Conjugates of Lupane Triterpenoids with Arylpyrimidines: Synthesis and Anti-inflammatory Activity

Semisynthetic triterpenoid betulonic acid is of significant interest due to its biological activity and synthetic application. In this study, we report the synthesis of hybrid compounds, containing betulonic acid carboxamide and arylpyrimidine fragments. A total of 15 conjugates were prepared using the cyclocondensation reaction of new terpenoid alkynyl ketones with amidinium salts. The main synthetic approach to betulonic acid amide-derived alkynylketones was based on the cross-coupling reaction of N-(4-ethynylphenyl)- or N-(2-(4-ethynylphenyl)-1-(methoxycarbonyl)ethyl)- substituted betulonic acid carboxamide with aroylchlorides. Cyclocondensation of alkynones with amidine or guanidine hydrochlorides by reflux in MeCN in the presence of K₂CO₃ led to the formation of terpenoid pyrimidine hybrids in 52-89% isolated yield. Anti-inflammatory properties of new type of triterpenoid-pyrimidine conjugates were studied using the histamine- and concanavalin A- induced mouse paw edema models. In a model of acute inflammation betulonic acid amide-arylpyrimidines containing a 4-fluorophenyl substituent at the C-6 position of pyrimidine ring exhibited significant and selective anti-inflammatory activity. Compounds containing the 4-bromophenyl- substituent in the pyrimidine ring revealed selective anti-inflammatory activity in the model of immunogenic inflammation (concanavalin-A model). It should be noted that the methoxycarbonyl substituted ethane link between pharmacophore ligands (betulonic acid carboxamide and arylpyrimidine) has a significant effect on anti-inflammatory activity in both in vivo models of inflammation. It was shown by molecular docking that the new derivatives are incorporated into the binding site of the protein Keap1 Kelch-domain by their pyrimidine substituent with the formation of more non-covalent bonds.

An efficient protocol for the synthesis of new camphor pyrimidine and camphor thiazole derivatives using conventional and microwave irradiation techniques and in vitro evaluation as potential antimicrobial agents

BACKGROUND

A series of new pyrimidines and thiazoles containing camphor moiety were synthesized under both conventional and microwave irradiation techniques.

METHODS

The condensation of camphor either with aminoguanidine or thiosemicarbazide gives the camphor hydrazine carboximidiamide 2 and the camphor thiosemicarbazone 3, respectively. Refluxing of 3 with chloroacetonitrile afforded the camphor thiazol-4-imine 4. Compounds 2 and 4 were used as precursors for the synthesis of target products.

RESULTS

The reaction of 2 with different species such as arylidene malononitrile, acetylacetone, and ethyl acetoacetate gave the corresponding camphor pyrimidine derivatives 5a,b-7 while refluxing of compound 4 with different reagents e.g. aldehydes, isatin, ninhydrin, acetic anhydride, benzene sulphonyl chloride, and p-nitro-benzoyl chloride afforded the camphor thiazole derivatives 8a-d-13, respectively.

CONCLUSION

A comparison between the conventional way and the eco-friendly microwave irradiation method occurred in the synthesis of the same compounds, which the latter was more efficient. The elemental analysis, FT-IR, 1H NMR, 13C NMR, and Mass spectra confirm the structures of the obtained new compounds. The potential use of some selected derivatives as antimicrobial agents was investigated and gave promising results.

Antibacterial and molecular docking studies of newly synthesized nucleosides and Schiff bases derived from sulfadimidines

