Zinc(II) Triflate-Controlled 1,3-Dipolar Cycloadditions of C-(2-Thiazolyl)nitrones: Application to the Synthesis of a Novel Isoxazolidinyl Analogue of Tiazofurin

Mechanochemical Synthesis of Primary Amides

Ball milling of aromatic, heteroaromatic, vinylic, and aliphatic esters with ethanol and calcium nitride afforded the corresponding primary amides in a transformation that was compatible with a variety of functional groups and maintained the integrity of a stereocenter α to carbonyl. This methodology was applied to α-amino esters and N-BOC dipeptide esters and also to the synthesis of rufinamide, an antiepileptic drug.

C-Nucleosides To Be Revisited

Two new C-nucleoside analogues, BCX4430, an imino-C-nucleoside, and GS-6620, a phosphoramidate derivative of 1'-cyano-2'-C-methyl-4-aza-7,9-dideazaadenosine C-nucleoside, have been recently described as effective against filovirus infections (Marburg) and hepatitis C virus (HCV), respectively. The first C-nucleoside analogues were described about half a century ago. The C-nucleoside pseudouridine is a natural component of RNA, and various other C-nucleoside analogues have been reported previously for their antiviral and/or anticancer potential, the most prominent being pyrazofurin, tiazofurin, and selenazofurin. In the meantime, showdomycin, formycin, and various triazole, pyrazine, pyridine, dihydroxyphenyl, thienopyrimidine, pyrazolotriazine, and porphyrin C-nucleoside analogues have been described. It would be worth revisiting these C-nucleosides and derivatives thereof, including their phosphoramidates, for their therapeutic potential in the treatment of virus infections and, where appropriate, cancer as well.

Synthesis and biological properties of 5-(1H-1,2,3-triazol-4-yl)isoxazolidines: a new class of C-nucleosides

A novel series of C-nucleosides, featuring the presence of a 1,2,3-triazole ring linked to an isoxazolidine system, has been designed as mimetics of the pyrimidine nucleobases. An antiproliferative effect was observed for compounds 17a and 17b: the growth inhibitory effect reaches the 50% in HepG2 and HT-29 cells and increases up to 56% in the SH-SY5Y cell line after 72 h of incubation at a 100 µM concentration.

Synthesis of novel aza-analogues of tiazofurin with 2-[5,5-bis(hydroxymethyl)pyrrolidin-2-yl] framework as sugar mimic

The novel aza-analogues of tiazofurin (TZF) with 2-[5,5-bis(hydroxymethyl)pyrrolidin-2-yl] moiety, as sugar mimic, were synthesized from O,O-cyclohexylidene derivative of 4,4-bis(hydroxymethyl)-4-nitrobutanal in multi-gram scale. The synthetic route consisted of three stages: (i) the synthesis of corresponding derivative of 5,5-bis(hydroxymethyl)pyrrolidine-2-carbonitrile, (ii) the construction of ethyl thiazole-2-carboxylate part by the conversion of the pyrrolidine-2-carbonitrile into the N-trifluoroacetyl derivative followed by cyclocondensation with L-cysteine ethyl ester and then by dehydrogenation, and (iii) the final transformation of the ethyl thiazole-4-carboxylate into the aza-analogues of TZF. The TZF aza-analogues were evaluated for their antiviral activities in cell-culture-based assays.

Microwave-assisted syntheses of nucleosides and their precursors

In recent decades, nucleosides analogs have been the cornerstone in the treatment of various diseases, such as AIDS, herpes and hepatitis. More than 40 modified nucleosides are officially approved by the US FDA and represent the major compound class for inhibition of viral replication. By comparison with traditional conditions, microwave irradiation offers a powerful tool that can increase yields and decrease reaction time, with simple manipulation and an environmentally friendly way. Here, we report the latest progress in nucleoside synthesis using microwave irradiation.

Synthesis and antitumour activity of new tiazofurin analogues bearing a 2,3-anhydro functionality in the furanose ring

This paper describes a divergent de novo synthesis of 2-(2,3-anhydro-beta-dribofuranosyl)thiazole-4-carboxamide (2',3'-anhydro-tiazofurin) and the corresponding alpha- and beta-homo-C-nucleosides, as well as evaluation of their antitumour activities in vitro.

Transition structures of diastereoselective 1,3-dipolar cycloadditions of nitrile oxides to chiral homoallylic alcohols

Transition structures of the 1,3-dipolar cycloaddition of substituted nitrile oxides with chiral homoallylic alcohols were explored with density functional theory (B3LYP/6-311+G(d,p)+CPCM(dichloromethane)//B3LYP/6-31+G(d)). The diastereoselectivity observed in these reactions was explained. The anti product is favored in both the thermal and magnesium-mediated reactions. Selectivity is predicted to increase in the presence of magnesium, in agreement with experimental results. The energetics of the magnesium-mediated reaction are similar to those previously found for allylic alcohols. [structure: see text].

2-(3-Amino-3-deoxy-β-d-xylofuranosyl)thiazole-4-carboxamide: A new tiazofurin analogue with potent antitumour activity

A new tiazofurin analogue, 2-(3-amino-3-deoxy-beta-d-xylofuranosyl)thiazole-4-carboxamide (3), was synthesized starting from d-glucose and evaluated for its in vitro antiproliferative activity against a panel of human tumour cell lines. Compound 3 exhibited the most powerful cytotoxicity against K562 cells, being approximately 100-fold more potent than tiazofurin. This analogue was also active against Jurkat, HT-29 and HeLa malignant cells, with respective IC(50) values being ca. 2-, 27- and 17-fold lower than those observed for tiazofurin. Remarkably, compound 3 did not exhibit any significant cytotoxicity towards normal foetal lung MRC-5 cell line.

Enantiodivergent Synthesis of d- and l-erythro-Sphingosines through Mannich-Type Reactions of N-Benzyl-2,3-O-isopropylidene-d-glyceraldehyde Nitrone

The addition of a 2-silyloxy silylketene acetal to N-benzyl-2,3-O-isopropylidene-D-glyceraldehyde nitrone (Mannich-type reaction) can be stereocontrolled to give 2S,3S,4S and 2R,3R,4S adducts as major compounds, depending on whether the reaction is activated with zinc(II) triflate or tin(IV) chloride, respectively. The corresponding major adducts were used for preparing diastereomeric polyhydroxy-beta-aminoesters that were further converted into suitable orthogonally protected enantiomeric D- and L-erythro-sphingosines.