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a ) a Phytochemical investigation of the aerial parts of Gymnema sylvestre led to the isolation of two known oleanane-type triterpenes, 1 and 3, five new acylated derivatives, 2, 4, and 5 - 7, and a new lupane- type triterpene, 8. The structures and relative configurations of these compounds were elucidated by spectroscopic analyses, including 1D- and 2D-NMR spectroscopy and mass spectrometry, and by the comparison of their NMR data with those of related compounds. Introduction. - Gymnema sylvestre (Asclepiadaceae), a vulnerable species, is a slow-growing, perennial woody climber in tropical and subtropical regions (1). It is a potent antidiabetic plant and used in folk, ayurvedic, and homeopathic systems of medicine (2 - 5). It is also used in the treatment of asthma, eye complaints, inflammations, family planning, and snake bite (6 - 9). In addition, it possesses antimicrobial, antihypercholesterolemic (10), hepatoprotective (11), and sweet-sup- pressing activities (12). It also acts as feeding deterrents to caterpillar, Prodenia eridania (13), prevents dental caries caused by Streptococcus mutans (14), and it is used in skin cosmetics (15). The various reports on its multiple uses attracted attention for utilization of the plant for gynmemic acid (active principle). From the organic extract of G. sylvestre, we had isolated oleanane and lupane triterpenes (16). In the continuing the investigation of G. sylvestre, we have isolated two known oleanane-type triterpenes, 1 and 3, one obtained for synthesis, 2, four new acylated derivatives, 4 - 7, and a new lupane-type triterpene, 8. Results and Discussion. - Compound 1 was identified as (3b,16b)-olean-12-ene- 3,16,23,28-tetrol by comparison of its spectral data with those in the literature (17). Compound 2 had the molecular formula C38H58O8 on the basis of the quasi- molecular-ion peak at m/z 643.4204 ((M þ H) þ ) in the HR-ESI-MS spectrum and 13 C-NMR data. The 1 H-NMR spectra (Table 1) revealed the presence of two O-bearing CH and two O-bearing CH2 groups assigned by a HSQC experiment. The high chemical-shift values and the presence of four singlets, at d(H) 2.00 and 2.01, and 2.03 and 2.05 indicate that the carbinol functions are acetylated. The configurations of the O-bearing C-atoms have been deduced from a NOESY experiment, where the H-atom HC(3) showed a NOE effect with the H-atoms of CH2(23), and H-atoms of Me(24)

An improvement to our solid phase strategy to generate pharmacologically interesting molecule libraries is proposed here. The synthesis of newo-chlorophenol-functionalised solid supports with very high loading (0.18–0.22 meq/g for control pore glass (CPG) and 0.25–0.50 meq/g for TG) is reported. To test the efficiency of these supports, we prepared nucleotide and oligonucleotide models, and their coupling yields and the purity of the crude detached materials were comparable to previously available results. These supports allow the facile and high-yield preparation of highly pure phosphodiester and phosphoramidate monoester nucleosides, conjugated oligonucleotides, and other yet unexplored classes of phosphodiester and phosphoramidate molecules.

"Chemically modified siRNAs were synthesized to enhance the corresponding silencing activities. The introduced modifications endowed siRNAs with high silencing effect, long RNAi persistence and better serum resistance. The-oretical data allowed to correlate the observed siRNAs interfering performance with the peculiar interactions with PAZ." Chemically modified siRNAs were synthesized to enhance the corresponding silencing activities. The introduced modifications endowed siRNAs with high silencing effect, long RNAi persistence, and better serum resistance. Theoretical data allowed us to correlate the observed siRNAs interfering performance with the peculiar interactions with PAZ. © 2012 American Chemical Society.

