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Immunotherapy of tumors and of melanoma in particular has a long history, and recently this therapeutic approach found a reliable scientific rationale. This biological therapy aims to teach the patients immune system to recognize the antigens expressed on tumor cells and destroy them, leaving normal cells intact. The success of this therapy highly depends on the selection of target antigens that are essential for tumors growth and progression. The overexpression of GM3 ganglioside 1 and especially the expression of its metabolite GM3 lactone 2 characterize murine and human melanomas, playing an important role in tumor progression and making such self-antigens potential targets for the immunotherapy of these neoplasms. Although more immunogenic than its precursor, GM3 lactone 2 is unsuitable to be used in immunotherapy as a melanoma-associated antigen (MAA) because it is unstable under physiological conditions. We designed and synthesized the hydrolytically stable mimetic 3, which is remarkably simpler than the native lactone 2; after conjugation of 3 to the protein carrier keyhole-limpet hemocyanin (KLH), the obtained glycoprotein 5 was used as the immunogen in vivo to successfully elicit specific antimelanoma antibodies. In fact, no appreciable binding to GM1 was observed. Capitalizing on the stability and on the reduced structural complexity of mimetic 3, the immunostimulant 5 we report represents a new promising synthetic glycoconjugate for the immunotherapy of melanoma. © 2010 American Chemical Society.

A regio- and stereoselective didehydrodimerization procedure, whose key step involves the anodic oxidation, allows the conversion of β-anilinoacrylic alkaloids belonging to the Aspidosperma class, typified by tabersonine (1) and its 3-oxo derivative 2, into the hitherto unknown 16,10′-didehydro dimers 3 and 7, respectively.

Methyl 6-O-butyryl-α-D- and L-glucopyranosides and methyl 6-deoxy-α-D- and L-glucopyranosides have been submitted to lipase catalyzed butyrylation, using porcine pancreatic, Candida cylindracea, and Pseudomonas cepacia lipases in organic solvents. The influence of the orientation of the secondary hydroxyl groups on the regioselectivity of the butyrylation is discussed.

The X-ray structure of muscarone analogues 3 and 4 was determined and compared with that of muscarone (1, iodide and picrate salts), muscarine 2, dioxolane 5, oxathiolane 6, and tetrahydrofuran 7. In order to better define the pharmacological stereoselectivity of muscarone, the conformational profiles of compounds 1, 2, 3, and 5 were analyzed using Allinger's MM2(85) program or, in the case of 4, by 1H NMR spectroscopy. The conformation of the ring in 1 proved similar to that of the other derivatives. MM2 calculations predicted a preferred gauche arrangement of the side chain for 1 and its analogues; such an arrangement was also observed in the solid state of muscarone picrate. Thus, the antiperiplanar arrangement reported for crystalline muscarone iodide appears to be due to crystallographic packing forces. As a consequence, the rationalization of the pharmacological profile of 1 based on the antiperiplanar arrangement is now highly questionable. The lack of stereoselectivity of 4 can be attributed to the absence of a stereocenter at C-2 whereas, in our opinion, there are currently no sound explanations for the low values of eudismic ratios for the muscarone enantiomers.

3-Trans-cinnanyl-8-propionyl-3,8-diazabicyclo[3,2,1]octane 1 , its monocyclic analog 4-trans-cinnamyl-1-propionyl-cis-2,6-dimethylpiperazine 2 and their isomers having the nitrogen sustituents exchanged, 3 and 4 , have been submitted to conformational analysis by molecular mechanics and 1 H NMR spectroscopy. The results of molecular modeling indicate that, while the monocyclic compound 2 has a preferred conformation very similar to the corresponding bicyclic compound 1 , compound 4 is quite different with respect to 3 ; it is the only compound with equatorially oriented substituents on the carbon atoms of the hexacyclic ring. This feature could explain the low affinity of 4 towards μ receptors, as compared with the high affinity of 1 – 3 .

The synthesis of a carba-analogue corresponding to the trisaccharide repeating unit of Streptococcus pneumoniae type 19F capsular polysaccharide, where a residue of carba-L-rhamnose has been inserted into the natural trisaccharide in place of L-rhamnose, is described. The conformational properties of the analogue were investigated with the aid of molecular dynamics simulations and were strictly analogous to those of the natural compound. The biological activity of the carba-analogue was comparable to that of the corresponding natural repeating unit, thus suggesting that this compound, more stable to hydrolysis, is a good mimic of the natural structure.

