SYNTHESIS OF RACEMIC AND ENANTIOMERIC 3-PYRROLIDINYL DERIVATIVES OF PURINE AND PYRIMIDINE NUCLEOBASES

The present work relates to the synthesis of pyrrolidine nucleoside analogs. Starting from malic acid, we have elaborated a high-yield synthesis of racemic and enantiomeric N-protected 3-pyrrolidinols and their O-mesyl derivatives as key compounds for alkylations of purine and pyrimidine nucleobases. On varying base and solvent, we have found conditions providing both satisfactory N-/O-regioisomeric ratio and acceptable yield for pyrimidine compounds.     

The metabolism of pyrimidine compounds by Tetrahymena pyriformis

The pyrimidine requirements for growth of T. pyriformis and for reversal of the growth inhibition caused by folate deprivation have been studied. The effects of thymidine and 5-fluorodeoxyuridine have been shown to be quantitatively different from the effects of these compounds on growth and the rate of DNA synthesis in mammalian cells. Labelled nucleosides added to the medium have been found to be converted to the corresponding bases with the exception of deoxycytidine, which is first deaminated to deoxyuridine. As a result no deoxynucleosides other than thymidine specifically label DNA. The results allow deductions to be made concerning the enzymes involved in pyrimidine utilization by this organism. It is suggested that pyrimidine utilization is always channeled through uracil in the case of those compounds that can supply the pyrimidine requirement for growth.     

Serendipitous discovery of 2-((phenylsulfonyl)methyl)-thieno[3,2-d]pyrimidine derivatives as novel HIV-1 replication inhibitors

We identified a novel class of 2-((phenylsulfonyl)methyl)-thieno[3,2-d]pyrimidine compounds as potent HIV-1 replication inhibitors serendipitously during the process of evaluation of triazolothienopyrimidine (TTPM) compounds. Herein, we report synthesis and biological evaluation of 2-((phenylsulfonyl)methyl)-thieno[3,2-d]pyrimidine compounds using a cell-based full replication assay to identify thienopyrimidines 6 and 30, which could be further utilized as viable lead compounds.     

2-Alkyl-4-aryl-pyrimidine fused heterocycles as selective 5-HT2A antagonists

The synthesis and SAR for a novel series of 2-alkyl-4-aryl-tetrahydro-pyrido-pyrimidines and 2-alkyl-4-aryl-tetrahydro-pyrimido-azepines is described. Representative compounds were shown to be subtype selective 5-HT(2A) antagonists. Optimal placement of a basic nitrogen relative to the pyrimidine and the presence of a 4-fluorophenyl group in the pyrimidine 4-position was found to have a profound effect on affinity and selectivity.     

The synthesis and SAR of 2-amino-pyrrolo[2,3-d]pyrimidines: a new class of Aurora-A kinase inhibitors

A new class of Aurora-A inhibitors have been identified based on the 2-amino-pyrrolo[2,3-d]pyrimidine scaffold. Here, we describe the synthesis and SAR of this novel series. We report compounds which exhibit nanomolar activity in the Aurora-A biochemical assay and are able to inhibit tumor cell proliferation. This study culminates in compound 30, an inhibitor with potent activity against Aurora A (IC50=0.008 microM), anti-proliferative activity against several tumor cell lines and induces polyploidy in H460 cells.     

Biosynthesis of the Pyrimidine Moiety of Thiamine Independent of the PurF Enzyme (Phosphoribosylpyrophosphate Amidotransferase) in Salmonella typhimurium: Incorporation of Stable Isotope-Labeled Glycine and Formate

