The genome DNA is constantly exposed to endogenous and exogenous oxidative stresses. Damaged DNA can cause mutations, which may increase the risk of developing cancer, aging, and other diseases. Various oxidative stresses lead to G:C–T:A and G:C–C:G transversions, because guanine is highly susceptible to oxidative stress in the DNA, owing to the lowest oxidation potential among four nucleobases. One typical lesion product of guanine is 8-oxo-7,8-dihydroguanine (8oxoG), and DNA polymerases incorporate adenine but not guanine opposite 8oxoG lesions. More specifically, 8oxoG:A base pairs cause G:C–T:A transversions, and then the other oxidative guanine damages seem to cause G:C–C:G transversions. 2,5-diamino-4H-imidazol-4-one (Iz) and 2,2,4-triamino-5(2H)-oxazolone (Oz) are the oxidative guanine damages, which can pair with guanine, and several DNA polymerases incorporate guanine opposite these lesions in vitro. We previously reported that the calculated stabilization energy of Iz:G base pair is similar to that of C:G base pair and that of Oz:G base pair is planar and has two hydrogen bonds. Guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) are the oxidative products of 8oxoG. It was shown that Klenow fragment incorporated adenine and guanine opposite these lesions. Our previous study proposed Gh:G and Sp:G base pairs, however, the stabilization energy of these base pairs have not been calculated. Therefore, We estimated the stabilization energy of these base pairs by ab initio molecular orbital calculations.

Fluorescent cholic acid derivatives are used as well in biological investigations as in chemical. As nature products their derivatives can be used in research of hepatotoxicity, cell transport system and distribution of the drugs in organisms. Cholic acid-based fluorescent sensors are used to detection different organic and inorganic compounds such as drugs, toxins, amino acids and heavy metals. \'Fluorophore–spacer–receptor\' motif is an effective way of designing of plurality of chemosensors and has used in the last two decades. Coumarines containing electron donating groups are natural non-toxic compounds that have good fluorescent parameters. It is also known that rearrangement of imino-coumarines is the easy way to fluorescent coumarine derivatives. Hence, in present work fluorescent receptor precursors bearing coumarine fluorophore on C24 of cholic acid were designed and synthesized in 3 steps. The condensation of 2-imino-coumarine-3-carboxamides with cholic hydrazide in acetic acid with following recyclization in diphenyl ether formed the corresponding 1,3,4-oxadiazol-2-yl-coumarin derivatives in moderate to good yields. Structures of synthesized 7 examples fluorescent cholic-based derivatives were confirmed by NMR H¹ and MS. The UV-absorption and fluorescent spectrum of the newly synthesized compounds was measured in acetonitrile and ethanol solutions. It is shown that wave length of emitted irradiation is in the range from 420 to 510nm and quantum yield is in the range from 0,02 to 0,58. Either wave length or quantum yields depend on donation value and position of substitution group in coumarine fragment. Sensor-precursors that are developed in this way are very flexible to modifications. On the one hand, it\'s possible to modify easily the coumarine fragment in order to change the wavelength of fluorescence and color, respectively, on the other hand, by the introduction of various substituents on the hydroxyl groups in cholic fragment it\'s allowed to control the response level from attaching guest-substances.

Because of their ready availability, great structural and electronic diversity, easy handling and peculiar chemical behaviour organoselenium compounds are nowadays considered versatile reagents for many synthetic transformations. a,b-Unsaturated selenones represent an interesting example: the electron-withdrawing effect combined with the excellent nucleofugal ability of the phenylselenonyl group makes these compounds useful 1,2-bis(electrophilic) synthons. Recently we have conveniently employed readily available a,b-unsaturated selenones and 1,3-dicarbonyl compounds or cyanoacetates for the organocatalytic asymmetric assembly of structurally complex spirolactones or cyclopropanes. We now report some preliminary results concerning the use of phenyl vinyl selenone and cyclic b-ketoesters for the stereoselective formation of sterically constrained b-aminoesters containing two adjacent stereocenters. The sequential synthesis involves the following steps: a) a highly enantioselective Michael addition catalyzed by a cinchona alkaloid derived catalyst, b) the conversion of the resulting Michael adduct to the corresponding azide by nucleophilic substitution of the phenylselenonyl group, c) a cyclization reaction via a Staudinger/aza-Wittig sequence, d) a diastereoselective reduction of the resulting cyclic imine. b-Aminoesters are obtained with good yields and excellent stereocontrol.

