New trends in synthesis of pyrazole nucleosides as new antimetabolites

Pyrazole nucleosides and condensed pyrazole nucleosides exhibit various biological activities. This article describes recent synthetic approaches to their preparation, chemical properties, biological activities, and structure-activity relationships, with emphasis to selected drugs or drug candidates. Two pyrazole C-nucleoside compounds pyrazofurin (pyrazomycin) and its alpha-epimer pyrazofurin B are active components of potent antivirals approved for therapeutic use in human medicine aimed against various diseases caused by DNA viruses.

Thioguanine, Mercaptopurine: Their Analogs and Nucleosides as Antimetabolites

6-Mercaptopurine (6MP) and 6-thioguanine (6TG) are analogs of the natural purines: hypoxanthine and guanine. Both mercaptopurine and thioguanine are substrates for hypoxanthine-guanine phosphoribosyltransferase and are converted into the ribonucleotides 6-thioguanosine monophosphate (6-thioGMP) and 6-thioinosine monophosphate (T-IMP) respectively. The accumulation of these monophosphates inhibits several vital metabolic reactions. Today, these thiopurine bases remain valuable agents for the induction and maintenance of remissions in patients with myelocytic and acute lymphocytic leukemia. Despite their proved clinical importance, 6MP and 6TG have certain therapeutic disadvantages, which have continued to stimulate the search for purine derivatives enhancing therapeutic efficacy. Considerable efforts have been made to prepare other novel mercaptopurine and thioguanine analogs and their nucleosides to improve the antitumor efficacy. The effectiveness of these thiopurines against certain tumor cell lines suggested that some of these mercaptopurine analogs and their nucleosides would be worthy of consideration in order to determine whether they exert a more selective effect against neoplastic cells than against normal cells or they might be useful in patients whose disease has become resistant to 6MP or 6TG. This review will focus on mercaptopurine analogs and their nucleosides as antimetabolite agents.

A new class of biheterocyclic thioglycosides from pyridine-2-(1H)-thiones

A reported method for preparation of a new class of biheterocyclic thioglycosides via reaction of pyridinethiones with 2,3,4,6-tetra-O-acetyl-alpha-D-gluco- and galactopyranosyl bromides has been studied.

Nucleic acid components and their analogues: a novel and efficient method for the synthesis of a new class of bipyridyl and biheterocyclic-nitrogen thioglycosides from pyridine-2(1H)-thiones

A novel synthesis of a new class of bipyridyl and biheterocyclic-nitrogen thioglycosides utilizing the reactions of heterocyclic substituted pyridine-2(1H)-thiones and alpha-bromoglucose or alpha-bromogalactose tetraacetate as starting components is described.

A direct route to 2-(beta-D-ribofuranosylthio)pyridine glycosides

A novel synthesis of a new class of 2-(beta-D-ribofuranosylthio)pyridine glycosides utilizing the reactions of substituted pyridine-2(1H)-thiones and 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose as starting components is described.

Pyrimidinethione nucleosides and their deaza analogues

The methods of preparation, structure, chemical properties and synthetic potentiality of pyrimidinethione nucleosides and their deaza analogues are reported.