Genetic analyses have suggested that the pyrimidine moiety of thiamine can be synthesized independently of the first enzyme of de novo purine synthesis, phosphoribosylpyrophosphate amidotransferase (PurF), in Salmonella typhimurium. To obtain biochemical evidence for and to further define this proposed synthesis, stable isotope labeling experiments were performed with two compounds, [2-¹³C]glycine and [¹³C]formate. These compounds are normally incorporated into thiamine pyrophosphate (TPP) via steps in the purine pathway subsequent to PurF. Gas chromatography-mass spectrometry analyses indicated that both of these compounds were incorporated into the pyrimidine moiety of TPP in a purF mutant. This result clearly demonstrated that the pyrimidine moiety of thiamine was being synthesized in the absence of the PurF enzyme and strongly suggested that this synthesis utilized subsequent enzymes of the purine pathway. These results were consistent with an alternative route to TPP that bypassed only the first enzyme in the purine pathway. Experiments quantitating cellular thiamine monophosphate (TMP) and TPP levels suggested that the alternative route to TPP did not function at the same capacity as the characterized pathway and determined that levels of TMP and TPP in the wild-type strain were significantly altered by the presence of purines in the medium.     

Synthesis and anti-HIV-1 activity of a novel series of 1,4,2-benzodithiazine-dioxides

Previously, we discovered a series of novel benzodithiazines-dioxides with both antiviral and anticancer activities. In order to design compounds with distinct antiviral properties, we prepared new compounds with modifications on the imidazole and pyrimidine rings. Herein, we present the synthesis and antiviral activity of 8-chloro-2,3-dihydroimidazo[1,2-b][1,4,2]benzodithiazine 5,5-dioxides (22, 23, 30, and 31) and 9-chloro-2,3,4-trihydropyrimido[1,2-b][1,4,2]benzodithiazine 6,6-dioxides (14, 24, 25, and 27). We successfully identified a lead compound with remarkable anti-HIV-1 activity (EC(50)=0.09microM). These compounds showed minimal cytotoxicity and are therefore suitable for antiviral development.     

Bicyclic furano-, pyrrolo-, and thiopheno[2,3-d] derivatives of pyrimidine nucleosides: Synthesis and antiviral properties

The methods of synthesis of furano-, thiopheno-, and pyrrolo[2,3-d]pyrimidine deoxyribonucleosides and their derivatives and studies of the relationship between the structure and the antiviral activity of these compounds towards the viruses of varicella zoster, hepatitis C, and others have been reviewed.     

Studies on the Accumulation of Orotic Acid by Escherichia coli K12

The mechanism whereby Escherichia coli K12 accumulates orotic acid in culture fluid was studied. Pyrimidine compounds were incorporated effectively into cells of E. coli K12, stimulated the growth, and depressed the accumulation; while purine compounds were not so much consumed by the microorganism for its growth, and affected the accumulation to a lesser extent. On the other hand, E. coli B unable to accumulate orotic acid utilized less effectively pyrimidine compounds for its growth than strain K12.

It is supposed, therefore, that in the de novo pathway for pyrimidine synthesis in E. coli K12 the step from orotic acid to 5′-UMP is genetically depressed so that orotic acid is accumulated when pyrimidine compounds, that would cause a feedback inhibition of orotic acid synthesis upon incorporation, are not supplemented.     

Exploratory studies to investigate a linked prebiotic origin of RNA and coded peptides. 3rd communication. Behaviour of 5-amino-1H-imidazole-4-carbonitrile derivatives

The potentially prebiotic synthesis of pyrimidine ribonucleotides by stepwise nucleobase assembly on arabinose-3-phosphate derivatives has been demonstrated in previous work. The generation of xylose-2-phosphate derivatives by aldolisation, and the behaviour of these compounds under the conditions of pyrimidine nucleobase assembly have also been described. In this paper, the scope for generation of purine nucleotides via 3,3'-anhydro-xylo-nucleotides is investigated. In neutral D2O solution, the potential intermediate 47 (Schemes 6 and 8) undergoes H-C2 --> D-C2 exchange, but no appreciable reaction with cyanide or cyanamide occurs. The exchange chemistry expands options for purine nucleobase assembly on sugar phosphate scaffolds.     

