Pyrimidine Ribonucleosides Research Articles

ChemInform Abstract: Partial Protection of Carbohydrate Derivatives. Part 14. Regioselective Phenylcarbamoylation of Purine and Pyrimidine Ribonucleosides Through Dibutyltin Oxide‐ and Tertiary Amine‐Phenyl Isocyanate Systems.

ChemInformVolume 18, Issue 19 Natural Products ChemInform Abstract: Partial Protection of Carbohydrate Derivatives. Part 14. Regioselective Phenylcarbamoylation of Purine and Pyrimidine Ribonucleosides Through Dibutyltin Oxide- and Tertiary Amine-Phenyl Isocyanate Systems. I. HIRAO, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorK. ITOH, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorS. NISHINO, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorY. ARAKI, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorY. ISHIDO, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this author I. HIRAO, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorK. ITOH, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorS. NISHINO, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorY. ARAKI, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this authorY. ISHIDO, Dep. Chem., Fac. Sci., Tokyo Inst. Technol., Ookayama, Meguro-ku, Tokyo 152, JapanSearch for more papers by this author First published: May 12, 1987 https://doi.org/10.1002/chin.198719335AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue19May 12, 1987 RelatedInformation

Precursors of ribose 5-phosphate suppress expression of glucose-regulated proteins in LLC-PK1 cells.

Withdrawal of glucose from the medium bathing mammalian cells in culture results in cessation of growth and induces the synthesis of two stress proteins (Mr approximately 94-100 kDa and 78-80 kDa) that have been termed glucose-regulated proteins (GRPs). In LLC-PK1 cells, proteins of the same molecular weights, assayed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography, are fully induced by 24 h in glucose-free medium. The GRPs from LLC-PK1 cells cross-react with antibodies to GRPs of nonpolar cells, confirming their identification. Since glucose is not essential for energy production in cultured cells, but is essential for ribose 5-phosphate and nucleotide biosynthesis (Wice et al. J. Biol. Chem. 256: 7812-7819, 1981), we tested the effect of several precursors of ribose 5-phosphate on the induction of GRPs. The addition of 25 mM fructose or galactose to glucose-free medium suppressed the induction of GRPs. The pyrimidine ribonucleosides uridine and cytidine also suppressed GRP synthesis, ribose and the purine ribonucleosides guanosine and adenosine suppressed partially. The results, coupled with indirect evidence in the literature, lead to the suggestion that cell ribose 5-phosphate or a related metabolite regulates the expression of GRPs.

Nature of the enzymes that catalyse the cleavage of the N-glycosidic bond of pyrimidine ribonucleosides in some filamentous fungi

Cell-free extracts of nitrate-grown mycelia of Penicillin chrysogenum, Penicillin oxilicum and Fasarium moliforme have the ability to catalyse the cleavage of the N-glycosidic bond of cytidine and uridine optimally at pH 6.2 and 40°. The cleavage of these two nucleosides was effected by a contitutive pyrimidine ribonucleosides hydrolase, a pyrimidine ribonucleosides phosphorylase and a broad spectrum pyrimidine and purine ribonucleosides in extracts of P. chrysogenum, P. oxicalum and Fusarium monoliforme respectively. Deoxyribothymidine was not cleaved by any of these extracts under all the experimental conditioins used.

Synthesis of certain 3‐alkoxy‐1‐β‐D‐ribofuranosylpyrazolo[3,4‐d]pyrimidines structurally related to adenosine, inosine and guanosine

