SYNTHESIS AND ANTIMICROBIAL PROPERTIES OF 2H-PYRAN-3(6H)-ONE DERIVATIVES AND RELATED-COMPOUNDS

The synthesis of several derivatives of 2H-pyran-3(6H)-ones and their Michael adducts is described. Phenylthio, benzenesulfonyl, p-acetylaminobenzenesulfonyl, and p-bromophenyl substituents are beneficial for activity against gram-positive bacteria. 2-[4-(Phenylthio) phenyl]-2-methyl-6-methoxy-2H-pyran-3(6H)-one (8a) showed a minimum inhibitory concentration of 1.56 mug/mL against Staphylococcus aureus ATCC 2593, and 2-[4-(phenylthio)phenyl]-2-methyl-6-[(p-nitrobenzoyl)oxy]-2H-pyran-3 (6H)-one (9) showed a minimum inhibitory concentration of 0.75 mug/mL against Streptococcus sp. C203M. In general, derivatives of 6-hydroxy-2H-pyran-3(6H)-ones with substituents at C-2 and C-6 showed significant activity against gram-positive bacteria. More specifically, the bulkier the C-2 substituent, the greater the antibacterial activity. Michael adducts of thiols (13) showed activity, which may be due to a retro-Michael reaction. In conclusion, the alpha,beta-enone system is essential for the activity of 6-hydroxy-2H-pyran-3(6H)-ones, and the size and nature of substituents at C-2 are associated with antimicrobial activity

One-pot synthesis, characterization, and antioxidant capacity of sulfur- and oxygen-substituted 1,4-naphthoquinones and a structural study

In the present study, we reported the one-pot synthesis of S,S- and S,O-substituted 1,4-naphthoquinones, their structural studies, and investigation of their antioxidant activity. The multicomponent reactions of 2,3-dichloro-1,4-naphthoquinone with sulfur- and oxygen-containing nucleophiles were investigated to obtain highly functionalized S,S- and S,O-substituted 1,4-naphthoquinone derivatives. All new compounds were characterized on the basis of H-1, F-19, and C-13 nuclear magnetic resonance spectroscopy, mass spectrometry, and Fourier transform infrared spectroscopy. Crystal structure of 2,3-dihydro-2-(hydroxymethyl)naphtho[2,3-b]-1,4-oxathiin-5,10-dione was determined by X-ray diffraction method. The synthesized compounds were screened for their antioxidant capacity and free radical scavenging activity using the cupric reducing antioxidant capacity method and DPPH method, respectively. 3-Chloro-2-[3-(3-chloro-1,4-dihydro-1,4-dioxonaphthalen-2-yloxy)propylsulfanyl]-1,4-naphthoquinone shows the highest antioxidant capacity with 0.63 cupric reducing antioxidant capacity-trolox equivalent antioxidant capacity coefficient