SVIBOR - Papers quoted in CC - project code: 1-07-220

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Papers quoted in Current Contents on project 1-07-220

Quoted papers: 12
Other papers: 8
Total: 20

Title: Synthesis and Structure of Dehydro-4-iminoallantoin and Its Covalent Adducts

Authors:: Popović, Tomislav; Sokolić, Lea (70913); Modrić, Nevenka (126693); Palković, Antun (34733); Poje, Mirko (37773)

Journal: Tetrahedron
Number: 2
ISSN: 0040-4020
Volume: 47
Year: 1991
Pages: from 317 to 322
Number of references: 18
Language: engleski
Summary: Representations of two consecutive products of the Denicke reaction were shown to be incorrect. Oxidation of uric acid (1a) by ferricyanide in aqueous ammonia gives 5-amino-4-iminoallantoin (4) and 1,5-diamino-3,7-dioxo-2,4,6,8-tetraazabicyclo(3.3.0)octane (5a), while methylated uric acids 1b-g afford only the corresponding end-products 5. The key dehydro-4-iminoallantoin (6) arose on exposure of the primary adduct 4 to dilute acetic acid; a direct route to (6) was provided by oxidation of 4-iminoallantoin (2) with iodine. Both dehydroallantoin (8) and its 4-imino analogue(6) form covalent adducts (e.g., with MeOH) at the 5-position. A brief rationale which focusses upon the stepwise nature and regiochemical course of the reaction is presented.
Keywords: purine, oxidation, ring-transformation, rearrangement, 5-amino-4-iminoallantoin, Denicke reaction, structural revision, ferricyanide oxidation, covalent adducts, 4-iminoallantoin, 1,5-diamino-3,7-dioxo-2,4,6,8-tetraazabicyclo(3.3.0)octane, dehydroallantoin, dehydro-4-iminoallantoin, uric acid

Title: Regiochemical Course of Chemical and Enzymic Uricolysis to Allantoin. A Non-Degradative 13C-NMR Evidence

Authors:: Sokolić, Lea (70913); Modrić, Nevenka (126693); Poje, Mirko (37773)

Journal: Tetrahedron Letters
Number: 50
ISSN: 0040-4039
Volume: 32
Year: 1991
Pages: from 7477 to 7480
Number of references: 25
Language: engleski
Summary: Use of 8-13C-urate (1b) in combination with 13C-NMR method provided unequivocal evidence for the formation of 2-13C-allantoin (4b) in the course of chemical, uricase-, or peroxidase-mediated oxidations.
Keywords: purine, oxidation, ring-transformation, allantoin, 13C-labelling, NMR, iodine, lead(IV)oxide, peroxidase, uricase, regiochemistry, uric acid, uricolysis

Title: Tracing and Identification of Uricase Reaction Intermediates. A Direct13C-NMR/Isotope-Labelling Evidence

Authors:: Modrić, Nevenka (126693); Derome, Andrew E.; Ashcroft, Stephen J. H.; Poje, Mirko (37773)

Journal: Tetrahedron Letters
Number: 44
ISSN: 0040-4039
Volume: 33
Year: 1992
Pages: from 6691 to 6694
Number of references: 25
Language: engleski
Summary: The 13C-NMR spectra are characteristic and provide a convenient method to chart the pathway of uricase-catalysed oxidation of 5-13C-urate (1) to 4-13C-allantoin (5); 5-hydroxy-5-13C-isouricacid (2), its ring-opened derivative 3, and 4-13C-allantoin-5-carboxylate (4) were identified as consecutive intermediates in D2O/phosphate buffer (pD 7.2).
Keywords: purine, oxidation, ring-transformation, rearrangement, allantoin, 5-hydroxyisouric acid, intermediates, NMR/13C-labelling, uric acid, uricase, uricolysis

Title: Absolute Stereochemistry of Alloxanic Acid. A Configurational Relay for Uricase Reaction

Authors:: Modrić, Nevenka (126693); Poje, Mirko (37773); Watkin, David J.; Edwards, Alison J.

Journal: Tetrahedron Letters
Number: 29
ISSN: 0040-4039
Volume: 34
Year: 1993
Pages: from 4679 to 4682
Number of references: 19
Language: engleski
Summary: Alloxanic Acid (3) was resolved by means of brucine and converted into its enantiomorphic esters (8) and amides (9); ethyl (-)-alloxanate whose absolute configuration was established by X-ray analysis served as configurational standard for the correlation of (+)-(R)-(3) and its precursor, (-)-(S)-5-hydroxyisourate (2), the key uricolytic intermediate.
Keywords: allantoin, absolute configuration, stereochemistry, alloxanic acid, ethyl (-)-(S)-alloxanate, resolution, uric acid, purine, oxidation, ring-transformation, uricase, uricolysis, X-ray analysis

Title: New Synthesis of Uroxanic Acid via a Propellane Type Model of Its Uricolytic Precursor