New potential calcium channel modulators: design and synthesis of compounds containing two pyridine, pyrimidine, pyridone, quinoline and acridine units under microwave irradiation

The synthesis of bifunctional pyridine, pyrimidine, pyridone, quinoline and acridine derivatives was investigated using dialdehyde as a precursor. A rapid and efficient method was developed for the synthesis of a range of bifunctional monocyclic, bicyclic and tricyclic products related to 1,4-DHPs with the aim of finding new classes of biologically active compounds.     

The Role of the Formamide/Zirconia System in the Synthesis of Nucleobases and Biogenic Carboxylic Acid Derivatives

We describe the one-pot synthesis of a large variety of nucleic acid bases and related compounds from formamide in the presence of zirconium minerals as catalysts. The major products observed are: purine, 2-hydroxy pyrimidine, 5-hydroxy pyrimidine, isocytosine, adenine, urea, and carbodiimide. The synthesis of low molecular weight amides and carboxylic acid derivatives (intermediates of extant metabolism) was also observed: glyoxylamide, glycolic-, lactic-, succinic-, oxalic-, fumaric-, and maleic acids. As the major problem in the origin of informational polymers is the instability of their precursors, we also investigated the effects of zirconia minerals on the stability of ribooligonucleotides in formamide and in water. The relevance of these findings with respect to the origin of informational polymers and primordial metabolism is discussed.     

Design, synthesis and antibacterial activity of novel 1,3-thiazolidine pyrimidine nucleoside analogues

The synthesis of a new class of 1,3-thiazolidine nucleoside analogues in which furanose oxygen atom was replaced with nitrogen atom and 2'-carbon atom with sulfur atom is described. N-tert-butoxycarbonyl-2-acyloxy-4-trityloxymethyl-1,3-thiazolidine was coupled with the pyrimidine bases like uracil, thymine, etc. in the presence of lewis acids stannic chloride or trimethyl silyl triflate following Vorbruggen procedure. The antibacterial activity of the novel 1,3-thiazolidine pyrimidine nucleoside analogues is highlighted. All compounds (7a-e) with free NH group in the pyrimidine moiety showed significant biological activity against all the standard strains used and in that compounds 7d and 7e showed significant activity against 14 human pathogens tested.     

Repression of Escherichia coli carbamoylphosphate synthase: relationships with enzyme synthesis in the arginine and pyrimidine pathways.

Cumulative repression of Escherichia coli carbamoylphosphate synthase (CPSase; EC 2.7.2.9) by arginine and pyrimidine was analyzed in relation to control enzyme synthesis in the arginine and pyrimidine pathways. The expression of carA and carB, the adjacent genes that specify the two subunits of the enzyme, was estimated by means of an in vitro complementation assay. The synthesis of each gene product was found to be under repression control. Coordinate expression of the two genes was observed under most conditions investigated. They might thus form an operon. The preparation of strains blocked in the degradation of cytidine and harboring leaky mutations affecting several steps of pyrimidine nucleotide synthesis made it possible to distinguish between the effects of cytidine and uridine compounds in the repression of the pyrimidine pathway enzymes. The data obtained suggest that derivatives of both cytidine and uridine participate in the repression of CPSase. In addition, repression of CPSase by arginine did not appear to occur unless pyrimidines were present at a significant intracellular concentration. This observation, together with our previous report that argR mutations impair the cumulative repression of CPSase, suggests that this control is mediated through the concerted effects of regulatory elements specific for the arginine and pyrimidine pathways.     

Identification of potent pyrimidine inhibitors of phosphodiesterase 7 (PDE7) and their ability to inhibit T cell proliferation

A series of pyrimidine based inhibitors of PDE7 are discussed. The synthesis, structure–activity relationships (SAR) and selectivity against several other PDE family members as well as activity in T cells are presented. These compounds were found to have effects on T cell proliferation, however it is not clear whether the mechanism is related to PDE7 inhibition.     

