBV activation promoted by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), the diester 1-O-(4-methylpentanoyl)-2-O-[6-O-(4-methylpentanoyl)-β- d -galactopyranosyl]-sn-glycerol resulting the most active glycoglycerolipid analog till now tested. Four compounds (three butenoates and one 4-methylpentanoate), when tested in the in vivo two-stage carcinogenesis test, exhibited also inhibitory effects on mouse skin tumor promotion.

The two diastereomeric pairs of acidic amino acids 5-(2-amino-2-carboxyethyl)-4,5-dihydroisoxazole-3-carboxylic acid (8A/8B) and 4-(2-amino-2-carboxyethyl)-5,5-dimethyl-4,5-dihydroisoxazole-3-carboxylic acid (10A/10B) were prepared via a strategy based on a 1,3-dipolar cycloaddition. The four amino acids were tested at ionotropic and metabotropic glutamate receptors. None of the compounds was active, neither as agonists nor as antagonists, at 1 mM on metabotropic receptors (mGluR1, -2, -4, and -5 expressed in CHO cell lines). Conversely, the pair of stereoisomers 8A/8B showed a remarkable affinity, antagonist potency, and selectivity for NMDA receptors, when tested on ionotropic glutamate receptors. The affinity of 8A proved to be 5 times higher than that of diastereomer 8B (K(i) values 0.21 and 0.96 microM, respectively). Furthermore, compounds 8A and 8B exhibited a noteworthy anticonvulsant activity in in vivo tests on DBA/2 mice. Derivative 10A was inactive at all ionotropic glutamate receptors, whereas its stereoisomer 10B displayed a seizable binding to both NMDA and AMPA receptors.

Nicotinic acetylcholine receptors (nAChRs) consist of five protein subunits surrounding a central ion channel. Although a considerable diversity of subunit combinations are possible, it seems that ...

Four new estrone derivatives were isolated after treatment of estrone 3-methyl ether (3-methoxyestra-1,3,5(10)-trien-17-one (3) with tert-butyl hydroperoxide and cobalt acetate. Three of the four steroidal compounds − the 9α-(tert-butylperoxy)-6-one 4, the 9α-hydroxy-6-one 5, and the 9β-hydroxy-6-one 7 − originated from oxidation at the 6- and 9-positions. In contrast, oxidation of 3 to a 9β-(tert-butylperoxy) compound afforded the 8-hydroxy-9-cyclodecanone derivative 6 through a molecular rearrangement involving the cleavage of the 8−9 bond. The structures of the compounds were secured by spectroscopic evidence including COSY, HSQC, and NOESY experiments combined with X-ray crystallographic analysis and molecular modeling studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

B3LYP/6-31G* calculations account for the enhanced reactivity and endo stereoselectivity in the dimerization of the fleeting antiaromatic cyclopentadienone. Secondary orbital interactions promote endo stereoselectivity and a full merging of 4+2 and 2+4 allowed paths in an endo bispericyclic transition structure. Electrostatic effects increase reactivity and selectivity but the driving force to enhanced reactivity is the loss of antiaromaticity in the dimerization TSs while enhanced selectivity derives from the more efficient relief of antiaromaticity in the bispericyclic array.

Glycoglycerolipid analogues lacking the glycerol backbone were prepared through a lipase catalyzed transesterification of beta-D-galactosylethylene glycol. The inhibitory effect of the resultant isomeric hexanoates at the primary alcoholic positions, beta-D-galactosylethylene glycol itself and nonyl beta-D-galactopyranoside, was tested on Epstein-Barr virus early antigen (EBV-EA) activation in Raji cells promoted by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), as a primary screening test for inhibitors of tumor promotion. All the compounds assayed were found to be less active than the reference 2-O-beta-D-galactopyranosylglycerol derivatives, of which they are simplified models, indicating that the anti-tumor-promoting activity is very closely related to the presence of a free hydroxymethylene group on the glycerol-like aglycone moiety.

Stereomeric 3-carboxy-Δ 2 -isoxazoline–cyclopentane amino acids, which represent restricted conformations of glutamic acid, have been prepared through a strategy based on the 1,3-dipolar cycloaddition of ethoxycarbonylformonitrile oxide to a suitably protected 1-amino-cyclopent-2-enecarboxylic acid. These amino acids, assayed at iGluRs and mGluRs, proved to be inactive. The biological data have been accounted for through the comparison of their conformational profile with that of a 3-carboxy-Δ 2 -isoxazolinyl proline (CIP-A) and (±)-1-aminocyclopentane-1,3-dicarboxylic acid.

The dimerization of butadiene has been explored by using DFT methods at the B3LYP level with the 6-311+G** basis set. A concerted bispericyclic TS for the endo pathway and a concerted pericyclic TS for the exo pathway are the lowest passes for the dimerization and occur at almost the same energy thus accounting for the lack of stereochemical preferences in the dimerization. Diradical paths involving two unswitched transoid butadiene moieties are competing and account for the formation of minor amounts of trans-1,2-divinyl cyclobutane and 1,5-cycloctadiene.