Silybin is the major flavonolignan of silymarin and it displays a plethora of biological effects, generally ascribed to its antioxidant properties. Herein we shall describe an efficient synthetic strategy to obtain a variety of new and more water-soluble silybin and 2,3-dehydrosilybin (DHS) derivatives in which the 23-hydroxyl group was converted to a sulfate, phosphodiester, or amine group, using a solution-phase approach. Furthermore a new and efficient method for the preparation of DHS from silybin was developed and optimised. The antioxidant properties of the new compounds were evaluated in a cellular model in vivo and they displayed an antioxidant activity comparable to or higher than silybin and DHS, being able to prevent H 2 O 2 -induced generation of intracellular reactive oxygen species (ROS). Most of the derivatives also displayed a better hydrophilicity while retaining the biological activities of silybin and they might broaden the in vivo applications of this class of natural compounds.

A versatile approach to develop libraries of diverse 5',3'-bis-conjugated oligonucleotides (ODNs) is here described. The usage of ad hoc derivatized solid supports, to which the first nucleoside unit is attached through a phosphate linkage, opens easy synthetic access to a large variety of hybrid bis-conjugated oligomers. The G-quadruplex forming d((5')TGGGAG(3')) sequence, as a potential anti-HIV agent, has been here used as a model system.

Patulin is a toxic secondary metabolite of a number of fungal species belonging to the genera Penicillum and Aspergillus. It has been mainly isolated from apples and apple products contaminated with the common storage-rot fungus of apples, Penicillum expansum, but it has also been extracted from rotten fruits, moldy feeds, and stored cheese. Human exposure to patulin can lead to serious health problems, and according to a long-term investigation in rats, the World Health Organization has set a tolerable weekly intake of 7 ppb body weight. The content of patulin in foods has been restricted to 50 ppb in many countries. Conventional analytical detection methods involve chromatographic analyses, such as HPLC, GC, and, more recently, techniques such as LC/MS and GC/MS. However, extensive protocols of sample cleanup are required prior to the analysis, and to accomplish it, expensive analytical instrumentation is necessary. An immunochemical analytical method, based on highly specific antigen-antibody interactions, would be desirable, offering several advantages compared to conventional techniques, i.e., low cost per sample, high selectivity, high sensitivity, and high throughput. In this paper, the synthesis of two new derivatives of patulin is described, along with their conjugation to the bovine serum albumin for the production of polyclonal antibodies. Finally, a fluorescence competitive immunoassay was developed for the on-line detection of patulin.

A number of 5'-and 3'-glycoconjugates of the oligonucleotide (5')d(TGGGAG)(3') have been synthesized, exploiting fully automated, online phosphoramidite-based solid phase strategy, as potential anti-HIV-1 agents. The thermodynamic stability of the resulting quadruplexes has been investigated by thermal denaturation studies, via a detailed CD Q1 analysis.

A new and versatile on-line automated solid-phase approach to obtain cyclic PNA (I and III) and cyclic PNA-DNA chimeras (II) in highly pure form has been developed. Starting from a Tentagel matrix functionalized with a 3-chloro-4-hydroxyphenylacetic linker, the synthesis of representative, new cyclic molecules by standard peptide and phosphoramidite-based chemistry has been achieved. © 2006 American Chemical Society.

2-(Phenylthio)ethyl is here proposed for temporary masking the thymine residue in the synthesis of sugar modified thymidine derivatives. This protection has been devised as a 'two-stage' system. The 2-(phenylthio)ethyl residue can be easily and regiospecifically inserted at the N3-position of the pyrimidine by a Mitsunobu reaction with 2-(phenylthio)ethanol and is perfectly stable also to strongly basic conditions. This allowed us to selectively achieve O-alkylation of the ribose moieties in satisfactory yields, avoiding undesired base alkylations. After oxidation of the thioether to sulfone, the thymine protecting group can be totally removed, by a β-elimination mechanism, upon the same basic treatment required for the final deprotection and detachment of oligonucleotides from the support in solid-phase synthesis protocols. © Georg Thieme Verlag Stuttgart.