AbstractSeveral 3‐alkoxysubstituted pyrazolo[3,4‐d]pyrimidine ribonucleosides structurally related to adenosine, inosine and guanosine have been prepared by the direct glycosylation of preformed aglycon precursor containing a 3‐alkoxy substituent. Ring closure of 5(3)‐amino‐3(5)‐ethoxypyrazole‐4‐carboxamide (6b) with either formamide or potassium ethyl xanthate gave 3‐ethoxyallopurinol (7b) and 3‐ethoxy‐6‐thioxopyrazolo[3,4‐d]‐pyrimidin‐4(5H,7H)‐one (10), respectively. Methylation of 10 gave the corresponding 6‐methylthio derivative 15. Similar ring annulation of 5(3)‐methoxypyrazole‐4‐carboxamide (6a) with formamide afforded 3‐methoxyallopurinol (7a). Treatment of 5(3)‐amino‐3(5)‐methoxypyrazole‐4‐carbonitrile (5a) with formamidine acetate furnished 4‐amino‐3‐methoxypyrazolo[3,4‐d]pyrimidine (4). High‐temperature glycosylation of 7b with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐D‐ribofuranose in the presence of boron trifluoride etherate gave a 2:1 mixture of N‐1 and N‐2 glycosyl blocked nucleosides 11b and 13b. Deprotection of 11b and 13b with sodium methoxide gave 3‐ethoxy‐1‐β‐D‐ribofuranosylpyrazolo[3,4‐d]pyrimidin‐4(5H)‐one (12b) and the corresponding N‐2 glycosyl isomer 14b, respectively. Similar glycosylation of either 4 or 7a, and subsequent debenzoylation gave exclusively 4‐amino‐3‐methoxy‐1‐β‐D‐ribofuranosylpyrazolo[3,4‐d]pyrimidine (9) and 3‐methoxy‐1‐β‐D‐ribofuranosylpyrazolo[3,4‐d]pyrimidin‐4‐(5H)‐one (12a), respectively. The structural assignment of 12a was made on the basis of single‐crystal X‐ray analysis. Application of this general glycosylation procedure to 15 gave the corresponding N‐1 glycosyl derivative 16 as the sole product, which on debenzoylation afforded 3‐ethoxy‐6‐(methylthio)‐1‐(3‐D‐ribofuranosylpyrazolo[3,4‐d]pyrimidin‐4(5H)‐one (17). Oxidation of 16 and subsequent ammonolysis furnished the guanosine analog 6‐arnino‐3‐ethoxy‐1‐β‐D‐ribofuranosylpyrazolo[3,4‐d]‐pyrimidin‐4(5H)‐one (19). Similarly, starting from 3‐methoxy‐4,6‐bis(methylthio)pyrazolo[3,4‐d]pyrimidine (20), 6‐amino‐3‐methoxy‐1‐β‐D‐ribofuranosylpyrazolo[3,4‐d]pyrimidin‐4(5H)‐one (23) was prepared.

Regioselective phenylcarbamoylation of purine and pyrimidine ribonucleosides through dibutyltin oxide-and tertiary amine-phenyl isocyanate systems

Regioselective phenylcarbamoylation of ribonucleosides through the use of (Bu 2SnO) n -PhNCO systems was revealed to have substantially the same tendency as observed in the reaction through (Bu 3Sn) 2-O-PhNCO, giving the corresponding 3′-phenylcarbamates preferentially over the 2′-phenylcarbamates; the reaction through tertiary amines-PhNCO was, however, proved to give a preponderance of the 2′-phenylcarbamates over the 3′-phenylcarbamates.

Diadenosine 5‘,5“‘-P1, P4-tetraphosphate alpha, beta-phosphorylase from yeast supports nucleoside diphosphate-phosphate exchange.