Authors:: Poje, Nevenka; Poje, Mirko (37773)

Journal: Bioorganic and Medicinal Chemistry Letters
ISSN: 0960-894X
Volume: 5
Year: 1995
Pages: from in to press
Number of references: 23
Language: engleski
Summary: 5-Chloro-1,3-dimethyl-5,7-dihydro-3H-purine-2,6,8-trione (8) reacted with urea in boiling acetic acid to give 2,4,7,9,10,12-hexaazatricycloŠ4.3.3.01,6Ćdodecan-3,5,8,11-tetraone(9), which underwent a facile base-catalysed hydrolysis, providing a model for biogenesis of uroxanate (3).
Keywords: purine, oxidation, rearrangement, ring-transformation, hexaaza(4.3.3)propellane, orthoamide, uricolysis, uroxanic acid, allantoin, biogenetically-modelled synthesis, uric acid

Title: The Structure of a C5H4N4O4 species Trapped by Silylation in Peroxidase-Mediated Uricolysis

Authors:: Modrić, Nevenka (126693); Poje, Mirko (37773)

Journal: Bioorganic and Medicinal Chemistry Letters
Number: 14
ISSN: 0960-894X
Volume: 4
Year: 1994
Pages: from 1685 to 1686
Number of references: 20
Language: engleski
Summary: Evidence for the species trapped by trimethylsilylation in peroxidase mediated oxidation of urate (1) having the tetrakis(trimethylsilyl)spirodihydantoin (4b) structure is provided by its hydrolysis, reaction with diazomethane, and actual isolation and identification of tetramethylspirodihydantoin (4c).
Keywords: purine, oxidation, ring-transformation, rearrangement, peroxidase, uricolysis, uric acid, trimethylsilylation, ring-contraction, tetrakis(trimethysilyl)spirodihydantoin, tetramethylspirodihydantoin

Title: Studies on Covalent Adducts of Dehydrouric Acid

Authors:: Modrić, Nevenka (126693); Palković, Antun (34733); Perina, Ivo (72500); Poje, Mirko (37773)

Journal: Croatica Chemica Acta
Number: 3
ISSN: 0011-1643
Volume: 67
Year: 1994
Pages: from 347 to 360
Number of references: 38
Language: engleski
Summary: The structure of 5-chloro and 5-alkoxy-5,7-dihydro-3H-purine-2,4,6-triones (6 and 7-9) has been corroborated by their spectral properties and X-ray crystallography. The stereochemical model (R)-10 of the key uricolytic intermediate was prepared using menthol as chiral auxiliary. In acidic solutions, depending on the N-substitution, the ring cleavage occurred either at the 4,9-bond 6b --> 13 (R1 = Me) or at the 3,4-bond 6c --> 14 (R1 = H). Opening of the 1,6-bond is the dominant process under alkaline conditions. Decarboxylative rearrangement into 1,3-dimethylallantoin (15) was specific for N(7)-unsubstituted derivatives. The evidence for intermediacy of the bicyclol tautomeric form was supplied by isolation of 1-menthoxy-2,4-dimethyl-3,7-dioxo-2,4,6,8-tetraazabicycloŠ3.3.0Ćoctane (16); fragmentation of 10 into 5-menthoxy-imidazolidin-2,4-dione (17) also takes place under forcing conditions. Conversely, the allantoin rearrangement was not encountered with the R7 = Me cases; 7d underwent the pyrimidine ring fragmentation to give 5-methoxy-1-methyl-4-methylimino-imidazolidine-2-one (18) or 5-carboxamido-5-methoxy-1-methyl-4-methylimino-imidazolidine-2-one(19). A possible mechanism for these ring transformation reactions is discussed.
Keywords: purine, oxidation, 5-alkoxy-5,7-dihydro-3H-purine-2,6,8-triones, ring-opening, solvolysis, stereochemistry, uricolysis, chiral auxiliary, menthol, 1,3-dimethylallantoin, 1-menthoxy-2,4-dimethyl-3,7-dioxo-2,4,6,8-tetraazabicyclo(3.3.0)oc tane, ring-chain tautomerism, mechanism, ring-transformation

Title: cis-1,5-Diamino-3,7-dioxo-2,4,6,8-tetraazabicyclo(3.3.0)octane

Authors:: Modrić, Nevenka (126693); Poje, Mirko (37773); Vicković, Ivan

Journal: Acta Crystallographica
ISSN: 0108-2701
Volume: C51
Year: 1995
Pages: from in to press
Number of references: 5
Language: engleski
Summary: The title compound, cis-1,5-diamino-3,7-dioxo-2,4,6,8-tetraazabicycloŠ3.3.0Ćoctane (1), represents a virtually unknown vicinal orthoamide array, formally derivable from oxalic acid. The cis-fused imidazolidinone rings adopt a flattened envelope conformation. Hydrogen atoms of nearly eclipsed vicinal diamine ŠN1-C1-C5-N5 -9.5(3)řĆ are oriented inward ŠH1a...H5a = 2.44(4)A and H1b...H5b = 2.49(4)AĆ.
Keywords: purine, ring-transformation, rearrangement, uricolysis, uric acid, oxidation, ferricyanide, amino-adduct, dehydroallantoin, vic-orthoamide