Key role of uridine kinase and uridine phosphorylase in the homeostatic regulation of purine and pyrimidine salvage in brain

Uridine, the major circulating pyrimidine nucleoside, participating in the regulation of a number of physiological processes, is readily uptaken into mammalian cells. The balance between anabolism and catabolism of intracellular uridine is maintained by uridine kinase, catalyzing the first step of UTP and CTP salvage synthesis, and uridine phosphorylase, catalyzing the first step of uridine degradation to β-alanine in liver. In the present study we report that the two enzymes have an additional role in the homeostatic regulation of purine and pyrimidine metabolism in brain, which relies on the salvage synthesis of nucleotides from preformed nucleosides and nucleobases, rather than on the de novo synthesis from simple precursors. The experiments were performed in rat brain extracts and cultured human astrocytoma cells. The rationale of the reciprocal regulation of purine and pyrimidine salvage synthesis in brain stands (i) on the inhibition exerted by UTP and CTP, the final products of the pyrimidine salvage pathway, on uridine kinase and (ii) on the widely accepted idea that pyrimidine salvage occurs at the nucleoside level (mostly uridine), while purine salvage is a 5-phosphoribosyl-1-pyrophosphate (PRPP)-mediated process, occurring at the nucleobase level. Thus, at relatively low UTP and CTP level, uptaken uridine is mainly anabolized to uridine nucleotides. On the contrary, at relatively high UTP and CTP levels the inhibition of uridine kinase channels uridine towards phosphorolysis. The ribose-1-phosphate is then transformed into PRPP, which is used for purine salvage synthesis.     

Pyrimidine containing RSV fusion inhibitors

The knowledge of SAR in a series of biphenyl anionic RSV inhibitors has been broadened by synthesis and testing of analogs with pyrimidine linkers. Generally, pyrimidine compounds were much harder to synthesize, and their anti-RSV activity was lower in comparison with triazine analogs.     

Key role of uridine kinase and uridine phosphorylase in the homeostatic regulation of purine and pyrimidine salvage in brain

Uridine, the major circulating pyrimidine nucleoside, participating in the regulation of a number of physiological processes, is readily uptaken into mammalian cells. The balance between anabolism and catabolism of intracellular uridine is maintained by uridine kinase, catalyzing the first step of UTP and CTP salvage synthesis, and uridine phosphorylase, catalyzing the first step of uridine degradation to β-alanine in liver. In the present study we report that the two enzymes have an additional role in the homeostatic regulation of purine and pyrimidine metabolism in brain, which relies on the salvage synthesis of nucleotides from preformed nucleosides and nucleobases, rather than on the de novo synthesis from simple precursors. The experiments were performed in rat brain extracts and cultured human astrocytoma cells. The rationale of the reciprocal regulation of purine and pyrimidine salvage synthesis in brain stands (i) on the inhibition exerted by UTP and CTP, the final products of the pyrimidine salvage pathway, on uridine kinase and (ii) on the widely accepted idea that pyrimidine salvage occurs at the nucleoside level (mostly uridine), while purine salvage is a 5-phosphoribosyl-1-pyrophosphate (PRPP)-mediated process, occurring at the nucleobase level. Thus, at relatively low UTP and CTP level, uptaken uridine is mainly anabolized to uridine nucleotides. On the contrary, at relatively high UTP and CTP levels the inhibition of uridine kinase channels uridine towards phosphorolysis. The ribose-1-phosphate is then transformed into PRPP, which is used for purine salvage synthesis.     

The isolation and genetic characterization of X-linked mutations that affect pyrimidine metabolism in Drosophila melanogaster

Summary This paper focuses on the number of X-linked genes which play a role in pyrimidine metabolism. A series of mutation screens have been carried out for the following types of mutants: (a) mutants which reduce pyrimidine synthesis, (b) mutants which reduce pyrimidine catabolism, and (c) mutants which are unable to utilize dietary pyrimidines and depend upon de novo synthesis for survival. The genetic characterization of the 95 X-linked mutants obtained indicates that there are very few X-linked genes which play a direct role in pyrimidine metabolism.