[reaction: see text] An easy and efficient solid-phase strategy to obtain 5'- and 3'-oligonucleotide conjugates in highly pure form has been developed. Ad hoc derivatized solid supports, to which the first nucleoside unit can be attached through a phosphate linkage, have been exploited both in a pre- and post-DNA assembly conjugation approach. A number of 5'- or 3'- oligonucleotide conjugates, incorporating a variety of labels covalently linked through a phosphodiester or a phosphoramidate bond, have been synthesized and characterized.

The online solid-phase synthesis of oligonucleotides conjugated at the 3' end with [1-6]-linked oligosaccharide mimics having the O-glycosidic linkages replaced by amide bonds is here described. The assembly of the carbohydrate domain has been carried out by exploiting classical solid phase peptide synthetic protocols, starting from solid supports functionalized with 1-azido sugars, in association with suitably protected 1-azido uronic acids of glucose and lactose, chosen as model addition monomers. After the insertion of a flexible linker, elongation of the oligodeoxyribonucleotide (ODN) chain was performed by standard automated phosphoramidite protocols. 3'-Glycoconjugated 18-mers exhibited an increased enzymatic stability with respect to the same unmodified ODN sequence. UV thermal denaturation experiments showed that the presence of the oligosaccharide tail at the 3' end of the oligonucleotides did not negatively interfere with their duplex formation abilities.

An easy and efficient strategy to obtain libraries of 5′-phosphodiester and 5′-phosphoramidate monoester nucleoside analogues in a highly pure form has been developed, starting from a new nucleoside based solid support. The nucleoside scaffold has been anchored through a 5′-phosphodiester linkage to Tentagel® HL resin, functionalized with a 3-chloro-4-hydroxyphenylacetic linker. The solid phase synthesis of small libraries of 5′-phosphodiester and 5′-phosphoramidate monoester thymidine analogues is also reported.

New solid supports, linking protected pyrimidine and purine nucleoside derivatives through the nucleobase, have been prepared. The support, incorporating a suitable derivative of 2'-azido, 2'-deoxyuridine, allowed the simple and efficient solid-phase synthesis of ribose-modified nucleoside and nucleic acid analogues, particularly of aminoacyl derivatives of 2'-deoxy, 2'-amino-uridine, following methodologies well established in peptide and oligonucleotide chemistry.

Novel compound 1, as the first example of cyclic ADP-ribose analogs containing a pyrimidine residue, was synthesized by a chemical strategy employing a Mitsunobu reaction for the condensation of the glucosyl moiety on protected uridine, and a Matsuda procedure for the cyclization step.

A systematic study to evaluate the ability of 5′-DNA-3′-p-(N)-PNA-(C) chimeras to form triple helix structures has been undertaken. Preliminary results carried out on a 16-mer chimera with three PNA monomers at the 3′-end showed the formation of a stable DNA-PNA/DNA/DNA triplex, having similar conformational behaviour to a canonical DNA/DNA/DNA triplex.

An easy and efficient strategy to obtain new nucleoside based solid supports in which the nucleoside moieties have been anchored to the solid support through the nucleobase is here proposed. A simple and efficient solid-phase synthesis of 5' and 3'-derivatized uridine analogues has so been developed, following methodologies well established in organic chemistry.

Oligonucleotides conjugated at both 3′ and 5′-ends with glucose residues, 4,6-linked through a phosphodiester bridge, have been synthesized by sequential addition of a 6- O -DMT-glucose-4-phosphoramidite building block following a standard automated ODN assembly procedure. Two 3′,5′-bis-glycoconjugated 18-mers, designed for antisense experiments, have been prepared and their hybridization properties with a complementary DNA fragment evaluated by UV thermal analysis.

Oligonucleotides carrying a peptide nucleic acid (PNA) tail at the 3′-end have been efficiently prepared by an on-line automated synthetic protocol exploiting commercially available Bhoc/Fmoc PNA monomers for the assembly of the PNA tract, followed by a deprotection/reprotection of the base protecting groups. The syntheses of the ODN domain in the chimeras have then been performed by standard methods. The hybridization properties of the synthesized chimeras with complementary DNA fragments have been investigated by thermal denaturation experiments. © 2001 Elsevier Science Ltd. All rights reserved.

