Treatment of phenols with ninhydrin in acidic medium afforded 2-hydroxy-2-(ortho-hydroxy-phenyl/naphthyl)-1,3-dioxoindanes, which being unstable were isolated in their hemiketal forms. These synthesized compounds were subjected to TLC screening for radical scavenging and in vitro lipoxgenase and cycloxygenase enzyme inhibition assays. The best compound was identified and studied in detail for steady-state and time-resolved free radical kinetics, viz., DPPH, ABTS(.-), (OH)-O-. and rate constants for these reactions were evaluated. The best compound was also subjected to in vivo anti-inflammatory and analgesic activities in which the compound showed good promise for further structural optimization. (c) 2006 Elsevier Ltd. All rights reserved.
A biomimetic synthesis of (−)-ascorbyl phloroglucinol and studies toward the construction of ascorbyl-modified catechin natural products and analogues
作者:Sneha A. Belapure、Zachary G. Beamer、John E. Bartmess、Shawn R. Campagna
DOI:10.1016/j.tet.2011.09.102
日期:2011.12
A method for appending the ascorbyl moiety onto the framework of phenolic natural products has been developed. This reaction proceeds in two steps from.-ascorbic acid and employs acetic acid catalysis. Excellent stereoselectivity is observed during C C bond formation between the phenolic compound and dehydroascorbic acid, and the process is also chemoselective for phenol derivatives bearing electron-donating substituents in each of the 1, 3, and 5 positions. Further, good regioselectivity was also observed when phenols lacking an axis of C-2 symmetry were employed. This method has led to the synthesis of (-)-ascorbyl phloroglucinol as well as the tetracyclic core of ascorbyl-modified catechin natural products. (C) 2011 Elsevier Ltd. All rights reserved.