In the past few decades, the synthesis of new heterocyclic compounds has been a subject of great interest due to their wide applicability. Among a large variety of heterocyclic compounds, heterocycles containing phthalazine moiety were reported to possess anticonvulsant, cardiotonic, and vasorelaxant activities. Therefore, a number of methods have been reported for the synthesis of phthalazine derivatives. Despite the available methods, the development of new synthetic methods for the efficient preparation of heterocycles containing phthalazine ring fragment is therefore an interesting challenge. With these precedents and with the aim of preparing new derivatives with potential pharmacological activity, we have synthesized new phthalazinedione derivatives by introducing halogenoalkyl substituents in one of the NH-nucleophilic groups. So, we started with 4-chloro-phthalic anhydride, which reacted with methyl- hydrazine, in MW mild conditions. After purification, we obtained two different isomers of phthalizediones, 8-chloro-2-methyl-2, 3-dihydro-phthalazine-1, 4-dione and 8-chloro-3-methyl-2, 3-dihydro-phthalazine-1,4-dione. Then halogenoalkyl substituents with different chain length were introduced in the nitrogen group in a very efficient way. Finally halogen atom of alkyl chains was replaced by an azide group. The described synthetic route will allow us to condense a nitrogen heterocyclic ring on the phatalazinone moiety and obtain a new tricyclic scaffold with promising pharmacological properties.

Selenium-based reagents bear a high potential for the improvement of known reactions not only from an environmental and pharmaceutical point of view, but also as interesting reagents for the development of, completely new synthetic transformations and as potential ligands in catalytic reactions. A variety of organoselenium compounds have been proven to be useful for organic synthesis over several decades. Organoselenium species can be introduced as either nucleophiles or electrophiles to other organic molecules, producing useful intermediates for organic synthesis. Optically active organoselenium derivatives and their application to highly selective asymmetric synthesis are also of current interest. Probably the most interesting aspect, which emerged in recent years, concerns the possibility of effecting some functional group conversions using catalytic amounts of the selenium reagent or using selenium containing compounds as chiral ligands in metal catalyzed reactions. The developments of all these catalytic processes represent the most important results which have been reported recently in this field and their conceptual and synthetic relevance considerably increases the use of some organoselenium derivatives as Green Catalysts. [1] In consideration that in Nature, the main biological function of selenium is associated with its incorporation in the form of selenocysteine (Sec) into certain proteins having redox motifs different selenium containing compounds can be investigated as bio-inspired catalysts in the carbon-carbon multiple bond oxidation mediated by H₂O₂ in water. These catalysts resulted to be also interesting good GPx-mimetics. Acknowledgement: Financial support from M.I.U.R.-PRIN2007, Consorzio CINMPIS, Bari, University of Perugia, the grant "British-Italian Partnership" from the British Council/CRUI. References [1] a) D. M. Freudendahl, S. Santoro, S. A. Shahzad, C. Santi, T. Wirth Angew. Chem. Int. Ed.2009, 8, 8409.b) C. Santi, M. Tiecco, L. Testaferri, C. Tomassini, S. Santoro, G. Bizzoca Phosphorus Sulfur Silicon Relat. Elem. 2008,183, 956. c) S. Santoro, C. Santi, M. Sabatini, L. Testaferri, M. Tiecco Adv.Synth. Catal. 2008, 350, 2881. d) S. Santoro, B. Battistelli, B. Gjoka, C-w.S.Si, L.Testaferri, M. Tiecco, C. Santi Synlett, 2010, 1402.

The nature of selenium-sulfur non-bonding interactions in a series of substituted benzeneselenenyl derivatives has been investigated by means of computational techniques. The results of these calculations, together with experimental measurements (X-rays crystallography and NMR), suggest that the strength of this interaction increases with the increase of electronegativity of the substituent on selenium. Natural bond orbital (NBO) analysis suggests that this interaction has a mainly covalent character, rather than electrostatic, and originates from an interaction between a lone pair of sulfur and an antibonding orbital on selenium. Atom in molecules (AIM) analysis further supports this finding.