The conformational behavior of methyl (2-acetamido-2-deoxy-alpha-d-mannopyranosyl)phosphate 1, and its analogues, methyl C-(2-acetamido-2-deoxy-alpha-d-mannopyranosyl)methanephosphonate 2 and methyl O-(2-acetamido-2-deoxy-5a-carba-alpha-d-mannopyranosyl)phosphate , where a methylene group replaces, respectively, the anomeric and the pyranose oxygen atom, was investigated at the B3LYP/6-311+G(d,p) level [6-311+G(2df,p) for the phosphorus atom]. The energy of the optimized structures was recalculated using the continuum solvent model C-PCM choosing water as the solvent. The compounds exhibited several populated conformations, but they all showed a marked preference for the (4)C(1) geometry of the pyranose ring; this preference was almost complete for 1, very large for the phosphono analogue 2, and large for the carba analogue 3. To give experimental support to these results, compounds 2 and 3 were synthesized and characterized by NMR spectroscopy. The comparison of the theoretical and experimental vicinal coupling constants confirmed the marked preference for the (4)C(1) geometry in the case of 2 and suggested that the same holds true for compound 3.

(Chemical Equation Presented) Violet smelling ionones 1-3, occurring in the headspace of different flowers, are well-known perfumery raw materials. With the goal to recognize the still ill-defined spatial arrangement of structural features relevant to the binding of ionones to olfactory G-protein coupled receptors, through B3LYP/6-31G(d) modeling studies we identified bicyclic compounds 7-9 as conformationally constrained 13-alkyl-substituted analogues of monocyclic α- and γ-ionones. They were thus synthesized to evaluate the olfactory properties. The enantioselective syntheses of 7-9 entailed two common key steps: (i) a Diels-Alder reaction to construct the octalinic core and (ii) a Julia-Lythgoe olefination to install the α,β-enone side chain. The odor thresholds of synthetic 7 and 9 were significantly lower than the corresponding parent ionones, and 9 showed the lowest threshold value among violet-smelling odorants examined so far. Modeling studies suggested a nearly identical spatial orientation of key hydrophobic and polar moieties of compounds 1, 3, and 4-9. Presumably, interaction of these moieties with ionone olfactory receptors (ORs) triggers a similar receptor code that is ultimately interpreted by the human brain as a pleasant woody-violet smell. These results open the way to studies aimed at identifying and modeling complementary binding sites on α-helical domains of ionone receptor proteins.

Rearrangement of the tricarbonyl(cycloheptatriene)iron derivative 1 to 2 and 3 took place very readily in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) at room temperature. This finding is in striking contrast to the stability of 1 in MeOH under otherwise similar conditions. The isomerization processes which give rise to an equilibrium among 1, 2 and 3 must involve zwitterionic intermediates of the type 4, whose formation, consequently, is highly favored by HFIP. Heating 9 in HFIP brought about its rearrangement to 15. We suggest that formation of the zwitterionic intermediate 12 triggers a rearrangement of the carbocyclic moiety which can take place as a result of the high polarity and low nucleophilicity of HFIP. The rearrangement 9 → 15 could not be achieved by using other polar solvents such as methanol or nitromethane. This observation once again demonstrates how suitable HFIP is as a medium for isomerizations via zwitterionic intermediates. The role of traces of free acid, present even in purified HFIP, is discussed.

The structures of saponaceolides B, C and D, new C-30 terpenoids from Tricholoma saponaceum, have been established, including their absolute configuration. High cytotoxic activity was detected for saponaceolides B and C.

Methyl 6-O-butyryl-α-D- and -L-galactopyranoside and methyl 6-O-butyryl-α-D- and -L-mannopyranoside, which present three contiguous secondary hydroxy groups in different orientations, have been acylated using three hydrolytic enzymes. Porcine pancreatic, Candida cylindracea, and Pseudomonas fluorescens lipases in organic solvents. Some generalization of the obtained results is discussed. Methyl 6-O-butyryl-α-D- and -L-galactopyranoside and methyl 6-O-butyryl-α-D- and -L-mannopyranoside, which present three contiguous secondary hydroxy groups in different orientations, have been acylated using three hydrolytic enzymes. Porcine pancreatic, Candida cylindracea, and Pseudomonas fluorescens lipases in organic solvents. Some generalization of the obtained results is discussed.