Gluco- and ribosylation of the bases of sugar protected inosine and uridine were investigated, obtaining only adducts with beta -configuration at thenew glycosidic carbon; stereospecific insertion of a sugar moiety at the 1-N of inosine was achieved either using a Mitsunobu approach (for ribosylation) or by direct coupling of 1-alpha -bromoglucose 13 with 2',3',5'-tri-O-acetylinosine for glucosylation. 1-(beta -D-glucosyl)-inosine, chosen as starting substrate for glucosylated analogs of cyclic IDP-ribose, was phosphorylated at the primary hydroxyls and tested in intramolecular pyrophosphatebond formation.

An improved protocol for the synthesis of oligonucleotides containing a 3′-3′ phosphodiester linkage, for use in an alternate strand triple-helix formation approach, is reported. Three 16-mers and one 24-mer have been efficiently synthesized and the corresponding triplexes have been analyzed by thermal denaturation experiments and CD spectroscopy.

A first solid phase approach to obtain monosubstituted CD conjugates to different labels has been developed. A new solid support has been designed to get a variety of C-6 monofunctionalized CDs (α, β, MeβCD and HPβCD) covalently linked through a phosphodiester bridge to different labels, in highly pure form and under very mild detachment conditions. © The Royal Society of Chemistry 2012.

In order to expand the repertoire of available oligosaccharide-oligonucleotide hybrids, the on-line solid phase synthesis of oligonucleotides conjugated at the 3′- and/or 5′-end with a preformed disaccharide unit has been performed. The key compound in the synthetic scheme described here is an appropriate phosphoramidite derivative of fully protected sucrose, used in association with a solid support functionalized with DMT-protected sucrose. The sucrose units at both ends of selected oligonucleotide sequences were shown to increase their chemical and enzymatic stability, while not interfering with duplex formation and with the ability of G-rich sequences to adopt a quadruplex structure.

The photophysical and photochemical properties of 5-benzyluracil and 5,6-benzyluracil, the latter produced by photocyclization of the former through irradiation with femtosecond UV laser pulses, are investigated both experimentally and theoretically. The absorption spectra of the two molecules are compared, and the principal electronic transitions involved are discussed, with particular emphasis on the perturbation induced on the two chromophore species (uracil and benzene) by their proximity. The photoproduct formation for different irradiation times was verified with high-performance liquid chromatography and nuclear magnetic resonance measurements. The steady-state fluorescence demonstrates that the fluorescence is a distinctive physical observable for detection and selective identification of 5- and 5,6-benzyluracil. The principal electronic decay paths of the two molecules, obtained through TDDFT calculations, explain the features observed in the emission spectra and the photoreactivity of 5-benzyluracil. The order of magnitude of the lifetime of the excited states is derived with steady-state fluorescence anisotropy measurements and rationalized with the help of the computational findings. Finally, the spectroscopic data collected are used to derive the photocyclization and fluorescence quantum yields. In obtaining a global picture of the photophysical and photochemical properties of the two molecules, our findings demonstrates that the use of 5-benzyluracil as a model system to study the proximity relations of a DNA base with a close-lying aromatic amino acid is valid at a local level since the main characteristics of the decay processes from the excited states of the uracil/thymine molecules remain almost unchanged in 5-benzyluracil, the main perturbation arising from the presence of the close-lying aromatic group.

Two new thymidine based polymeric supports, in which the nucleosides have been anchored through the thymine moiety to a β-hydroxy thioether functionalized resin via a Mitsunobu reaction, have been prepared. A simple and efficient solid-phase synthesis of 5′,3′-bis-derivatized thymidine analogues has so been developed, following methodologies well established in peptide and oligonucleotide chemistry and is here proposed for the preparation of a variety of different nucleoside conjugate products.

An easy and more efficient synthesis of oxanosine and 2′-deoxyoxanosine has been developed, a key step in the reported synthesis is a new photochemical transformation by UV irradiation of 1-hydroxy derivatives of inosine.

