Iodine-PEG as a unique combination for the metal-free synthesis of flavonoids through iodonium-triiodide ion-pair complexation

An efficient metal-free single-step protocol has been developed for the direct synthesis of flavones from 2-hydroxyacetophenone and substituted benzaldehydes. This chemical transformation is exclusively promoted by the iodonium-triiodide ion couple formed through iodine and PEG-400 complexation. The triiodide anion not only helps in the abstraction of a proton from the acetophenone but also promotes the cyclization of intermediate chalcone to the corresponding flavones. The flavones were obtained in very high yields without using any toxic metal catalysts or harsh reaction conditions. The reaction mechanism was established through a series of test reactions and entrapping of reaction intermediates. The developed protocol provides direct access to flavones in high yields under milder reaction conditions with great substrate compatibility, including hydroxylated derivatives.

Synthesis and in vitro inhibition effect of new pyrido[2,3-d]pyrimidine derivatives on erythrocyte carbonic anhydrase I and II

In vitro inhibition effects of indolylchalcones and new pyrido[2,3-d]pyrimidine derivatives on purified human carbonic anhydrase I and II (hCA I and II) were investigated by using CO2 as a substrate. The results showed that all compounds inhibited the hCA I and hCA II enzyme activities. Among all the synthesized compounds, 7e (IC50 = 6.79 µM) was found to be the most active compound for hCA I inhibitory activity and 5 g (IC50 = 7.22 µM) showed the highest hCA II inhibitory activity. Structure-activity relationships study showed that indolylchalcone derivatives have higher inhibitory activities than pyrido[2,3-d]pyrimidine derivatives on hCA I and hCA II. Additionally, methyl group bonded to uracil ring increases inhibitory activities on both hCA I and hCA II.

Synthesis of functionalized 2-aryl-4-(indol-3-yl)-4H-chromenes via iodine-catalyzed domino Michael addition-intramolecular cyclization reaction

An efficient synthesis of novel functionalized 2-aryl-4-(indol-3-yl)-4H-chromenes has been developed, in the presence of a catalytic amount of iodine, from easily available starting materials, 2-hydroxychalcone derivatives. Indole, substituted indoles and 7-azaindole are suitable for this transformation. The possible domino Michael addition-intramolecular cyclization reaction mechanism is proposed.

Synthesis and structure elucidation of five new conjugates of oleanolic acid derivatives and chalcones using 1D and 2D NMR spectroscopy

Five new conjugates of oleanolic acid derivatives and chalcones have been designed and synthesized. The structure elucidation of these conjugates was accomplished by using extensive 1D ((1)H, (13)C) and 2D NMR spectroscopic studies (COSY, HSQC and HMBC); and α-glucosidase inhibitory activity is reported for these conjugates. Compound 2b (IC(50)  = 47.5 µm) displayed much stronger activity than oleanolic acid and acarbose.