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NEW 2-(2'-PHENYL-9'-AZAPURIN-6'-YLAMINO)-CARBOXYLIC ACID METHYLESTERS AS LIGANDS FOR A1 ADENOSINE RECEPTORS
No full textSynthesis of a series of new 2-phenyl-9-benzyl-8-azaadenines bearing on N6 an alkyl or aralkyl chain having a carbonyloxymethyl group on the carbon bound to N6 were reported. The ester group could assure to the molecule a better water-solubility than the 8-azaadenines 2, 6 and 9 substituted with lipophilic groups synthesised in the past. Compounds synthesised demonstrated only little capability of binding A1 adenosine receptors
NEW 1,2,3-TRIAZOLO[4,5-E]1,2,3-TRIAZOLO[4,3-C]PYRIMIDINE DERIVATIVES.II
No full textThe 7-chloro-3-(2-chlorobenzyl)- and 7-chloro-3-(2-fluorobenzyl)-1,2,3-triazolo[4,5-d]pyrimidines (1 and 4), by nucleophilic replacement with some hydrazides, gave the corresponding 7-hydrazidoderivatives (2a-e and 5a-e). These, by heating in Dowtherm, underwent an intramolecular cyclization to form the new tricyclic 7-substituted-3-(2-chlorobenzyl)- and 3-(2-fluorobenzyl)-1,2,3-triazolo[4,5-e]1,2,4-triazolo[4,3-c]pyrimidines (3a-d and 6a-d). The 7-hydrazino-3-(2-chlorobenzyl)- and 7-hydrazino-3-(2-fluorobenzyl)-triazolo-pyrimidines (9a and 9b) were also prepared via the corresponding mercapto (7a and 7b) and thiomethyl (8a and 8b) derivatives
2-ALKYLOXYALKYLTHIOHYPOXANTHINES AS NEW POTENT INHIBITORS OF XANTHINE OXIDASE
No full textThe title compounds were prepared and tested as xanthine oxidase (XO) inhibitors. Results evidenced that potency was related to the position of the oxygen atom in the 2-linear chain and that it grew with distance from the sulfur atom until it became equipotent to 2-n-hexylthiohypoxanthine. Enzymatic oxidation on C(2) occurred in the 8-alkylthiohypoxanthines. On the contrary, oxidation on C(8) did not occur in the 2-alkythioderivatives, demonstrating that the chain forced these molecules to form a complex with molybdenum(VI) involving only the N(3) and N(9) nitrogen atoms
New C(2)-substituted 8-alkylsulfanyl-9-phenylmethyl-hypoxanthines. III
No full textTitle compounds were obtained starting from the key imidazole intermediate, 5-amino-1-phenylmethyl-2-mercapto-1H-imidazole-4-carboxylic acid amide 5, readily derived from the base catalyzed rearrangement of a thiazole, 5-amino-2-phenylmethylaminothiazole-4-carboxylic acid amide 4. Alkylation of the thiol function on 5 with phenylmethyl and allylic chlorides gave compounds 6 and 7 respectively. Cyclization of 6 with a variety of esters afforded 8-phenylmethylthiohypoxanthines, 8-11. Similarly, 7 was cyclized to 8-allylthiohypoxanthines, 20-21. Compound 5 was also cyclized, but formed 8-mercaptohypoxanthines, 22-24. Alkylation of 8-mercaptohypoxanthines afforded 8-alkylthiohypoxanthines, 8, 9, 25 and 26 (see Scheme 2). Chlorination of 9-11 afforded 16-18; adenine 19 was derived from 16. Oxidation of hypoxanthines 8-11 with m-chloroperbenzoic acid gave the corresponding 8-phenylmethylsulfonyl derivatives 12–15. These derivatives proved resistant to nucleophilic displacement reactions with primary amines
Preparation of New N6,9-disubstituted-2-phenyladenines and corresèponding 8-azaadenines. A feasibility study for application to solid-phase synthesis
No full textA suitably substituted pyrimidine 1 was converted to a number of title compounds. Nucleophilic substitution involving the chlorine atoms in 1 by treatment with phenylmethanethiol yielded 2 or 3, depending on the reaction temperature. Treatment of 3 with an amine afforded 6-phenylmethanesulfanyl-N4-substituted-2-phenyl-pyrimidine-4,5-diamines 4-7. These pyrimidines were converted into 2-phenylpurines 8-11 and 2-phenyl-8-azapurines 12-14, by treatment with triethyl orthoformate in the presence of hydrochloric acid (or acetic anhydride), or with potassium nitrite and acetic acid respectively. The thioether function on C(6) was then converted into a sulfonyl group by oxidation with m-chloroperoxybenzoic acid affording purines 15-18 and their 8-azaanalogs 19-21; these compounds, as crude products, were treated with an amine to yield the corresponding adenines 22-25 or 8-azaadenines 26-31. All reactions were performed under conditions compatible with the possible use of a thiomethyl resin in place of phenylmethanethiol to bind the pyrimidine ring of 1 to a solid phase
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
NEW N6-SUBSTITUTED-8-ALKYL-2-PHENYLMETHYLSULPHANYLADENINES. II
No full textTitle compounds bearing substituents on C(2), C(6) and C(8) were prepared from a newly synthesized pyrimidine derivative 11. The new pyrimidine 11 was generated from compound 2 through two different synthetic schemes. In one pathway, compound 2 was nitrosated, reduced and alkylated to produce compounds 9, 10 and 11 respectively (Scheme). In an alternate route using compound 2 as the starting material, a coupling reaction using the diazonium salt derived from p-methylaniline afforded the azo derivative 7, which was subsequently alkylated and reductively cleaved to form compounds 8 and 11 respectively (See Scheme). Compound 11 was annulated to the corresponding hypoxanthine derivatives 12-14; compounds 12 and 13 were chlorinated with phosphorus oxychloride, then reacted with amines to yield compound 17 and 20 respectively. Compounds 21, 22 and 23 were obtained by oxidation of the corresponding sulfide as depicted in Scheme. Alkylation of the thiol function of 1 gave a mixture of 3 and 4. Compound 3 was chlorinated to 5. Nitration of 5 resulted in electrophilic aromatic substitution of the aryl ring and concomitant oxidation of the sulfide to the sulfoxide, producing 6
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