Synthesis of New Pyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines and Their Use in the Preparation of Tetraheterocyclic Systems

8,10-Dimethyl-3-(unsubstituted, methyl, ethyl, n-butyl, phenyl)-4-hydroxypyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidin-2(1H)-ones and 3-(2-hydroxyethyl)-2,8,10-trimethylpyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidin-4-ol were synthesized by cyclocondensation of 3-amine-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine with ethyl malonates and α-acetyl-γ-butyrlolactone. Dichloro- and diazido- derivatives were obtained from the reaction of pyridopyrazlopyrimidine derivatives with POCl₃ followed by NaN₃. The tetrahetrocyclic systems were formed by cyclization of 4-chloro-3-(2-chloroethyl)-2,8,10-trimethylpyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidine with the appropriate primary amines. The structures of all compounds were established by NMR and mass spectra.     

Construction of 1,3-disubstituted 4-oxo-1,4-dihydroquinolines as a potential antibacterial agents

Research on Chemical Intermediates - A novel series of 1,3-disubstituted 4-oxo-1,4-dihydroquinolines as antimicrobial agents were designed and synthesized. Their structures have been confirmed...     

Synthesis of 1,2,4-Triazol-3-ylmethyl-, 1,3,4-Oxa-, and -Thiadiazol-2-ylmethyl-1H-[1,2,3]-triazolo[4,5-d]pyrimidinediones

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 of some fused heterocycles based on thieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine and their antimicrobial activity

The reaction of 3-amino-4,6-dimethylthieno[2,3-b]pyridine-2-carbonitrile with ethylenediamine in the presence of a catalytic amount of carbon disulfide afforded 2-(4,5-dihydro-1H-imidazol-2-yl)-4,6-dimethylthieno-[2,3-b]pyridine-3-amine while its reaction with triethyl orthoformate followed by the reaction with hydrazine hydrate gave 4-imino-7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d]pyrimidine-3(4H)-amine. These two derivatives underwent cyclocondensation reactions with commercially available reactants to afford new heterocycles containing the thieno[2,3-b]pyridine moiety. Some of the synthesized derivatives were tested for antimicrobial and antifungal activity.     

Synthesis and antiviral evaluation of new 2,5-disubstituted 1,3,4-oxadiazole derivatives and their acyclic nucleoside analogues

Abstract  

A number of new 5-[(naphthalen-1-yloxy)-methyl]-1,3,4-oxadiazole derivatives were synthesized. Sugar 2-[5-[(naphthalen-1-yloxy)methyl]-1,3,4-oxadiazol-2-ylthio]acetohydrazones were prepared by condensation of the hydrazide with the corresponding monosaccharides. Cyclization of the sugar hydrazones with acetic anhydride afforded the substituted oxadiazoline derivatives. The synthesized compounds displayed different degrees of antiviral activities or inhibitory actions against HCV and HIV viruses.     

Synthesis of Novel 3-Substituted Pyridothienopyrimidine Derivatives with Biological Evaluation as Antimicrobial Agents

Novel 3-substituted pyridothienopyrimidine derivatives have been synthesized via the reaction of 2-{7,9-dimethyl-4-oxopyrido[3',2':4,5]thieno[3,2-d]pyrimidin-3(4H)-yl}acetohydrazide(5) with a variety of active reagents and chemicals. Structures of the newly synthesized compounds were established based on spectral data. The resulting pyridothienopyrimidine derivatives were evaluated for their possible antimicrobial activity and some of them represent a new class of potentially antimicrobial compounds, especially compounds 9 and 18 which displayed the highest activity against Gram-positive bacteria, Gram-negative bacteria, and Fungi in MIC range of 0.12-1.95 μg/mL.     

Fused pyridothienopyrimidine heterocycles. 2*. A facile and efficient synthesis of the annelated pyrido[3′,2′:4,5]thieno-[2,3-<Emphasis Type="Italic">e</Emphasis>]pyrimido[3,2-<Emphasis Type="Italic">c</Emphasis>]pyrimidones

The cyclocondensation reactions of 4-aminopyridothienopyrimidine with malonates and their acetylation were studied. All structures were determined by ¹H NMR and mass spectra techniques.