Roberto Romeo

Highly efficient and versatile acetylation of alcohols catalyzed by cerium(III) triflate

Cerium(III) triflate is a powerful catalyst for the acetylation of alcohols. The reaction works well for a large variety of simple and functionalized alcohols, without isomerisation of chiral centres. Changes of hydroxyl protective groups are possible in a one-pot procedure. The catalyst can be easily recycled.

Synthesis and Biological Activity of Phosphonated Nucleosides: Part 1Furanose, Carbocyclic and Heterocyclic Analogues

Phosphonated nucleosides represent a promising alternative in the improvement of the biological activity of nucleoside analogues in antiviral and anticancer chemotherapy. The basic concept, the chemistry, the different structural modifications and their effects on the antiviral potency will be discussed in this review.

Determination of oxygen heterocyclic components in citrus products by HPLC with UV detection.

The study of oxygen heterocyclic compounds (coumarins, psoralens, polymethoxylated flavones) in natural matrices such as citrus oils is not easy due to the difficulty of obtaining standards at the required level of purity and the diversity of structures present in each kind of sample. In this work, standards were either isolated by preparative LC methods from citrus oils or synthesized, then characterized by their physicochemical parameters and spectroscopic techniques, and further used for qualitative and quantitative calculations in citrus essential oils and products made with them (Earl Grey tea, liquors, juices). An HPLC method using an innovative partially porous particle HPLC column enabled baseline separation of all analytes. The method developed was validated in terms of detection limit, quantitation limit, linearity, and precision as repeatability and intralaboratory reproducibility.

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

Experimental and theoretical study of the 1,3-dipolar cycloaddition between d-glyceraldehyde nitrones and acrylates. Diastereoselective approach to 4-hydroxy pyroglutamic acid derivatives

Abstract The 1,3-dipolar cycloaddition reactions of five d -glyceraldehyde nitrones with alkyl acrylates and Oppolzers sultam acrylamide have been studied in detail, the study including double chiral induction experiments. A complete theoretical study of the reaction has also been carried out using density functional methods (B3LYP/6-31G*) in which both ortho and meta channels leading to 3,5- and 3,4-disubstituted isoxazolidines, respectively, were considered. The adducts obtained from the cycloaddition reactions have been further used for the stereoselective synthesis of protected 4-hydroxy pyroglutamic acids, particularly the (2S,4S)-isomer, which is prepared from the major adducts of the cycloaddition reactions.

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.

Antiviral activity of seed extract from Citrus bergamia towards human retroviruses

The effects of an extract from Citrus bergamia (BSext) and those of two products purified from the same extract, that is, nomilin and limonin, and reference compounds, towards HTLV-1 have been reported. Moreover, they were also compared with those obtained towards HIV-1. Results showed that the efficacy of both BSext and limonin in inhibiting HTLV-1 as well as HIV-1 expression in infected cells, as evaluated by comparable quantitative assays, was close to that of the effective, reference compounds, respectively. The protective effect of BSext and of the purified products was associated with the inhibition of both HTLV-1 and HIV-1 RT activities in conceptually similar, cell-free assays. The cytotoxicity of the assayed compounds of natural origin was substantially less pronounced than that of the reference compounds, thus showing a favourable selectivity index for the novel BSext product.

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.

α-Amino acids as chiral educts for stereoselective syntheses of pyrrolidine and pyrrolizidine systems☆

Abstract Homochiral functionalized pyrrolidine and pyrrolizidine systems have been achieved by stereoselective intramolecular 1,3-dipolar cycloaddition of homochiral nitrones, starting from homochiral amino acids, and by subsequent reduction of the obtained cycloadducts.