Irradiation of 1,4-dicyanonaphthalene (DCN) and benzyl methyl ether gives the two diastereoisomeric 1-substituted 1,2-dihydronaphthalenes. A stereochemical assignment for these products, and related diastereoisomers pairs is proposed. The reaction occurs via the free radical ions and the low quantum efficiency is due to the slow deprotonation of the radical cation, with only moderate salt effect. In accordance with this scheme, the reaction with benzyl l-menthyl ether gives a low enantiomeric eccess.

Unsubstituted phenylpyridazinones 1a and 2a and their tricyclic analogues indenopyridazinone 3a, benzocinnolinone 4a, and benzocycloheptapyridazinone 5a were submitted to conformational analysis with Allinger's MM2(85) program in order to better define the relationship between the cardiovascular properties of some derivatives and their preferred conformations. Structures 1-4, giving rise to highly active compounds, were found to exist in a conformation showing a near-planar arrangement of the phenyl and the pyridazinone ring. On the contrary, 5, whose derivatives were inactive, shows two significantly populated conformations both markedly deviated from planarity. 1H NMR analysis of the tricyclic systems 3-5 was in full agreement with the molecular mechanics calculations.

Etude d'acylation regioselective par des lipases de Candida cylindracea, Pseudomonas fluorescens provenant du pancreas de porc, des methyl α-L- et α-D-rhamnopyranosides, les methyl α-L- et α-D-fucopyranosides. Bien que les sucres D donnent essentiellmenet le 2-butyrate, les enantiomeres L montrent une regioselectivite differente. Cependant, la reactivite du groupement OH en 4 peut devenir preferentielle dans la serie L en choisissant judicieusement l'enzyme

The 1,3-dipolar cycloaddition of diazomethane, diazoethane, phenyldiazomethane, and 2-diazopropane with several cyclobutenes, with open and cyclic cis 3,4-disubstitution, has been investigated. The cycloaddition proceeds in good yield to give syn and/or anti adducts. The structure of the adducts was established by spectroscopic data. The reactions of diazomethane cover the complete range of facial selectivity from 100% syn diastereoselectivity (e.g., with bis(mesyloxy)cyclobutene) to 100% anti diastereoselectivity (e.g., with bicyclo [3.2.0] hept-6-ene) through mixtures of various syn:anti ratios [e.g., syn:anti=60:40 with bis(methoxycarbonyl)cyclobutene]

The conformational space of cuanzine was explored by employing MM2 force field for energy calculations and minimization. Location of the global minimum on the potential energy surface furnished a geometry which resembles the literature reported X-ray conformation of vincamine

INTRODUCTION Regioselective esterification of sugars may represent a valuable tool for providing useful intermediates in the synthesis of more complex structures. A relatively easy solution to the problem can be found when discrimination between a primary vs secondary hydroxyl function is needed, but it seems to be quite unsolvable in a single chemical step when two or more secondary alcoholic groups are competing in the reaction with a given acylating reagent. Hydrolytic enzymes were found to be catalysts of great utility in this respect. Several cases are described in the literature concerning the selective deprotection of acylated sugars in aqueous media,1 and the esterification of free sugars or their alkyl glycosides in non-polar organic solvents1a,2 which first involve the primary alcohol function.3 Enzyme-catalyzed acylation in organic media at secondary alcohol positions was also studied4 in the case of 6-O-butyryl-glucose, -mannose, and -galactose and the 2-OH and/or 3-OH esterifications were sho...