The ring-opening of epoxides with different nucleophiles is an important strategy for the formation of 1,2-bifunctionalized building blocks. A wide variety of nucleophiles such as alcohols, phenols and carboxylic acids have been utilized in this reaction. Oxygen nucleophiles are among the most important ones as they lead to pharmaceutically important Þ-alkoxy and Þ-aryloxy alcohols.¹ Recently, we reported the first ring-opening of epichlorohydrin with salicylaldehyde derivatives in the presence of Jacobsen\' s Co(III)salen catalyst.² The final ring-opened product is a multifunctional aldehyde containing a stereocenter in addition to the alkyl halide and alcohol functional groups. In this study, we report the preparation of multifunctional chiral Schiff base ligands by the condesation of 4-(3-chloro-2-hydroxypropoxy)-2-hydroxybenzaldehyde with primary amines (2-aminophenol and 2-amino-2-methyl-1-propanol). The ligands have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopies. References 1. J. M. Ready, E. N. Jacobsen, J. Am. Chem. Soc., 1999, 121, 6086. 2. L. Karadeniz, G. Koz, K. Aydin, S. T. Astley, Turkish Journal of Chemistry, 2010, 34, 711.

An asymmetric aldol reaction is one of the most common methods for carbon-carbon bond formation in organic molecules. It is extensively applied in the synthesis of carbohydrates, amino sugares, steroids, and other valuable chiral organic compounds. It provides an atom-economic approach to β-hydroxyl carbonyls, which make up a large family of chiral intermediates for the synthesis of biologically active substances and natural products. In continuation of our research in environmentally benign and microwave assisted conditions, we now report an operationally simple and fast method for the preparation of aldol products by one-pot condition reaction. In this research, the direct aldol reaction of ketones with aromatic aldehydes using catalytic amount of RuCl₃.nH₂O and chiral ligand proceeded smoothly under extremely mild conditions to give the corresponding aldol adducts in good yields with moderate to good diastereoselectivity. The system can efficiently proceed at room temperature with a small excess of ketone. From a practical and economic point of view this reaction condition is convenient with respect to most of other protocols where a large excess of ketone is used. Also, microwave technique offers simple, clean, fast, efficient, and economic for the synthesis of a large number of aldol adducts. All the synthesized compounds are confirmed by spectroscopy methods such as ¹H-NMR, ¹³C-NMR and IR. Important advantages of this thechnology include highly accelerated rate of the reaction, reduction in reaction time with an improvement in the yield and quality of the products.

The development of new antimicrobial and anti cancer therapeutic agents is one of the fundamental goals in medicinal chemistry. Chiral thioureas and their derivatives display a wide range of biological activities such as antibacterial, antiviral and antifungal (1). In addition, some of these compounds could be used as catalysts in the asymmetric reactions such as the Michael addition to nitroalkenes and the Biginelli reaction. Therefore, recent efforts have been devoted to the synthesis of these compounds (2). In the light of this information, novel chiral thioureas bearing amino acids and 2-aminophenol moieties were synthesized in good yields and the structures of the compounds were characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR. References (1) Saeed, S., Rashid, N., Jones, P., Ali, M., Hussain, R., Eur. J. Med. Chem. 45, 2010, 1323-1331 (2) Sheng-Li, Z., Chang-Wu, Z., Gang, Z., Tetrahedron: Asymmetry, 20, 2009, 1046-1051

One of the most important transformations of glycidic esters is their decarboxylation to give rise to aldehydes and ketones. A proposed mechanism for the decomposition of the ethyl 3-phenyl glycidate indicates that the ethyl side of the ester is eliminated as ethylene through a concerted six-membered cyclic transition state, and the unstable intermediate glycidic acid rapidly decarboxylates to give the corresponding aldehyde. Two possible pathways for the glycidic acid decarboxylation were proposed, one of them via a five-membered cyclic transition state and the other one via a four-membered cyclic transition state(Chuchani, G.; Tosta, M.; Rotinov, A.; Herize, A. J. Phys. Org. Chem. 2004, 17, 694). An accurate experimental description of the glycidic acid decarboxylation is a challenging task, since the glycidic acids decompose even at room temperature. Therefore, the goal of this work is investigated the path more favored by decarboxylation. Theoretical calculations were carried out in order to probe this proposed mechanism. Geometries of the different reactants, products and intermediates were optimized at different levels of calculation. The vibrational frequencies were calculated at the same level. The results were compared with those from experiments. Theoretical calculations indicate that the glycidic acid decarboxylation occurs via a five-membered cyclic transition state.