A new series of nucleosides, moieties, and Schiff bases were synthesized from sulfadimidine. Infrared (IR), ¹HNMR, ¹³C NMR, and mass spectrometry techniques and elemental analysis were employed to elucidate the synthesized compounds. The prepared analogues were purified by different chromatographic techniques (preparative TLC and column chromatography). Molecular docking studies of synthesized compounds 3a, 4b, 6a, and 6e demonstrated the binding mode involved in the active site of DNA gyrase. Finally, all synthesized compounds were tested against selected bacterial strains. The most effective synthesized compounds against S. aureus were 3a, 4d, 4b, 3b, 3c, 4c, and 6f, which exhibited inhibition zones of inhibition of 24.33 ± 1.528, 24.67 ± 0.577, 23.67 ± 0.577, 22.33 ± 1.528, 18.67 ± 1.528 and 19.33 ± 0.577, respectively. Notably, the smallest zones were observed for 4a, 6d, 6e and 6g (6.33 ± 1.528, 11.33 ± 1.528, 11.67 ± 1.528 and 14.66 ± 1.155, respectively). Finally, 6b and 6c gave negative zone values. K. pneumoniae was treated with the same compounds and the following results were obtained. The most effective compounds were 4d, 4c, 4b and 3c, which showed inhibition zones of 29.67 ± 1.528, 24.67 ± 0.577, 23.67 ± 1.155 and 19.33 ± 1.528, respectively, followed by 4a and 3d (15.33 ± 1.528 for both), while moderate results (13.67 ± 1.155 and 11.33 ± 1.528) were obtained for 6f and 6g, respectively. Finally, 6a, 6b, 6c, 3a, and 3b did not show any inhibition. The most effective compounds observed for the treatment of E. coli were 4d, 4b, 4c, 3d, 6e and 6f (inhibition zones of 26.33 ± 0.577, 21.67 ± 1.528, 21.67 ± 1.528, 19.67 ± 1.528, 17.67 ± 1.155 and 16.67 ± 1.155, respectively). Compounds 3b, 3c, 6a, 6c, and 6g gave moderate results (13.67 ± 1.528, 12.67 ± 1.528, 11.33 ± 0.577, 15.33 ± 1.528 and 12.67 ± 1.528, respectively), while 6b showed no effect. The MIC values against S. aureus ranged from 50 to 3.125 mg, while those against E. coli and K. pneumoniae ranged from 50 to 1562 mg. In vitro, the antibacterial effects were promising. Further research is required to study the in vivo antibacterial effects of these compounds and determine therapeutic doses.

Polysubstituted Pyrimidines as Potent Inhibitors of Prostaglandin E2 Production: Increasing Aqueous Solubility

Water solubility is one of the key features of potential therapeutic agents. In order to enhance the low water solubility of the parent 5-butyl-4-(4-methoxyphenyl)-6-phenylpyrimidin-2-amine, a potent inhibitor of prostaglandin E₂ (PGE₂ ) production, we synthesized and evaluated a new series of derivatives in which the butyl group at the C5 position of the pyrimidine ring was replaced with a less lipophilic substituent, preferably with a hydrophilic aliphatic moiety. Except for the 5-cyanopyrimidine derivative, all target compounds exhibited increased (2.7 - 87-fold) water solubility relative to the parent compound. Although nontoxic in mouse peritoneal cells, the prepared compounds were either equipotent or weaker inhibitors of PGE₂ production than the parent compound. The most promising compound from the series was found to be the 5-(2,5,8,11-tetraoxadodecyl)pyrimidine derivative (with three polyethylene glycol units at the C5 position), which exhibited 32-fold higher water solubility and only slightly weaker inhibitory activity (22 % of remaining PGE₂ production) compared with the parent compound (15 % of remaining PGE₂ production).

Research developments in the syntheses, anti-inflammatory activities and structure-activity relationships of pyrimidines

Pyrimidines are aromatic heterocyclic compounds that contain two nitrogen atoms at positions 1 and 3 of the six-membered ring. Numerous natural and synthetic pyrimidines are known to exist. They display a range of pharmacological effects including antioxidants, antibacterial, antiviral, antifungal, antituberculosis, and anti-inflammatory. This review sums up recent developments in the synthesis, anti-inflammatory effects, and structure-activity relationships (SARs) of pyrimidine derivatives. Numerous methods for the synthesis of pyrimidines are described. Anti-inflammatory effects of pyrimidines are attributed to their inhibitory response versus the expression and activities of certain vital inflammatory mediators namely prostaglandin E2, inducible nitric oxide synthase, tumor necrosis factor-α, nuclear factor κB, leukotrienes, and some interleukins. Literature studies reveal that a large number of pyrimidines exhibit potent anti-inflammatory effects. SARs of numerous pyrimidines have been discussed in detail. Several possible research guidelines and suggestions for the development of new pyrimidines as anti-inflammatory agents are also given. Detailed SAR analysis and prospects together provide clues for the synthesis of novel pyrimidine analogs possessing enhanced anti-inflammatory activities with minimum toxicity.