Homogeneous diadenosine 5',5'''-P1,P4-tetraphosphate alpha, beta-phosphorylase (Ap4A-phosphorylase), the enzyme recently found in yeast (Guranowski, A., and Blanquet, S. (1985) J. Biol. Chem. 260, 3542-3547) catalyzes an exchange reaction between the beta-phosphate of nucleoside diphosphate (NDP) and orthophosphate from the medium (Pi). The common purine and pyrimidine ribonucleoside diphosphates as well as ADP analogs modified either in aglycone, sugar, or at the anhydride bond beta-position are substrates. The Km and rate values for the NDP-Pi exchange reaction were estimated at pH optima. These optima are 6.5 for UDP, 7.0 for ADP or CDP, and 8.0 for GDP. In the presence of 10 mM K2HPO4, 0.1 mM EDTA, and 100 mM Hepes/KOH (pH 7.0), the Km for ADP is 0.7 mM with a rate constant at saturating ADP of 96 s-1. The Km value for orthophosphate is 2 mM. In the NDP-Pi exchange reaction, phosphate can be substituted with arsenate and apparent arsenolysis of NDPs yields corresponding nucleoside monophosphates. The same pH optimum of 6.5 is found for arsenolysis of ADP, GDP, and CDP. Whereas the Ap4A phosphorylase sulfhydryl groups are essential for catalyzing the Ap4A phosphorolysis, the NDP-Pi exchange reactions, and the arsenolysis of NDPs, the divalent metal ions (Mg2+, Mn2+, Ca2+, Co2+, and Cd2+), which had been shown to be essential cofactors of the former reaction, are not required for the two latter ones. Used at concentrations which are optimum for Ap4A phosphorolysis, the cations (particularly Mg2+ and Cd2+) inhibit the NDP-Pi exchange and the arsenolysis of NDPs. Interestingly, the Ap4A phosphorylase exhibits higher specificity for adenosine 5'-phosphosulfate (APS) than for any other NDP tested. The V/Km ratio is almost 5-fold higher with APS than with ADP. However, in the presence of orthophosphate, the APS is irreversibly converted to ADP. Thus, the enzyme displays a property already attributed to ADP-sulfurylase (EC 2.7.7.5), (Grunberg-Manago, M., Del Campillo-Campbell, A., Dondon, L., and Michelson, A. M. (1966) Biochim. Biophys. Acta 123, 1-16; Nicholls, R. G. (1977) Biochem. J. 165, 149-155).

Metabolism of tRNAs in growing cells of Escherichia coli illuminated with near-ultraviolet light.

Abstract— The tRNA metabolism which accompanies illumination of growing E. coli cells has been examined in conditions that led to growth delay. (i) The in vivo formation of the 8–13 link was followed by a fluorimetric procedure and revealed pseudo‐first order kinetics very close to those obtained in vim under the same illumination conditions. The yield of 8–13 link appears to be quantitative (± 10%). Comparison of these kinetics with the radiochromatographic data of Blanchetot et al. (1984) suggests the transient formation during illumination of a new RNase‐T,‐resistant dinucleotide in tRNA distinct from the 8–13 link. (ii) Evidence is provided that under illumination some tRNA molecules lack one or more bases in a specific position in the sequence, thus yielding discrete fragments after aniline treatment. (iii) During the growth lag, uracil incorporation into nucleic acids occurs at an apparent rate between 4–8% of that normally observed during exponential growth. Evidence is provided however that the pyrimidine ribonucleoside triphosphate pools are strongly perturbed after illumination. Comparison of exogenous [3H]uracil incorporation into two strains proficient or deficient in uracil biosynthesis suggests a derepression of the endogenous path after light treatment. In addition, the UTP‐to‐CTP conversion is inhibited. In spite of preferential incorporation of exogenously labelled uracil in tRNA after illumination, a possible pyrimidine base turnover cannot be proved. These data are compatible with tRNA repair (Blanchetot et al., 1984) involving a few tRNA species.

Regioselective protection of carbohydrate derivatives. : Part. 20 Simple, efficient 2'- [formula omitted]-deacylation of fully acylated purine and pyrimidine ribonucleosides through [formula omitted]-butoxide

A simple treatment of fully aroylated purine and pyrimidine ribo-nucleosides with pulverized potassium tert -butoxide in tetrahydrofuran (THF) or dichloromethane under a controlled condition gave a mixture of the corresponding di- O -aroyl derivatives in which 2'-OH derivatives are preponderant over 3'-OH derivatives; 3',5'-di- O -benzoyluridine, N 4, 3', 5'-tribenzoylcytidine, N 4, 3', 5'-tri- o -toluoylcytidine, N 2, 3', 5'-tribenzoylguanosine, and N 2-isobutyryl-3', 5'-di- O -benzoylguanosine were obtained crystalline in 80%, 78%, 72%, 67%, and 65% yields, respectively.

