First and second coordination spheres in divalent metal compounds containing pyridine and 4,6-dimethyl-1,2,3-triazolo[4,5-d]pyrimidin-5,7-dione

The interaction in aqueous media of 4,6-dimethyl-1,2,3-triazolo[4,5-d]pyrimidin-5,7-dione (1,3-dimethyl-8-azaxanthine, Hdmax) with salts of divalent Mn, Co, Ni, Cu, Zn and Cd in the presence of an excess of pyridine (py) leads to the formation of crystalline solids, the structures of which have been solved by single crystal X-ray diffraction. The solids containing Mn, Co, Zn and Cd are isostructural, presenting a formulation trans-[M(H₂O)₄(py)₂](dmax)₂, with the heterocycle in the anionic form and not directly linked to the metal atom. The H-bond network of these complexes include a tape superstructure topologically identical to that present in the previously reported hexa-aqua salts of the dmax⁻ anion, which may be regarded as a case of molecular recognition between dmax⁻ and the square planar [M(H₂O)₄] subunit. On the other hand, for Ni and Cu the triazolopyrimidine ligand is directly coordinated to the metal through the external imidazole nitrogen atom (N2) generating the compounds [M(dmax)₂(H₂O)₂(py)₂] · 2H₂O, which display a less tight H-bonding network.     

Amino Acid Derivatives, VI [1]: Synthesis, Antiviral, and Antimicrobial Evaluation of α-Amino Acid Esters Bearing a 1,2,3-Triazolo[4,5-d]pyrimidinedione Side Chain

Summary. A series of peptide and dipeptide derivatives conjugated with a 1,2,3-triazolo[4,5-d]pyrimidinedione residue were synthesized. The new compounds were evaluated in vitro for cytotoxicity against HAV-27 and HSV-1 and showed moderate activity. The prepared compounds were tested for antimicrobial activity against four different bacterial species, and they displayed different degrees of antibacterial activities or inhibitory actions.     

Copper(II) complexes with 1,2,4-triazolo[1,5-a] pyrimidine and its 5,7-dimethyl derivative

Several Cu(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidine (tp) and its 5,7-dimethyl derivative (dmtp) have been isolated and structurally characterized. Five of them are mononuclear and contain 1,10-phenanthroline (phen) or ethylenediamine (en) as auxiliary ligands, their formula being [Cu(H₂O)(phen)(tp)₂](ClO₄)₂ · H₂O, [Cu(H₂O)(phen)(dmtp)₂](ClO₄)₂, [Cu(NO₃)(H₂O)(phen)(tp)](NO₃), [Cu(H₂O)₂(en)(tp)₂](ClO₄)₂ and [Cu(H₂O)₂(en)(dmtp)₂](ClO₄)₂. In all these compounds the tp or dmtp ligand is monodentately coordinated via the nitrogen atom in position 3. The auxiliary ligand influences the coordination number, which is five when this ligand is phen and six when it is en whereas the number of triazolopyrimidine ligands linked to the metal seems to be influenced by the nature of the counteranion. A dinuclear compound with tp has also been isolated, its formula being [Cu₂(OH)(H₂O)_2.5(tp)₅](ClO₄)₃·(H₂O)_1.5, with both metal atoms linked by an hydroxydo group and by a tp bridging ligand, coordinated to one of the copper atoms via N3 and to the other via N4. This compound has several unusual features among the metal complexes with triazolopyrimidine derivatives: the presence of two different kinds of bridging moieties, the coexistence of bridging and terminal ligands and the formation of a N3–N4 bridge for a Cu(II) dinuclear compound for a derivative without exocyclic oxygen atoms.     