A simple and efficient bidirectional solid-phase synthe- sis, based on the use of a Tentagel solid support, functionaiized with a suitably protected 2-amino sugar residue, is proposed for the prep- aration ofa variety ofglycoconjugates, including glycopeptides and nucleo- glycopeptides. Since the biomedical potential of oligosaccharides and re- lated glycoconjugates has been well recognizedl-5 the de- velopment of effective methodologies for their rapid assembly is attracting current attention. Glycoconjugates are among the most functionally and structurally diverse molecules in nature and it is now well established that pro- tein- and lipid-bound saccharides play essential roles in many molecular processes impacting eukaryotic bioiogy and disease. The presence of a sugar moiety is believed to influence the transport of the drug through biological membranes as well as to increase its resistance to hydro- lytic enzymes. The synthesis and modification of oligosaccharide units and their coupling with appropriate lipids, phospholipids, oligonucleotides and proteins are essential to extend the knowledge on the molecular mode of action of glycocon- jugates and, furthermore, to get a further insight into their physiological activity. In this context the polymer sup- ported approach is particularly promising in principie. A iarge number of studies on the solid-phase synthesis of glycopeptides have been reported6'7 and since the polymer supported synthesis of peptides is a weli established pro- cess,8 the majority of progress in the synthesis of glyco- peptides has involved the linkage of the giycopeptide to the polymer support via the peptide moiety rather than via the carbohydrate moiety. Recentiy several papers have been reported in the literature dealing with the synthesis of giyco-oligonucleotide conjugates in which the sugar residue is either attached to the nucleotide base before the oligonucleotide assembiy,e or used as separate building block in an "on iine" solid phase strategy.i0-12

Ribosylation and glucosylation of the base residues of inosine and uridine have been efficiently achieved using Mitsunobu reaction, leading to the N-1 and 6-O-glycosylinosine and N-3-glycosyluridine derivatives, all with β configuration at the glycosidic carbon. The unprecedented 5-amino-1-(β-D-ribofuranosyl)imidazole-4-[N-(β-D-glucopyranosyl) carboxamide] has also been synthesised. © The Royal Society of Chemistry 1999.

Cyclic oligonucleotides and analogues (cONs) are highly specific ligands for DNA, RNA and proteins. cONs are described in several diagnostic and therapeutic applications, as well as in elucidating enzyme mechanisms and as lead structures for development of new drugs because of their unusual chemical and biological properties in comparison with linear counterparts. In numerous structural studies it has been shown that conformational constraints imposed by circularity cause unique topologies, which in some cases can result into peculiar ON nanostructures. The wide field of applications of cONs has called for the definition of easy and efficient strategies to produce such compounds. In this review, we will describe the enzymatic and chemical approaches reported for the synthesis of cONs with a particular focus on the chemical ones. We proceed following a chronological order from the earliest to the latest methods and improvements, describing at first the natural cyclic ONs and then modified linkages and cyclic analogues. © 2012 Bentham Science Publishers.

The first examples of direct glycosidation of the 5′-OH end of polypyrimidine oligonucleotides still attached to the CPG solid support are reported. A general re-elongation solid phase procedure has been developed to successfully isolate the target 5′-glycosyl derivatives. A 3′,5′-diglucosylated 16-mer oligonucleotide has also been obtained.

Silybin is the main component of silymarin with antioxidant, anti-inflammatory and cytoprotective actions. Our aim was to compare the effect of silybin used as single substance, silybin-phosphatidylcholine complex (SilPho), and derivatives of silybin (MannpSil, GalpSil, GlcpSil, LactpSil) on MKN28 and HepG2 cell viability and cell death, in vitro, after induction of oxidative stress.

We here describe the synthesis of a series of novel bicyclic ribonucleoside derivatives, with 18-crown-6 ether moieties attached via their ribose 2- and 3- positions, as first examples of crown ether ring-fused nucleosides, to be evaluated as antiviral and/or antitumoral agents.