The Claisen rearrangement of six homogeneous series of (R,S) or (R,R) 1,4-diaryl-6-isopropenyl-6-methyl-5,6-dihydro-4H-pyran[2,3-c]pyrazoles ( 1–6 ) to give 1,2-dimethyl-5-arylcyclohexene-4-spiro-4′(1′-aryl-5'-pyrazolones) ( 7–12 ) was kinetically investigated at 125°C in C 6 D 6 . When the substituents are on the 1-aryl group ( 1,2 ) the rate Increased with increases in the electron-attracting character of the substituent. When the substituents are on the 4-aryl group and the configuration is (R,S) ( 3,5 ), the rate decreased with increases in the electron-attracting character of the substituent. If the configuration is (R,R) ( 4,6 ) a lower, opposite, effect was observed. All kinetic data correlate linearly with the ρ of the substituents. These results can be rationalized by assuming for the Claisen rearrangement a transition state having significant dipolar character, with a partial negative charge developed on the oxygenated fragment.

The solvent effect of Diels-Alder (D.A.) reactions with heterodienophiles was measured in several solvents. The rate of the reaction between 2,3-dimethylbutadiene (DMB) and diethylazodicarboxylate increases with the increases in the Acceptor Number of the solvent which behaves as an electrophile. The rate of the reaction between DMB and p. bromonitrosobenzene shows a small solvent effect which correlates with the cohesive pressure (δH2) of the solvent. The rate of the reactions between DMB and tetrachloro- or tetrabromo-o.benzoquinones give an inverse linear relationship with Dπ basicity parameters, thus rate decreases with increases in the nucleophilic character of the solvent..p]These monoparametric correlations (alternatively obtained with electrophilic, nucleophilic or cohesive pressure parameters of the solvent) rationalize the solvent effect of D.A. reactions reported in the literature, which fit one of the above reported three classes. The same result is obtained if the Kamlet-Taft multiparametric equation is applied to the same set of reactions. The main contribution remains that outlined with the monoparametric approach and some secondary effects or some borderline cases are usefully focussed

A series of exceptionally potent agonists at neuronal nicotinic acetylcholine receptors (nAChRs) has been investigated. Several N-(3-pyridinyl) derivatives of bridged bicyclic diamines exhibit double-digit-picomolar binding affinities for the alpha 4 beta 2 subtype, placing them with epibatidine among the most potent nAChR ligands described to date. Structure-activity studies have revealed that substitutions, particularly hydrophilic groups in the pyridine 5-position, differentially modulate the agonist activity at ganglionic vs central nAChR subtypes, so that improved subtype selectivity can be demonstrated in vitro. Analgesic efficacy has been achieved across a broad range of pain states, including rodent models of acute thermal nociception, persistent pain, and neuropathic allodynia. Unfortunately, the hydrophilic pyridine substituents that were shown to enhance agonist selectivity for central nAChRs in vitro tend to limit CNS penetration in vivo, so that analgesic efficacy with an improved therapeutic window was not realized with those compounds.

DFT calculations at the B3LYP/6-311+G(d,p) level for the C, H, and O atoms and at the 6-311+G(2df,p) level for the S atom were used to study the hetero-Diels–Alder reactions between several α-oxothiones and ethylene or methyl vinyl ether (MVE). All the transition states and the intermediates along the reaction pathways, as well as the reaction products, were located. The reactions with ethylene are all concerted though asynchronous whereas in the reactions with MVE the electron-releasing character of the methoxy substituent lowers the energy barriers and enhances the asynchronicity and the charge transfer process to such an extent that the reaction may become unconcerted and exhibit a two-step mechanism with a zwitterionic intermediate derived from nucleophilic attack of electron-rich MVE to the sulfur atom of the strongly electrophilically activated α-oxothiones. The reactions are also favored by the conjugation of the newly formed C=C bond. Moreover, the geometric features of the diene exert a nonnegligible role, as dienes that are planar or almost planar in their ground state show a lower energy barrier. Thus, both geometric and electronic features of the dienes as well as of the dienophiles play a significant role in the easiness of the reactions and in their mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The conformational preferences of a group of 13-ethylsteroids and related estranes have been determined through theoretical calculations at the B3LYP/6-31G * level in order to ascertain differences and similarities in the conformational behavior which might, in principle, influence the activity. Attention was focussed on two geometrical features usually related to the progestational activity of this class of compounds, namely, the inversion of the A ring and the orientation of the 13-ethyl group. The present calculations show that the absence of the C10 methyl group, like in levonorgestrel, 3-ketodesogesterel, and gestodene, makes the inversion of the A ring easier than in norethisterone and ethisterone even if in any case the 1α,2β-half-chair conformation remains preferred. The preference of the ethyl group for the trans orientation is maintained by all the 13-ethylprogestogens though in gestodene also the g + gauche conformation is significantly populated. This preference was experimentally supported through a high field NMR spectroscopy study of the ethylsteroids.