The synthesis and pharmacology of two potential glutamic acid receptor ligands are described. Preparation of the bicyclic 3-hydroxy-Δ 2 -isoxazoline-cyclopentane derivatives (±)- 7 and (±)- 8 was accomplished via 1,3-dipolar cycloaddition of bromonitrile oxide to suitably protected 1-amino-cyclopent-3-enecarboxylic acids. Their structure was established using a combination of 1 H NMR spectroscopy and molecular mechanics calculations carried out on the intermediate cycloadducts (±)- 11 and (±)- 12 . Amino acid derivatives (±)- 7 and (±)- 8 were assayed at ionotropic and metabotropic glutamic acid receptor subtypes and their activity compared with that of trans -ACPD and cis -ACPD. The results show that the replacement of the ω-carboxylic group of the model compounds with the 3-hydroxy-Δ 2 -isoxazoline moiety abolishes or reduces drastically the activity at the metabotropic glutamate receptors. Conversely, on passing from cis -ACPD to derivative (±)- 8 , the agonist activity at NMDA receptors is almost unaffected.

In this paper we describe the synthesis of a series of novel 2-[(4-alkylsemicarbazono)-(4-aminophenyl)-methyl]-4,5-methylenedioxyphenylacetic acid alkyl esters (10-19) carrying an alkylsemicarbazono moiety at a benzylic site. The influence of this group on the biological activity was evaluated by testing the corresponding derivatives 20-22 in which the 4-alkylsemicarbazono moiety was removed (compound 20) or its alkylureido portion shifted at position 1 (compounds 21-22). Furthermore, the involvement of the 4-aminobenzyl moiety in the anticonvulsant activity was evaluated by testing derivative 23. The anticonvulsant activity of all compounds was assayed against audiogenic seizures induced in DBA/2 mice. Within this series of derivatives, 2-[(4-aminophenyl)-(4-methylsemicarbazono)-methyl]-4,5-methylenedioxyphenylacetic acid methyl ester (10) proved to be the most active compound. It displayed a potency 5-fold higher than that shown by 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (1, GYKI 52466), a well-known noncompetitive 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptor antagonist. Compound 10 was also effective in suppressing seizures induced in Swiss mice by maximal electroshock (MES) or pentylenetetrazole (PTZ). Furthermore, it antagonized in vivo seizures induced by icv administration of AMPA or kainate (KA). Using the patch-clamp technique in primary cultures of granule neurons we tested compounds 10 and 21 for their ability to modulate currents evoked by KA and 2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl)propionic acid (ATPA). These two derivatives reduced KA and ATPA currents to a larger extent than that shown by reference compound 1. Compounds 10 and 21 were also able to reduce neuronal cell death induced by the application of KA (100 microM).

The configuration at C-3 of the 3α- and 3β-hydroxy metabolites of tibolone was studied by extensive application of one- and two-dimensional 1H and 13C NMR spectroscopy combined with molecular modeling performed at the B3LYP/6–31G(d) level. Using HF and DFT GIAO methods, shielding tensors of the two molecules were computed; comparison of the calculated NMR chemical shifts with the experimental values revealed that the density functional methods produced the best results for assigning proton and carbon resonances. Although steroids are relatively large molecules, the present approach appears accurate enough to allow the determination of relative configurations by using calculated 13C resonances; the chemical shift of pairs of geminal α/β hydrogen atoms can also be established by using calculated 1H resonances. Copyright © 2002 John Wiley & Sons, Ltd.

Three C2-symmetrical chiral porphyrins, derived from α,α,β,β-tetrakis(2-aminophenyl)porphyrin and holding two binaphthyl handles through dimethylene, methylene, or direct connections between the binaphthyl moieties and the amidophenyl pickets, have been submitted to a theoretical study to investigate their conformational properties. The porphyrin with no methylene spacer was shown to be a very rigid molecule, whereas its higher homologues showed a certain degree of conformational freedom resulting in two molecular arrangements that give significant contributions to the equilibrium population of each compound. The effect of complexation with zinc(II) was studied through the modeling of the corresponding complexes as well as the role of two N-methylimidazoles (NMI) coordinating the apical positions of zinc in these complexes. The computational data showed that only one of the two molecular architectures accessible for the free ligands can easily accommodate NMI, indicating that the presence of an additional group on the apical coordination positions selects the geometry most suitable to host this group. Finally, the supposed intermediate radical active species in the cyclopropanation catalyzed by a cobalt(II) porphyrin complex, in which the central metal ion coordinates one NMI and the CHCOOEt carbene, were modeled together with the transition states leading to them. It was shown that the cavity originated by the binaphthyl moiety surmounting the porphyrin is not large enough to host the carbene ethyl group, suggesting the opportunity to increase the size of the cavity in order to confer it hosting capability toward the alkyl group. With the ethyl group outside the cavity, the relatively high mobility of CHCOOEt allows it to assume conformations exposing both the carbene Re and Si faces to the approaching alkene, thus leading to a poorly selective process.