Synthesis of 5-chloroformycin A, 5-chloro-2'-deoxyformycin A and certain related 5,7-disubstituted 3-beta-D-ribofuranosylpyrazolo[4,3-d] pyrimidines from formycin A.

A facile synthesis of 7-amino-5-chloro-3-beta-D-ribofuranosylpyrazolo [4,3-d]pyrimidine (5-chloroformycin A, 6), 7-amino-5-chloro-3-(2-deoxy-beta-D-erythro-pentofuranosyl) pyrazolo [4,3-d]-pyrimidine (5-chloro-2'-deoxyformycin A, 13) and certain related 5,7-disubstituted pyrazolo[4,3-d]pyrimidine ribonucleosides is described starting with formycin A. Thiation of tri-O-acetyloxoformycin B (4b) with phosphorus pentasulfide, followed 3-beta-D-ribofuranosyl-7-thioxopyrazolo[4,3-d] pyrimidin-5(1H,4H,6H)-one (3b) in excellent yield. Chlorination of 4b with either phosphorus oxychloride or phenyl phosphonicdichloride furnished the key intermediate 5,7-dichloro-3-(2,3, 5-tri-O-acetyl-beta-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (5a), which on deacetylation afforded 5,7-dichloro-3-beta-D-ribofuranosylpyrazolo [4,3-d]pyrimidine (5b). Ammonolysis of 5a with liquid ammonia gave 6, whereas with MeOH/NH3, a mixture of 6 and 7-methoxy-5-chloro-3-beta-D-ribofuranosylpyrazolo[4,3-d]pyrimidine (7) was obtained. Reaction of 6 with lithium azide and subsequent hydrogenation afforded 5-aminoformycin A (10). Treatment of 5a with thiourea gave 5-chloro-3-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl) pyrazolo[4,3-d]pyrimidine-7(1H,6H)-thione (8a), which on further reaction with sodium hydrosulfide furnished 3-beta-D-ribofuranosylpyrazolo [4,3-d]pyrimidine-5,7(1H,4H,6H)-dithione (11). The four-step deoxygenation procedure using phenoxythiocarbonylation of the 2'-hydroxy group of the 3', 5'-protected 6 gave 5-chloro-2'-deoxyformycin A (13).

Re-utilization of pyrimidine nucleotides during rat liver regeneration

The changes in the specific radioactivities of the pool of total acid-soluble uridine nucleotides and of uridine and cytidine components of total cellular and nuclear RNA were monitored in regenerating rat liver for 12 days after partial hepatectomy. Evidence is presented for the re-utilization of pyrimidine nucleotides derived from cytoplasmic RNA degradation for the synthesis of new RNA. The extent of recycling was assessed and the true rate of rRNA turnover determined more accurately. The reutilization of the uridine components of RNA was 7.0%/day during the proliferative and 3.2%/day during the post-proliferative phase, whereas that of the cytidine nucleotides was more pronounced (9.6%/day and 18.1%/day respectively). The results reveal the existence of partial compartmentalization of pyrimidine ribonucleoside triphosphate pools in the nucleus and cytoplasm of rat liver cells.

ChemInform Abstract: SYNTHESIS AND BIOLOGICAL ACTIVITY OF CERTAIN 3,4‐DISUBSTITUTED PYRAZOLO(3,4‐D)PYRIMIDINE NUCLEOSIDES

AbstractPyrazolopyrimidinnucleoside (I) werden dargestellt und auf Antivirus‐ und Antitumor‐Wirkung untersucht.

Partial protection of carbohydrate derivatives. part 18. simple, preparative procedure for 5'- [formula omitted]-acylribonucleosides; highly regioselective [formula omitted]-deacylation at 2' and 3' positions of fully acylated purine and pyrimidine ribonucleoside through sodium methoxide-thf system

A treatment of fully acylated purine and pyrimidine ribonucleosides with a small excess amount of sodium methoxide in THF at room temperature gave the corresponding 5'-acylates in excellent yields; N -acyl groups on the nucleic acid base moieties of adenosine and cytidine in addition to guanosine derivatives satisfactorily survived under the conditions used.