A series of novel Acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors 8a-f was synthesized; the substances were characterized by the presence of a 2,5-dimethylpyrazin-3-yl moiety at one end and a 3-heptylamino-5- phenylpyridazine system at the other one, linked through linear alkyl spacers of different length. The new derivatives were designed based on the hypothesis that the 3-amino-5-phenylpyridazine moiety could mimic the aryl substituted urea, which was present in a number of ACAT inhibitors previously described. The choice of the 2,5-dimethylpyrazin-3-yl substituent was supported by a preliminary investigation, which indicated that this moiety is the most powerful in conferring ACAT inhibitory properties to the new series. The pharmacological results proved the idea to be sound. Finally, compounds 9a-c, lacking the phenylpyridazine moiety were prepared and tested to further strengthen our hypothesis.

A series of N-(2,4-difluorophenyl)-N′-heptyl-N′-{4- [(substituted)-pyridazin-3-yl)thio]pentyl}urea derivatives having a phenyl ring at positions 5 and/or at position 6 of the heterocycle, as well as the corresponding sulfones, were synthesized. Their inhibitory activity against acyl-CoA:cholesterol acyltransferase (ACAT) was tested on the enzyme prepared from rat liver microsomes. Theoretical studies were performed to correlate their activity to their structural features.

The three potential energy surfaces of the trans-trans, cis-trans, and cis-cis divinyltetramethylene diradicals have been located with DFT calculations at the BPW91/6-311+G** levels. The three surfaces account well for the experimental results reported for the thermolysis of optically active trans-1,2-divinylcyclobutane and optically active and deuterated 4-vinylcyclohexene. The surfaces account also for the outcome of the dimerization of butadiene and the thermolysis of cis,cis-1,5-cyclooctadiene. The three diradical intermediates are connected to the cyclization and dissociation products through conformations that are explored fully here.

6-Dehydroretroprogesterone (dydrogesterone) and three other natural or synthetic progestins (progesterone, retroprogesterone, and 6-dehydroprogesterone) were submitted to a conformational study through theoretical calculations at the B3LYP/6-31G * level and high field NMR spectroscopy. The study allows to define the role of the two structural features which differentiate these steroids, i.e., the C9 and C10 configuration and the C6–C7 unsaturation. The combined effects of the conformational preference of A ring, determined by the configuration at C9 and C10, and the enhanced rigidity due to the C6–C7 double bond, could account both for the higher activity and selectivity of dydrogesterone with respect to the other three steroids.

In an effort to improve diazabicycloalkane-based opioid receptor ligands, N -3(6)-arylpropenyl- N -6(3)-propionyl-3,6-diazabicyclo[3.1.1]heptanes ( 3A , Ba – i ) were synthesized and their affinity and selectivity towards μ-, δ- and κ-receptors were evaluated. The results of the current study revealed a number of compounds ( 3Bb , 3Bg and 3Bh ) having a high affinity for μ ( K i at μ-receptors ranging from 2.7 to 7.9 nM) versus δ ( K i at δ-receptors >2000 nM) and versus κ ( K i at κ-receptors >5000 nM) receptors. Molecular modelling carried out on the pair 3Aa/3Ba and on the 3Bh was consistent with the hypothesis that the two series of compounds 3A and 3B interact with the μ-receptor in very different ways.

