Antonio Rescifina

Recent advances in small organic molecules as DNA intercalating agents: Synthesis, activity, and modeling

The interaction of small molecules with DNA plays an essential role in many biological processes. As DNA is often the target for majority of anticancer and antibiotic drugs, study about the interaction of drug and DNA has a key role in pharmacology. Moreover, understanding the interactions of small molecules with DNA is of prime significance in the rational design of more powerful and selective anticancer agents. Two of the most important and promising targets in cancer chemotherapy include DNA alkylating agents and DNA intercalators. For these last the DNA recognition is a critical step in their anti-tumor action and the intercalation is not only one kind of the interactions in DNA recognition but also a pivotal step of several clinically used anti-tumor drugs such as anthracyclines, acridines and anthraquinones. To push clinical cancer therapy, the discovery of new DNA intercalators has been considered a practical approach and a number of intercalators have been recently reported. The intercalative binding properties of such molecules can also be harnessed as diagnostic probes for DNA structure in addition to DNA-directed therapeutics. Moreover, the problem of intercalation site formation in the undistorted B-DNA of different length and sequence is matter of tremendous importance in molecular modeling studies and, nowadays, three models of DNA intercalation targets have been proposed that account for the binding features of intercalators. Finally, despite DNA being an important target for several drugs, most of the docking programs are validated only for proteins and their ligands. Therefore, a default protocol to identify DNA binding modes which uses a modified canonical DNA as receptor is needed.

A DFT study on the 1,3-dipolar cycloaddition reactions of C-(methoxycarbonyl)-N-methyl nitrone with methyl acrylate and vinyl acetate

In the 1,3-dipolar cycloaddition of glyoxylic nitrones with electron-poor and electron-rich alkenes, the configurational instability of the nitrone leads to parallel models when regio- and stereoselectivities are rationalized. The energetics of the cycloaddition reactions have been investigated through molecular orbital calculations at the B3LYP/6-31-G(d) theory level. By studying different reaction channels and reagent conformations, leading to a total of sixteen transition structures for each dipolarophile, the regio- and stereochemical preferences of the reaction are discussed.

One-flask transformation of secondary amines to nitrones by oxidation with hydrogen peroxide mediated by triscetylpyridinium tetrakis oxodiperoxotungsto-phosphate (PCWP). Some mechanistic considerations

Abstract Acyclic and cyclic secondary amines are oxidized to nitrones by H 2 O 2 /PCWP system in water/chloroform under phase transfer catalysis conditions. The different acidities of the protons of the carbon atoms α to the nitrogen might be responsible for the identity and ot the stereochemistry of the formed nitrone. The presence of an aromatic ring such as benzene directly linked to the nitrogen represents a limitation, since in this case many oxidation products are observed. As far as the mechanistic aspects are concerned, it is suggested that the oxidation process might be started by a nucleophilic attack of the amine to the peroxidic oxygens of the peroxometal complex or by a single electron transfer from the amine to the oxidant.

Histone methyltransferase inhibitors: novel epigenetic agents for cancer treatment.

Epigenetics is defined as heritable changes in gene activity and expression that occur without alteration in DNA sequence. The gene transcription is strictly correlated to chromatin structure, which could undergo covalent modifications of histones involving acetylation, methylation, phosphorylation and ubiquitination. Alterations in histones are implicated in many diseases, including cancer, by leading to tumor suppressor silencing or pro-apoptotic proteins downregulation. Although post-translational addition of methyl groups to the histone lysine has been discovered three decades ago, the importance of this epigenetic modification has emerged only in the last few years. Thenceforward histone methyltransferase inhibitors have been developed as potential therapeutic cancer agents. It should not be long before some selective inhibitors make their way into clinical trials. This review is mainly focused on the evolution in the development of new epigenetic modifier molecules modulating histone marks.

Isoxazolidine analogues of pseudouridine: a new class of modified nucleosides

Abstract A new class of modified C-nucleosides has been synthesized according to the 1,3-dipolar cycloaddition methodology. The obtained compounds are structurally related to natural pseudouridine, where the sugar moiety is replaced by an isoxazolidine ring. Different experimental conditions, and the effect of additives on the cycloaddition process, have been examined; the best results were obtained when the cycloaddition reaction was performed under microwave irradiation

MODIFIED DIDEOXYNUCLEOSIDES : SYNTHESIS OF 2'-N-ALKYL-3'-HYDROXYALKYL-1',2'-ISOXAZOLIDINYL THYMIDINE AND 5-FLUOROURIDINE DERIVATIVES

Abstract Isoxazolidine nucleosides bearing an hydroxyl group at C3, have been prepared in only three steps, with overall high yields. The synthetic approach is based on the 1,3-dipolar cycloaddition of 3-carboxyalkyl- or acylnitrones to vinyl acetate, followed by condensation with silylated thymine or 5-fluorouracil and NaBH4 reduction.

C-Alkoxycarbonyl Nitrones: Building Blocks for the Synthesis of Butenolides, Lactams and Modified Nucleosides

Abstract: Elaboration of isoxazolidines derived from the 1,3-dipolar cycloaddition of C-alkoxycarbonyl nitrones to suitably substituted alkenes leads to the development of new synthetic methodologies for the preparation of a wide range of natural products and derivatives including lactones, lactams and complex nucleosides. The insertion of a chiral centre in position α, with respect to nitrone functionality, or the presence of a chiral auxiliary at the nitrogen atom have allowed the enantioselective synthesis of the same compounds.

Diastereo- and enantioselective synthesis of N,O-nucleosides

Abstract The diastereo- and enantioselective synthesis of α- and β-3′-hydroxymethyl-N,O-nucleosides is described, based on the 1,3-dipolar cycloaddition of a N-glycosyl nitrone. Two approaches have been evaluated: the one-step procedure, which uses vinyl nucleobases, showed a better stereoselectivity towards β-nucleosides.

Stereoselective synthesis of homochiral annulated sultams via intramolecular cycloaddition reactions

Abstract Different homochiral dipoles containing a sulfonamido group have been synthesized, starting from l -amino acids, and used for the construction of functionalized and enantiomerically pure annulated sultams.

Enantioselective synthesis of 4-hydroxy-d-pyroglutamic acid derivatives by an asymmetric 1,3-dipolar cycloaddition

Abstract The 1,3-dipolar cycloaddition of a chiral nitrone derived from glyoxylic acid and protected d -ribosyl hydroxylamine with the acrylamide of Oppolzers sultam provides a perfectly stereoselective approach to protected (2 R ,4 R )-4-hydroxy- d -pyroglutamic acid.