Influence of the stationary phase on the retention characteristics of purine and pyrimidine bases, ribonucleosides and deoxyribonucleosides in reversed-phase high-performance liquid chromatography

Abstract The influence of the chain length of alkylsilica stationary phases on the selectivity of the separation of purine and pyrimidine bases and nucleosides is investigated, and the reproducibility of the retention when applying a constant gradient program with different packing materials is discussed. The use of different alkylsilica stationary phases leads to appreciable changes in the retention, but peak identification on the basis of retention data remains possible for most of the compounds when an appropriate internal standardization method is employed. The investigations were performed by applying a gradient program which allows the separation of up to 20 physiologically important purine and pyrimidine bases, ribonucleosides and 2′-deoxyribonucleosides on alkylsilica adsorbents.

Uridylate-trapping sugar analogs in combination with inhibitors of uridylate synthesis de novo and 5-fluorouridine

The combination of 3 types of antipyrimidines was studied in AS-30D hepatoma cells in suspension culture and in the rat in vivo. 1. 1.|Callulear UTP and CTP pools can be depleted most effectively by combining an inhibitor of de novo UMP synthesis with sugar analogs diverting UMP to UDP-sugar analogs. The following UMP-trapping sugar analogs were employed: d-galactosamine, d-galactosone, d-glucosome, and d-glucosamine. These d-galactose and d-glucose analogs intensified the depletion of UTP and CTP pools induced by the following inhibitors of de novo UMP synthesis: acivicin, PALA, palachol, pyrazofurin, and 6-azauridine. 2. 2.|The sugar analogs, in the absence of inhibitors of the de novo pathway, enhanced the rate of de novo UMP synthesis several-fold, as indicated by incorporation of 14CO 2 into intermediates and the products of the pathway and by the expansion of the acid-soluble uracil nucleotide pool. 3. 3.|Reduction of UTP and CTP contents to less than 5 and 15% of control, respectively, by d-galactosamine and PALA resulted in a decrease of the rate of RNA synthesis to 19% of control as calculated from the changes in specific activities of [ 14C]CTP and of [ 14C]cytidine in RNA after labeling with [ 14C]uridine. [cating that pyrimidine nucleoside excretion is regulated by pyrimidine nucleotide levels, possibly by UTP and CTP regulation of uridine kinase. 4. 5.|Determinaton of the rates of de novo pyrimidine synthesis, of the formation of RNA pyrimidines, and of pyrimidine nucleoside excreton indicates that de novo synthesis provides only about 67% of the pyrimidines required for the consuming processes. The difference, as well as the dilution of labeled pyrimidine nucleotide pools under conditions of a blocked de novo pathway, suggests a considerable salvage of pyrimidine nucleosides derived from RNA. This salvage of pyrimidines may be intracellular and/or by an excretion and re-uptake process. 5. 6.|Depletion of UTP and CTP pools, induced in hepatoma cells by d-galactosamine and 6-azauridine, leads to growth inhibition in suspension culture; this inhibition becomes irreversible in an increasing percentage of cells, killing all cells after 20 hr of UTP deficiency. 6. 7.|The enhanced uptake of 5-fluorouridine by UTP-deficient cells was associated with an increase of FUMP incorporation into RNA up to 4-fold and with stronger inhibition of cell growth. The amounts of FUDP-sugars formed from 5-fluorouridine in hepatoma cells were smaller than the amounts of UDP-sugars formed from uridine. All the FUDP-sugars served as substrates i vitro of the respective enzymes of UDP-sugar metablism. 7. 8.|Combination of UMP-trapping sugar analogs with an inhibitor of de novo UMP synthesis and followed by a pyrimidine ribonucleoside analog such as 5-fluorouridine may improve the tissue selectivity and the effectiveness of tumor chemotherapy with antipyrimidines.

Synthesis and biological activity of certain 3,4-disubstituted pyrazolo[3,4-d]pyrimidine nucleosides.