A series of analogues of 8-chloro-1-(2',4'-dichlorophenyl)-N-piperidin-1-yl-1,4,5,6-tetrahydrobenzo[6,7]cyclohepta[1,2-c]pyrazole-3-carboxamide 4a (NESS 0327) (Ruiu, S.; Pinna, G. A.; Marchese, G.; Mussinu, J. M.; Saba, P.; Tambaro, S.; Casti, P.; Vargiu, R.; Pani, L. Synthesis and Characterization of NESS 0327: A Novel Putative Antagonist of CB1 Cannabinoid Receptor. J. Pharmacol. Exp. Ther. 2003, 306, 363-370) was synthesized and evaluated for their affinity to cannabinoid receptors. Depending on the chemical modification of the lead structure that was chosen, compounds 4b, 4c, 4i, 4l, and 4m still proved to be potent binders of the CB1 receptor. Moreover, several analogues (4c, 4d, 4e, and 4m) demonstrated superior CB2 receptor binding affinities compared to the parent ligand. Compounds 4b, 4c, 4i, and 4l displayed the most promising pharmacological profiles, having the highest selectivity for CB1 receptors with Ki(CB2) to Ki(CB1) ratios of 11,250, 2000, 3330 and 4625, respectively. Compound 4c increased the intestinal propulsion in mice and antagonized the effect induced by the CB1 receptor agonist WIN 55,212-2. Finally, molecular modeling studies were carried out on a set of tricyclic pyrazoles (2a-4a) and on rimonabant 1 (SR141716A), indicating that high CB1 receptors affinities were consistent for the tricyclic derivatives, both with a nonplanar geometry of the tricyclic cores and with a precise orientation of the substituent (chlorine) on this ring system.

The conformational behavior of methyl(2-O-methyl-alpha-L-rhamnopyranosyl)phosphate, together with a group of potentially more stable analogues, was investigated through a DFT approach at the B3LYP/6-31G(d) level; the energy of all the optimized structures was recalculated using a continuum solvent model, C-PCM, choosing water as the solvent. The compounds exhibited several, sometimes tenths of populated conformations so that the overall properties of flexibility and mobility were evaluated. The analogue in which the pyranose oxygen atom is replaced by a methylene group emerges as the best candidate as a mimic of the reference 1-phosphate, in spite of the fact that it lacks the anomeric and exo-anomeric effects. The other analogues result poorer mimics because of a conformational equilibrium at the pyranose ring or of an excessive rigidity of the aglycone moiety.

A new series of pyridazine derivatives, structurally related to the previously reported ACAT inhibitors 3-(cyclo)alkylamino-5, 6-diphenyl-pyridazines, were synthesized and tested for their inhibitory properties. Substitution of the 3-alkylamino chain with a phenylamino group maintains activity. In contrast, the presence of either substituents on the phenylamino group or aliphatic rings having more or less than six carbon atoms lowers it.

3,8-Diazabicyclo[3.2.1]octane (1), 2,5-diazabicyclo[2.2.1]heptane (2), piperazine (3), and homopiperazine (4) derivatives, substituted at one nitrogen atom with the 6-chloro-3-pyridazinyl group while the other nitrogen atom was either unsubstituted or mono- or dimethylated, were synthesized and tested for their affinity toward the neuronal nicotinic acetylcholine receptors (nAChRs). All of the compounds had K(i) values in the nanomolar range. A molecular modeling study allowed location of their preferred conformations, the energies of which were recalculated in water with a continuum solvent model. Some of the compounds showed, in their populated conformations, only pharmacophoric distances longer than the values taken into consideration by the Sheridan model for nAChRs receptors. Thus, this SAR study gives support to the hypothesis that these longer distances are still compatible with affinity for alpha4beta2 receptors in the nanomolar range.

Nine new synthetic compounds, structurally related to the most active glycoglycerolipid analogues carrying a hexanoyl chain, were tested for their anti-tumor-promoting activity using a short-term in vitro assay for Epstein–Barr virus (EBV) activation. All these compounds, in which the ester function is replaced by different metabolically more stable groups, were almost as active as their ester reference compounds in inhibiting the EBV activation promoted by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Two of these, devoid of any functionality on the lipophilic chain, when tested in an in vivo two-stage carcinogenesis test, exhibited marked inhibitory effects on mouse skin tumor promotion.

The stereospecific endo dimerization of cyclopentadiene takes place through an asynchronous and symmetrical bispericyclic transition structure, which shows a merging of the 4+2 and 2+4 cycloaddition paths. The shape of the transition structure testifies to the presence of attractive Salem/Houk secondary orbital interactions assisting the endo approach.

