Synthesis and antibacterial activities of cyclodimers of styrene oxides

A simple synthetic procedure for preparation of 1,4-dioxanes or 1,3-dioxolanes from styrene oxides is described. Electron-donating groups on the aromatic ring of the styrene oxides were found to favour formation of 1,4-dioxanes while electron-withdrawing groups favoured formation of 1,3-dioxolanes. Antibacterial activities of the prepared cyclodimers are reported. KEY WORDS: Dioxanes, Dioxolanes, Styrene, Epoxidation, Cyclodimerization, Antibacterial activities Bull. Chem. Soc. Ethiop. 2011, 25(2), 299-304

FACILE ENANTIOSELECTIVE PALLADIUM CATALYSED TRANSFER HYDROGENATION OF α-METHYLCINNAMIC ACID IN THE PRESENCE OF OPTICAL PURE ORGANIC ACIDS

An efficient and enantioselective method for catalytic transfer hydrogenation of the C=C double bond of α-methylcinnamic acid with the aid of chiral organic acids as the hydrogen donors and palladium(II) chloride as the catalyst is reported. Enantiomeric excess was assayed using optical rotation measurements. The best stereoselectivity was achieved when L-(+)-tartaric acid was used as the hydrogen donor and acetonitrile as the solvent. KEYWORDS: Enantioselective, Chiral, α-Methylcinnamic acid, Transfer hydrogenation, Palladium(II) chloride Bull. Chem. Soc. Ethiop. 2007, 21(3), 457-460

Chemical constituents of the root wood of Erythrina sacleuxii and determination of the absolute configuration of suberectin

Phytochemical investigation on the root wood of Erythrina sacleuxii (Leguminosae) led to the isolation of nine secondary metabolites (1-9). Compound 1 was isolated from the genus Erythrina for the first time. The pure compounds were identified on the basis of comprehensive spectroscopic and spectrometric analyses, while their absolute configurations were determined based on chiroptical measurements. Compounds 5 and 6 showed weak antifungal activity against Pyricularia oryzae with MIC values of 20 µg/mL.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 135-140. DOI: https://dx.doi.org/10.4314/bcse.v34i1.1

Efficient and Green Preparation of 2-Amino-4H-chromenes by a Room-Temperature, Na₂CO₃-Catalyzed, Three-Component Reaction of Malononitrile, Benzaldehydes, and Phloroglucinol or Resorcinol in Aqueous Medium

<div><p></p><p>The preparation of substituted 2-amino-4H-chromenes by a Na₂CO₃-catalyzed reaction of malononitrile, benzaldehydes, and phloroglucinol or resorcinol in aqueous medium and at room temperature is reported. The merits of this procedure include limited use of organic solvents, easy workup technique, and high purity of products. The 2-amino-4H-chromenes were prepared in yields of 54–96%.</p></div

Fast and efficient synthesis of flavanones from cinnamic acids

<p>A fast and efficient synthesis of flavanones from cinnamic acids in three steps has been developed. First, the cinnamic acid was converted to cinnamyol chlorides using SOCl₂. The acid chlorides were then treated with substituted phenols in BF₃ · OEt₂ to furnish corresponding chalcones in 42(75% yields. Base-catalyzed cyclization of the chalcones at room temperature afforded corresponding flavones in 85–95% yields. The conversion of the cinnamic acid derivatives to corresponding chalcones was found to be sensitive to the position and nature of the substituents on the aromatic rings.</p

New isoflavan from <i>Erythrina livingstoniana</i>

Chemical investigation of the root wood of Erythrina livingstoniana led to the isolation of one previously undescribed isoflavan (3S,3″R)-7-hydroxy-2′-methoxy-[3″-hydroxy-2″,2″-dimethylpyrano (3′,4′)] isoflavan 1, together with eleven known compounds 2-12. The structure of compound 1 was elucidated on the basis of extensive spectroscopic and spectrometric analyses (1 D and 2 D-NMR and APCI-HRMS), with absolute configurations established by comparison of experimental and DFT calculated ECD data. The assignment of the absolute configurations of C-3 and C-3″ of compounds 2 and 3, respectively, were reported for the first time. Compounds 1 − 4 were evaluated for their antibacterial activities in vitro against E. coli ATCC 25922 and S. aureus ATCC 25923. Compound 1 exhibited moderate antibacterial activity with MIC value of 0.063 mg/mL against the clinically relevant risk-group 2 (RG-2) bacterium S. aureus.</p