Title: cis-4,5-Ethylenedioxy-1,3-dimethyl-tetrahydropurine-2,6,8-trione

Authors:: Poje, Nevenka; Poje, Mirko (37773); Vicković, Ivan

Journal: Acta Crystallographica
ISSN: 0108-2701
Volume: C51
Year: 1995
Pages: from in to press
Number of references: 7
Language: engleski
Summary: The title compound (1) adopts a distinct ring-twisted conformation defined by nearly orthogonal bridgehead torsion angles ŠC16-C15-C14-N19 = -90.1(2) and C26-C25-C24-N29 = -87.8(2)řĆ; the antiperiplanar array ŠC17-O14-C14-N19 = -158.0(2) and C27-O24-C24-N29 = -158.3(2)řĆ does not allow stereoelectronically controlled ring-opening at the 4,9-bond.
Keywords: dioxatetraaza(4.4.3)propellane, conformation, stereoelectronic control, ring-transformation, purine, oxidation, uricolysis, rearrangement, uric acid

Title: 8a-Methoxy-1,7-dimethyl-dihydro-imidazo(1,5-a)-1,3,5-triazine-2,4,6,8-tetra one

Authors:: Modrić, Nevenka (126693); Vicković, Ivan; Poje, Mirko (37773)

Journal: Zeitschrift fuer Kristallographie
ISSN: 0044-2968
Volume: 210
Year: 1995
Pages: from in to press
Number of references: 9
Language: engleski
Summary: The classic formula for theobromuric acid Š1,2Ć was revised; the correct formula represents a virtually unknown acid aminal array Š3Ć. The crystal structure of its derived methyl ester aminal, the methyl theobromurate, 8a-methoxy-1,7-dimethyl-dihydro-imidazoŠ1,5-aĆ-1,3,5-triazine-2,4,6,8-tetra one, corroborates the new assignment based on chemical and spectroscopic evidence. The angular substituent is oriented antiperiplanar to the ring carbonyl C8, torsion angle (C8-C8a-O1-C9) = -172.9(1)ř. The imide fragment O2-C2-N3-H3 is involved in dimeric association via a pair of hydrogen bonds: H3...O2 = 2.10(5)A, N3...O2= 2.895(2)A, N3-H3...O2= 154(4)ř (2-x,-y,1-z).
Keywords: purine, ring-transformation, oxidation, rearrangement, theobromuric acid, acid aminal, imidazo(1,5-a)s-triazine, structural revision

Title: Crystal Structure of cis-4,5-dimethoxy-1,3-dimethyl-tetrahydropurine-2,6,8-trione

Authors:: Poje, Nevenka; Poje, Mirko (37773); Vicković, Ivan

Journal: Zeitschrift fuer Kristallographie
ISSN: 0044-2968
Volume: 210
Year: 1995
Pages: from in to press
Number of references: 7
Language: engleski
Summary: Two independent molecules of the title compound adopt the ring-twisted conformation (b) Š3Ć, defined by roughly orthogonal bridgehead torsion angles (N13-C14-C15-N17 = 95.1(3) and N23-C24-C25-N27 = 97.1(3)ř). Stereoelectronically controlled ring-opening at the N3-C4 bond in the course of acidic hydrolysis thus occurs at the acid aminal stage of the multistep reaction Š4Ć via a conformational change to the proper ring-twisted conformer (a) Š2Ć.
Keywords: dihydro-uric acid, ester aminal, conformation, stereoelectronic control, ring-tranformations, purine, oxidation, uricolysis, rearrangement, uric acid

Title: Structural Revision of Uric Acid Glycol Half-Ethers

Authors:: Poje, Nevenka; Poje, Mirko (37773)

Journal: Tetrahedron Letters
ISSN: 0040-4039
Volume: 36
Year: 1995
Pages: from in to press
Number of references: 32
Language: engleski
Summary: The classic formulae of uric acid glycol half-ethers (2) are revised; compounds with R1=H are shown to have 3,4-ring-opened structures 4 while those with R1=R3=Me,R7=H are 1-carbamido-5-methoxy-alloxanic acid amides (5), derived by a further rearrangement, possibly involving the 2,3a,5-triazapentalene related transition state.
Keywords: 4,5-dialkoxy-tetrahydro-purine-2,6,8-trione, 4,5-dialkoxy-dihydro-uric acid, solvolysis, ring-transformation, purine, oxidation, rearrangement, uric acid, uricolysis, alloxanic acid, 4-methoxy-2,5-dioxo-4-imidazolidinecarboxyureide, 1-carbamido-4-methoxy-2,5-dioxo-4-imidazolidinecarboxamide


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