Radical Scavenging Activity of Ascorbic Acid Analogs Containing a Carbonyl Conjugated Ene-Diol Structure
摘要:
Small molecule antioxidants such as ascorbic acid (AscH(2)) prevent the oxidative damage of biological molecules by scavenging reactive oxygen species. A carbonyl-conjugated ene-diol structure is essential for the antioxidant activity of AscH(2). As such, we synthesized novel AscH(2) analogs containing a carbonyl conjugated ene-diol structure and evaluated their radical scavenging activities. When the 1,2-dihydroxyethyl group was removed, radical scavenging activity equal to AscH(2) was observed. Analogs containing an endocyclic nitrogen atom instead of a ring oxygen displayed higher radical scavenging activities than AscH(2). Therefore, the electron donating effect of the carbonyl conjugated ene-diol structure greatly increased the radical scavenging activity of AscH(2) analogs.
Unsaturated β-ketoesters as versatile electrophiles in organocatalysis
作者:Susy Piovesana、Daniele M. Scarpino Schietroma、Ludovico G. Tulli、Mattia R. Monaco、Marco Bella
DOI:10.1039/c003296d
日期:——
Beta-ketoesters, which have widely been employed as nucleophiles, are also useful electrophiles in organocatalytic quinine mediated cascade reactions, leading to the formation of products bearing multiple stereocenters in high stereoselectivity.
Michael addition of chiral formaldehyde N,N-dialkylhydrazones to activated cyclic alkenes
作者:Juan Vázquez、Elena Cristea、Elena Díez、José M. Lassaletta、Auxiliadora Prieto、Rosario Fernández
DOI:10.1016/j.tet.2005.02.007
日期:2005.4
The nucleophilic conjugate addition of chiral formaldehydeN,N-dialkylhydrazones 1 to doubly activated cyclic alkenes 2–8 proceeds smoothly to afford the corresponding Michael adducts 14, 16, 18, 20, 22, 24, and 25 in variable yields and selectivities. The reactions take place either spontaneously or in the presence of MgI2 as a mild Lewis acid depending on the type of substrate. Release of the chiral
Single oxygen reacts with 1-acetyl-2-methoxycyclopentene () to give the unsaturated hemiperketal . decomposes by an intermolecular oxygen atom transfer to give the epoxy-β-diketone . Several β-alkoxyenones which are held in the s- conformation failed to react with singletoxygen.