A number of 3,4-disubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides were synthesized and tested for their biological activity. Glycosylation of persilylated as well as nonsilylated 3-bromoallopurinol with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose (4) provided the key intermediate 3-bromo-1-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)-pyrazolo[3,4-d] pyrimidin-4(5H)-one (5a). Similar glycosylations of 3-cyanoallopurinol and 3-(methylthio)allopurinol furnished the corresponding protected N-1 glycosyl derivatives (5b and 5c). Debenzoylation of these nucleosides (5a-c) gave the corresponding 3-bromo-, 3-cyano-, and 3-(methylthio)allopurinol nucleosides (6a-c). The site of glycosylation and anomeric configuration of 6a and 6c were assigned on the basis of spectral studies as well as conversion to allopurinol ribonucleoside, whereas the structural assignment of 6b was made by single-crystal X-ray analysis. Conventional functional group transformation of 5a and 5b provided a number of novel 3-substituted allopurinol nucleosides, which included 10a and 18a-d. Glycosylation of 4-amino-3-bromopyrazolo[3,4-d]pyrimidine (14) with 4 and subsequent debenzoylation gave 3-bromo-4-aminopyrazolo[3,4-d]pyrimidine ribonucleoside (13a) from which 3,4-diamino-1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidine (13b) was obtained by amination. Thiation of 5b, followed by deblocking, gave 3-cyanothiopurinol ribonucleoside (20). All of these compounds were tested in vitro against certain viruses, tumor cells, and the parasite Leishmania tropica. Among the 3-substituted allopurinol nucleosides, 18b and 18c showed significant activity against Para 3 virus and were found to be potent inhibitors of growth of L1210 and P388 leukemia. Compound 20 exhibited the most significant broad-spectrum in vitro antiviral and antitumor activity. 3-Bromoallopurinol ribonucleoside (6a) was found to be more active than allopurinol ribonucleoside against Leishmania tropica within human macrophages in vitro.

ChemInform Abstract: Pyrazolo[3,4»d]pyrimidine Ribonucleosides as Anticoccidials. Part 3. Synthesis and Activity of Some Nucleosides of 4‐[(Arylalkenyl)thio]pyrazolo[3,4‐d]pyrimidines.

AbstractDurch Alkylierung entsprechender Mercaptopyrimidine entstehen die Verbindungen (I), die gegen Eimeria tenella in vivo getestet werden.

Purine and pyrimidine base and nucleoside concentrations in human cerebrospinal fluid and plasma.

Purine and pyrimidine base and nucleoside levels were determined in adult human lumbar (CSF) and plasma by reversed-phase high performance liquid chromatography (HPLC). Guanine, thymine, cytosine and uracil were not detectable (less than 0.1 microM) in human CSF or plasma. Adenine was detectable in plasma (0.3 microM) but was not found in CSF (less than 0.2 microM). Hypoxanthine and xanthine levels in CSF were each approximately 2.5 microM. Plasma levels of hypoxanthine and xanthine were considerably lower (0.4-0.6 microM). Purine and pyrimidine ribonucleosides in human CSF were less than or equal to 0.2 microM with the exception of uridine which was present at concentrations of 2-3 microM. Although low concentrations of thymidine and deoxyuridine (0.2 microM) were present in human plasma, purine and pyrimidine deoxyribonucleosides were less than 0.1 microM in human lumbar CSF.

Pyrazolo[3,4-d]pyrimidine ribonucleosides as anticoccidials. 3. Synthesis and activity of some nucleosides of 4-[(arylalkenyl)thio]pyrazolo[3,4-d]pyrimidines.