Ternary Ni(II) and Cu(II) complexes with 4,6-dimethyl-1,2,3-triazolo-[4,5-d]pyrimidin-5,7-dionato and chelating aliphatic amines as auxiliary ligands: Variability in the binding site and hydrogen-bond networks

Nickel(II) and copper(II) complexes bearing the anionic form of 4,6-dimethyl-1,2,3-triazolo-[4,5-d]pyrimidin-5,7-dione (dmax⁻) and one of the aliphatic amines ethylenediamine (en), 1,3-diaminopropane (dap) or 1,3-bis-(3-aminopropyl)-amine (bapa) have been synthesized and characterized. The crystal structures of Ni-en, Cu-en and Cu-bapa compounds have been solved by X-ray diffraction whereas only partial data are available for the Cu-dap compound. The binding site for the heterocycle is the triazole nitrogen atom furthest from the pyrimidine ring (N2), except for the copper(II) compound with en as auxiliary ligand, for which the bond is established through N1, this binding site being unprecedented for azaxanthine derivatives. Hydrogen atoms of amine groups and interstitial water molecules form hydrogen bonds that are involved both in the first and in the second coordination spheres. In the first, N(amine)–H links to acceptor atoms of dmax⁻ stabilize the complexes, probably conditioning, together with the Jahn–Teller distortion, the unusual N1 link in the Cu-en compound. In the second sphere, two-dimensional networks are formed with interstitial water molecules acting as the “main glue”.     

Synthesis of 1,2,4-Triazol-3-ylmethyl-, 1,3,4-Oxa-, and -Thiadiazol-2-ylmethyl-1<Emphasis Type="Italic">H</Emphasis>-[1,2,3]-triazolo[4,5-<Emphasis Type="Italic">d</Emphasis>]pyrimidinediones

Summary. 1-Carbethoxymethyl-4,6-dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-5,7(4H,6H)-dione was synthesized and treated with hydrazine hydrate to give the corresponding hydrazide. The latter hydrazide was treated either with phenylisothiocyanate or with carbon disulfide/alc. KOH to afford the corresponding thiosemicarbazide and oxadiazole derivatives. Alkylation of 2-mercapto-1,3,4-oxadiazole with dimethyl sulfate or ethyl chloroacetate gave the corresponding 2-methylthio-, and 2-ethylthioglycolate derivatives. Formation of 1,3,4-thiadiazole, 5-mercapto-1,2,4-triazole, and 1,3,4-oxadiazole were carried out by treating of the latter thiosemicarbazide with conc. H₂SO₄, NaOH/HCl, and HgO. Treating of 5-mercapto-1,2,4-triazole with ethyl chloroacetate afforded the thioglycolate ester. Hydrolysis of the latter with hydrazine hydrate afforded the hydrazide derivatives. Condensation of these hydrazides with monosaccharide aldoses gave the corresponding sugar hydrazones. The novel compounds were tested for antiviral activity against hepatitis B virus and showed moderate activities.     

Synthesis and structure of condensed triazolo- and tetrazolopyrimidines

Herein we present the synthesis of several new hydrazino derivatives of cyclopenta[c]pyridine, 5,6,7,8-tetrahydroisoquinoline and pyrano[3,4-c]pyridine from 3-oxo-4-cyano fused pyridine derivatives. The hydrazino derivatives obtained were used as starting materials for the synthesis of isomeric triazolopyrimidines as well as tetrazolopyrimidines. Furthermore, the rearrangement of triazolopyrimidines 7 into triazolopyrimidines 8 is also presented. In DMSO tetrazolopyrimidines 10 were shown to be in equilibrium with the relevant azidopyrimidines 9. The tetrazolopyrimidine structure was confirmed by X-ray crystallography. The synthesized compounds were tested for their antimicrobial activity.     

Easy access to triazoles, triazolopyrimidines, benzimidazoles and imidazoles from imidates

We have described a new and easy synthesis of triazoles, triazolopyrimidines, benzimidazoles and imidazoles variously substituted based on the reaction of imidates with diamine derivatives. The products were obtained in moderate to good yields. A general mechanism for the reactions is proposed.