The structure of 13-ethyl-11-methylene-18,19-dinor-17alpha-pregn-4-en-20-yn-16beta,17-diol (3, 16beta-OH desogestrel), a by-product obtained in the last step of the synthesis of desogestrel (1) by reaction of monolithium acetylide-ethylenediamine complex with 13beta-ethyl-11-methylenegon-4-en-17-one (2), is here reported. The structural assignments were supported by NMR 1H-, 13C-, 1H-1H COSY, 1H-13C HSQC, COLOC) and mass spectroscopy, and the configuration at the C-16 and C-17 stereocentres was established by X-ray crystallography. When the same 17-ketoderivative 2 was treated with a non-alkylating base, such as potassium tert-butoxide, instead of the expected 16-hydroxylated ketone, a dimeric product, 13beta-ethyl-16-[2'-(des-D-13"-carboxy-13"beta-ethyl-11"-methylenegon-4"-en-14"-yl)-ethyliden]-11-methylenegon-4-en-17-one (4), was isolated in good yield; it was characterized by NMR, mass, ultraviolet spectroscopy, and chemical transformations. Compounds 3 and 4 originate from the high reactivity of the 16-methylenic position of the 17-keto substrate (2) toward molecular oxygen under basic conditions.

Glycoglycerolipid analogues, characterized by a glycerol aglicone β-linked in position 2 to a glucose or galactose residue, and by a lipophilic C 6 acyl chain on the glycerol unit, significantly inhibit proliferation of activated T cells. The inhibitory activity displayed by such synthetic compounds is comparable to the immunosuppressive properties shown by the natural glycolipids simplexides, to which they are structurally related. Vice versa, when the acyl chain is located on the sugar unit, no immunomodulating activity is observed, suggesting a strict relationship between the activity and the location of the acyl chain.

Anew sequence, which encoded a novel G protein-coupled receptor, was disclosed by two different groups, using the nucleic acid probes based on the delta opioid receptor, first cloned in 1992. The new receptor, which Meunier called opioid-receptor-like 1 (ORL-1), was shown to share high homology with the opioid receptors and therefore thought to be a potential target for new analgesics. In this respect, the present review reports on the literature referring to ORL-1, to its natural ligand (nociceptin or orphanin FQ) and to several synthetic analogues recently described, both as agonists or antagonists at the receptor.

Four 1-oxo-cycloalkan-2-ylideneacetic acids, differing in the size of the aliphatic ring and in the nature of the condensed unsaturated cycle, exhibit different reactivities towards hydrazine, leading in only one case to the desired tryciclic pyridazinone. The observed differences in behaviour cannot be ascribed to different configurations at the exocyclic double bond of the four acids: 1H NMR experiments, combined with UV photolysis, have shown that all compounds have been prepared in the E form and are stable in the absence of light and catalysts. The photochemically obtained Z isomers show an increasing tendency to form tricyclic lactones with increasing size of the aliphatic ring. A theoretical structural analysis of the E and Z isomers, the tricyclic lactones and some of the hypothetical intermediates of the reaction with hydrazine suggests the size of the aliphatic ring and the associated flexibility to be crucial in modulating the ability of these compounds to form tricyclic products.

Three series of monoacyl-2- O -β- d -galactosylglycerols bearing an acyl chain of varying length, from C 4 to C 10 , were studied due to their antitumor promoting effects on the activation of the Epstein–Barr virus early antigen (EBV-EA), such activation being induced by the tumor promoter 12- O -tetradecanoylphorbol-13-acetate (TPA). This study indicates that it is more the length of the acyl chain that is important for the activity, six carbon atoms resulting in maximum effect, rather than the position of the ester function and the nature of the sugar (galactose or glucose).

A series of 3,8-diazabicyclo[3.2.1]octanes substituted either at the 3 position (compounds 1) or at the 8 position (compounds 2) by a chlorinated heteroaryl ring were synthesized, as potential analogues of the potent natural analgesic epibatidine. When tested in the hot plate assay, the majority of the compounds showed significant effects, the most interesting being the 3-(6-chloro-3-pyridazinyl)-3,8-diazabicyclo[3.2.1]octane (1a). At a subcutaneous dose of 1 mg/kg, 1a induced a significant increase in the pain threshold, its action lasting for about 45 min. 1a also demonstrated good protection at a dose of 5 mg/kg in the mouse abdominal constriction test, while at 20 mg/kg it completely prevented the constrictions in the animals. Administration of naloxone (1 mg/kg i.p.) did not antagonize its antinociception while mecamylamine (2 mg/kg i.p.) did, thus suggesting the involvement of the nicotinic system in its action. Binding studies confirmed high affinity for the alpha 4 beta 2 nAChR subtype (Ki = 4.1 +/- 0.21 nM). nAChR functional activity studies on three different cell lines showed that 1a was devoid of any activity at the neuromuscular junction. Finally, due to the analogy in their pharmacological profile with that of epibatidine, compounds were compared from a structural and conformational point of view through theoretical calculations and high-field 1H NMR spectroscopy. Results indicate that all of them present one conformation similar to that of epibatidine.