Ribonucleosides of 4-(alkylthio)-1H-pyrazolo[3,4-d]pyrimidines have been shown to be useful anticoccidial agents [Krenitsky, T. A.; Rideout, J. L.; Koszalka, G. W.; Inmon, R. B.; Chao, E. Y.; Elion, G. B.; Latter, V. S.; Williams, R. B. J. Med. Chem. 1982, 25, 32. Rideout, J. L.; Krenitsky, T. A.; Elion, G. B. U.S. Patent 4299 283, 1981]. In that study, the unsaturated 4-allylthio and 4-crotylthio derivatives (19 and 20) were shown to be more active in vivo against Eimeria tenella than their saturated congeners; therefore, some unsaturated (arylalkyl)thio derivatives were synthesized and investigated as anticoccidial agents. The novel compounds in this study (2 to 18) were prepared by the alkylation of 4-mercapto-1-beta-D-ribofuranosyl-1H-pyrazolo[3,4-d]pyrimidine (1), which was prepared by an enzymatic method. The (E)-4-cinnamylthio derivative (2) and the 5'-monophosphate (18) were the most active compounds against E. tenella in vivo. None of the analogues with substituents in the aryl moiety (3 to 13) was more active than 2 in vivo. The geometry about the double bond was important, since the (Z)-4-cinnamylthio derivative (14) was inactive both in vitro and in vivo. The 4-(3-phenylpropynyl)thio and 4-(5-phenyl-2,4-pentadienyl)thio derivatives (15 and 16) were at least as active as 2 in vitro; however, they were less active than 2 in vivo. Compound 2 was effective in vivo against E. tenella, E. necatrix, E. maxima, and E. brunetti; these species of Eimeria were controlled when 2 was given in the diet at levels upt to 100 ppm. Infections in vivo due to E. acervulina were controlled by 2 only at about 800 ppm. The broad spectrum of anticoccidial activity shown by 2 represents a significant improvement over the activities reported for related compounds [Krenitsky, T. A.; Rideout, J. L.; Koszalka, G. W.; Inmon, R. B.; Chao, E. Y.; Elion, G. B.; Latter, V. S.; Williams, R. B. J. Med. Chem. 1982, 25, 32].

Purines as 'hyper-repressors' of glucose transport. A role for phosphoribosyl diphosphate.

Under selected conditions the rate of glucose transport and the intracellular phosphoribosyl diphosphate (PPRibP) concentrations of chick-embryo fibroblasts are inversely correlated. This relationship holds when cells are incubated with mannose, fructose, xylose or various concentrations of glucose. The metabolic inhibitors 2,4-dinitrophenol, rotenone and Methylene Blue increased glucose transport and decreased PPRibP. The addition of any pyrimidine or purine base or ribonucleoside dramatically depleted PPRibP pools, regardless of the carbon source. Addition of guanine (10 microM) or hypoxanthine (100 microM) decreased transport in glucose-grown chick cells to barely detectable values, but did not affect increases observed in cells depressed by substitution of xylose for glucose. Guanosine, inosine and the purine analogues 6-thioguanine, 6-thioguanosine, 8-azaguanine and 6-methylmercaptopurine riboside sharply decreased transport in glucose-grown cells and blocked the increase in transport resulting from the replacement of glucose by fructose or xylose in the culture medium.

A facile radio-isotopic assay for phosphoribomutase activity in human red blood cells

The serendipitous discovery of complete adenosine deaminase deficiency in some patients with autosomal recessive inherited severe combined immunodeficiency [l] suggested that other enzymatic deficiencies leading to impaired breakdown of nucleosides might produce immunodeficiency; this was rapidly confirmed by the discovery of purine nucleoside phosphorylase deficiency, which is associated with severe T-cell dysfunction [2]. In mammals, the phosphorolytic degradation of purine and pyrimidine ribonucleosides produces a base and ribose1 -phosphate (R, P). R, P is subsequently isomerized into R,P by a phosphoribomutase activity. Phosphoribomutase thus realizes a link between purine and pyrimidine, and carbohydrate metabolism; it prevents R,P accumulation, and should be considered as part of the catabolism pathways of purine and pyrimidine nucleosides. Phosphoribomutase activity was detected in human red blood cells by Guarino and Sable in 1955 [3], using a calorimetric method. To our knowledge, the enzyme has not been studied further in human tissues, and has not been assayed by the laboratories working on purine and pyrimidine metabolism, most probably because of the absence of an easy method for determination of this enzymatic activity. Here we describe a radio-isotopic assay and some properties of the phosphoribomutase of the human erythrocyte, which is the tissue most often used for the detection of inborn errors of purine or pyrimidine metabolism.