In a screening for cancer chemopreventing agents several glycosylglycerols were found to be active. In order to optimize the anti-tumor activity of this class of compounds, a series of 1-O-acyl-2-O-beta-D-glucopyranosyl-sn-glycerols differing in the acyl chain length, which varied from C4 to C18, were examined for their in vitro anti-tumor promoting effects on Epstein-Barr virus early antigen (EBV-BA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Among the compounds tested, the monohexanoyl derivative was the most active and, noteworthy, the most potent compound of the glycosylglycerol series hitherto known.

Through a cell-based biological screening, the benzocinnolinone derivative (±)-2c was identified as a promising STAT3 inhibitor. Since SAR studies on a series of compounds structurally related to (±)-2c (1c, 2a-p, 3c, 4c, 6) showed that the latter had the most significant inhibitory activity, we investigated in depth its essential structural features. In particular, enantiomeric separation was performed, and the absolute configuration of the stereoisomers was assigned by theoretical and crystallographic studies. The biological evaluation highlighted that (S)-(-)-2c is twice as potent as (R)-(+)-2c.

Signal Transducer and Activator of Transcription 3 (STAT3) is a latent cytoplasmic protein overexpressed in various cancer cell lines. STAT3 participates in oncogenesis by stimulating cell proliferation and preventing apoptosis and it has been proven as a suitable target for anticancer therapy. In order to identify direct STAT3 inhibitors, we performed a binding assay on several previously synthesized 1,2,5-oxadiazole derivatives. Among them, compound MD77, N-[4-(4-chlorophenyl)-1,2,5-oxadiazol-3-yl]-4-(trifluoromethyl) benzamide, showed a good ability to bind the STAT3-SH2 domain in a dose-dependent manner (IC50 = 17.7 μM). Computational studies were carried out to investigate its binding mode. Moreover, compound MD77 showed a significant anti-proliferative activity versus several tumor cell lines. On these bases, compound MD77 was selected as a lead for the future development of direct STAT3 inhibitors.

Avidin, a basic tetrameric glycoprotein, isolated from hen egg-white, binds up to four molecules of biotin with exceptionally high affinity. The presence of tryptophanyl residues in the active site pointed out the opportunity of correlating the protein fluorescence with biotin binding. We have performed both steady state and dynamic fluorescence experiments using biotin or biotin-derived molecules (biotinamine, diaminobiotin and iminobiotin) as ligands. The fluorescence decay data can only be fitted by two continuous distributions of lifetimes which may reflect the presence of static or dynamic microheterogeneity in the environment of the tryptophan residues. We observed that the binding of biotin, biotinamine and iminobiotin reduces the widths of both distributions to discrete lifetimes thus indicating a more homogenous environment for the emitting tryptophan residues. Instead, the binding of diaminobiotin, which lacks the imidazolone ring, affects one lifetime distribution only. The binding of biotin also affects the rotational correlation time of avidin, which becomes shorter, suggesting a more compact structure of the ligated protein. The utility of analyzing the fluorescence in terms of distributions appears to be further warranted.

STAT3 (Signal Transducer and Activator of Transcription 3) is a transcription factor constitutively activated by aberrant upstream tyrosine kinase activities in a broad spectrum of human solid and blood tumors, thus suggesting that its inhibition could represent an interesting molecular target for cancer therapy. With the aim to disclose novel scaffolds for compounds active on STAT3 the potential of the 1,2,5-oxadiazole ring was explored and several new compounds substituted at positions 3 and 4 of the heterocycle were synthesized. When tested in a dual-luciferase assay, using HCT-116 cells, some compounds showed a significant inhibition value towards STAT3. So, to give support to the biological results, modeling and crystallographic studies of representative terms of the new series were performed.